U.S. patent application number 16/753249 was filed with the patent office on 2020-12-03 for systems and methods for micropatterning objects.
The applicant listed for this patent is Cornell University. Invention is credited to Seyedhamidreza Alaie, Simon Dunham, James K. Min, Amir Ali Amiri Moghadam, Bobak Mosadegh.
Application Number | 20200376740 16/753249 |
Document ID | / |
Family ID | 1000004990190 |
Filed Date | 2020-12-03 |
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United States Patent
Application |
20200376740 |
Kind Code |
A1 |
Alaie; Seyedhamidreza ; et
al. |
December 3, 2020 |
SYSTEMS AND METHODS FOR MICROPATTERNING OBJECTS
Abstract
Implanted medical devices need a mechanism of immobilization to
surrounding tissues, which minimizes tissue damage while providing
reliable long-term anchoring. This disclosure relates to techniques
for patterning arbitrarily shaped 3D objects and to patterned
balloon devices having micro- or nano-patterning on an outer
surface of an inflatable balloon. The external pattern can provide
enhanced friction and anchoring in an aqueous environment. Examples
of these types of patterns are hexagonal arrays inspired by tree
frogs, corrugated patterns, and microneedle patterns. The patterned
balloon devices can be disposed between an implant and surrounding
tissues to facilitate anchoring of the implant.
Inventors: |
Alaie; Seyedhamidreza; (New
York, NY) ; Dunham; Simon; (Ithaca, NY) ;
Mosadegh; Bobak; (Ithaca, NY) ; Min; James K.;
(Ithaca, NY) ; Moghadam; Amir Ali Amiri; (New
York, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cornell University |
Ithaca |
NY |
US |
|
|
Family ID: |
1000004990190 |
Appl. No.: |
16/753249 |
Filed: |
October 3, 2018 |
PCT Filed: |
October 3, 2018 |
PCT NO: |
PCT/US2018/054233 |
371 Date: |
April 2, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62567625 |
Oct 3, 2017 |
|
|
|
62567644 |
Oct 3, 2017 |
|
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29K 2083/00 20130101;
B29C 33/40 20130101; B29K 2875/00 20130101; B29C 33/56 20130101;
B29C 59/021 20130101; B29C 2037/0035 20130101; G03F 7/0002
20130101; B29C 2059/023 20130101; B29C 37/0032 20130101; B29C
59/022 20130101; B29C 59/06 20130101; B29C 2033/426 20130101; A61M
2025/1031 20130101; A61M 25/1027 20130101; B29C 33/424
20130101 |
International
Class: |
B29C 59/02 20060101
B29C059/02; B29C 59/06 20060101 B29C059/06; B29C 33/40 20060101
B29C033/40; B29C 33/42 20060101 B29C033/42; B29C 33/56 20060101
B29C033/56; G03F 7/00 20060101 G03F007/00; A61M 25/10 20060101
A61M025/10; B29C 37/00 20060101 B29C037/00 |
Claims
1. A method of patterning an object, comprising: providing a
three-dimensional (3D) object; wrapping the 3D object in a flexible
stamp having a micropattern on its surface; inserting the 3D object
and the flexible stamp into a vacuum bag; applying vacuum to the 3D
object and the flexible stamp within the vacuum bag; and
transferring the micropattern of the flexible stamp to a surface of
the 3D object.
2. The method of claim 1, further comprising: micropatterning a
rigid material via photolithography; and fabricating the flexible
stamp having the micropattern on its surface using the
micropatterned rigid material;
3. The method of claim 2, further comprising fabricating the
flexible stamp by: inverting the micropatterned rigid material to
form a soft template having the micropattern on its surface;
coating the soft template with an elastomeric material; curing the
elastomeric material to form the flexible stamp; and peeling the
flexible stamp off of the soft template.
4. The method of claim 3, wherein the soft template comprises
silicone.
5. The method of claim 3, further comprising applying a treatment
to a surface of the soft template.
6. The method of claim 5, wherein the surface treatment comprises
trichloro perfluoro silane.
7. The method of claim 1, wherein the flexible stamp comprises an
elastomeric film.
8. The method of claim 7, wherein the flexible stamp has a
thickness between 20 and 500 microns.
9. The method of claim 1, wherein the micropattern has a thickness
between one microns and 40 microns.
10. The method of claim 1, wherein the 3D object is formed from at
least one of silicone, nitinol alloy, and polyurethane.
11. The method of claim 1, further comprising treating a surface of
the 3D object to promote adhesion of the flexible stamp to the 3D
object.
12. A micropatterned object formed by performing steps comprising:
providing a three-dimensional (3D) object; wrapping the 3D object
in a flexible stamp having a micropattern on its surface; inserting
the 3D object and the flexible stamp into a vacuum bag; applying
vacuum to the 3D object and the flexible stamp within the vacuum
bag; and transferring the micropattern of the flexible stamp to a
surface of the 3D object.
13-41. (canceled)
42. The object of claim 12, formed by further performing steps
comprising: micropatterning a rigid material via photolithography;
and fabricating the flexible stamp having the micropattern on its
surface using the micropatterned rigid material.
43. The object of claim 42, wherein the flexible stamp is
fabricated by: inverting the micropatterned rigid material to form
a soft template having the micropattern on its surface; coating the
soft template with an elastomeric material; curing the elastomeric
material to form the flexible stamp; and peeling the flexible stamp
off of the soft template.
44. The object of claim 43, wherein the soft template comprises
silicone.
45. The object of claim 43, formed by further performing a step of
applying a treatment to a surface of the soft template.
46. The object of claim 45, wherein the surface treatment comprises
trichloro perfluoro silane.
47. The object of claim 12, wherein the flexible stamp comprises an
elastomeric film.
48. A method of patterning an object, comprising: micropatterning,
via photolithography, a rigid material with a micropattern;
fabricating a flexible stamp having the micropattern on its surface
by: inverting the micropatterned rigid material to form a soft
template having the micropattern on its surface; applying a
treatment to a surface of the soft template; coating the soft
template with an elastomeric material; curing the elastomeric
material to form the flexible stamp; and peeling the flexible stamp
off of the soft template; wrapping a three-dimensional (3D) object
in the flexible stamp; inserting the 3D object and the flexible
stamp into a vacuum bag; applying vacuum to the 3D object and the
flexible stamp within the vacuum bag; and transferring the
micropattern of the flexible stamp to a surface of the 3D
object.
49. The method of claim 48, wherein the surface treatment comprises
trichloro perfluoro silane.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to International
Patent Application No. PCT/US18/54233, filed Oct. 3, 2018 and
titled "SYSTEMS AND METHODS FOR MICROPATTERNING OBJECTS," which
claims priority to U.S. Provisional Patent Application No.
62/567,625, filed Oct. 3, 2017 and titled "MICROPATTERNED BALLOONS
AND METHODS OF FABRICATION," and to U.S. Provisional Patent
Application No. 62/567,644, filed Oct. 3, 2017 and titled "THIN
INFLATABLE ACTUATORS AND METHODS OF CONSTRUCTION," each of which is
incorporated herein by reference in its entirety.
FIELD
[0002] The subject matter disclosed herein generally relates to the
field of medical devices and more specifically to method and
composition of friction patterning of medical devices.
BACKGROUND
[0003] Micro-patterning can provide a powerful means for
engineering surface properties, such as friction, adhesion, and
biocompatibility, with promise for medical device applications.
While soft lithography allows for micropatterning on curved
surfaces, there are limitations to the level of curvature and
object complexity achievable.
[0004] Medical implants are devices or tissues that are placed
inside or on the surface of the body. Many implants are
prosthetics, intended to replace missing body parts. Other implants
deliver medication, monitor body functions, or provide support to
organs and tissues. Some implants are made from skin, bone or other
body tissues. Others are made from metal, plastic, ceramic or other
commercially available materials. Implants can be placed
permanently or they can be removed once they are no longer needed.
For example, stents or hip implants are intended to be permanent.
However, chemotherapy ports or screws to repair broken bones can be
removed when they no longer needed.
[0005] Many implanted medical devices use wires or wireless
radiofrequency telemetry to communicate with circuitry outside the
body. However, the wires are a common source of surgical
complications, including breakage, infection and electrical noise.
In addition, radiofrequency telemetry requires large amounts of
power and results in low-efficiency transmission through biological
tissue. Therefore, there is a movement in the field to harness the
conductive properties of the body to enable wireless communication
between implanted devices and external devices.
[0006] There are considerable risks associated with medical device
implantation, including surgical risks during placement or removal,
infection, and implant failure. Depending on the type of implant,
the complications may vary in their nature and severity. Some
patients also experience reactions to the materials used in implant
manufacture. Additionally, over time, the implant can move, break,
or stop working properly. This may require additional surgery to
repair or replace the implant. Furthermore, the interaction between
the implant and the tissue surrounding the implant can lead to
complications such as implant-induced blood coagulation.
SUMMARY
[0007] This disclosure relates in part to techniques for
micropatterning surfaces of three-dimensional (3D) objects. The
techniques disclosed herein can be used for a variety of
micropatterns, materials, and devices. In some implementations, the
principles of soft lithography for fabrication of flexible
templates can be integrated with the principles of vacuum bagging,
for transfer of the patterns on arbitrary shaped nonplanar objects.
The technique is demonstrated herein with a variety of materials
including silicones, polyurethanes, and Nitinol, which are
ubiquitous in medical devices, due to their mechanics,
biocompatibility, and hemocompatibility. Micro-patterns inspired by
shark skin riblets and tree frogs are demonstrated. The flexibility
of these techniques is demonstrated by transferring patterns to
various objects/devices, including 3D printed objects, soft robotic
grippers, guidewires, and balloon catheters.
[0008] The subject matter disclose herein also relates to a
patterned balloon device including a balloon, which can be radially
expanded from a deflated state with a first volume to an inflated
state with a second volume greater than the first volume. In some
implementations, the balloon has an outer surface wherein at least
a portion of the outer surface comprises features arranged in a
pattern. In some implementations, the pattern can increase the
friction forces between the patterned balloon device and
surrounding surfaces it comes in contact with. The patterned
balloon device can reduce the likelihood of implant displacement
within a subject's body, which can reduce the need for following
surgical interventions and implant replacement. The surrounding
surfaces can be the surface of an object, tissues, organs, any
medical devices. In some implementations, the patterned balloon
device is incorporated in the body of a medical implant and
functions to secure or anchor the implant inside a subject's
body.
[0009] In some implementations, the featured arranged in a pattern
enhance friction with the application of pressure between tissues
and the patterned surface of the balloon as shown and/or move fluid
away from the interface between the patterned balloon surface and
tissues, and/or deforms or penetrates tissues to increase surface
area or provide mechanical interlocking. The pattern can be a
hexagonal array. The pattern can also include cylindrical,
rectangular, spherical, polygonal, triangular, circular, and
ellipsoid features or any geometrical shape suitable for increasing
contact friction or any combination thereof. In some
implementations, the pattern is a corrugated pattern, which can
deform tissues increasing the surface area of contact. The pattern
can be a micro- or nano-pattern depending on the size of an
individual feature in the pattern. In some implementations, the
pattern covers at least a portion of the outer surface of the
balloon.
[0010] The volumetric shape of the expandable balloon in an
inflated state can conform to the contours of surrounding surfaces.
The balloon can include a valve that is configured to enable
passing of inflation fluid in a first direction into an interior of
the balloon. The patterned balloon device can include inflation
fluid. The inflation fluid can be introduced into the interior of a
balloon through a lumen, which can gain access to the interior
lumen of the balloon. The valve may substantially prevent the
inflation fluid from moving in a second direction opposite to the
first direction. The inflation fluid can be configured to fill the
interior volume of the balloon to expand the balloon from a
deflated state to an inflated state. The inflation fluid can be a
curable fluid. The inflation fluid can be configured to cure upon
an exposure to one of an ultraviolet energy or a thermal energy.
The inflation fluid can include at least one of an epoxy,
polyethylene glycol, or a collagen-based polymeric gel. The
inflation fluid can include at least one of saline and a
self-expanding foam.
[0011] In some implementations, the patterned balloon device can be
a subject-specific patterned balloon device and the balloon can be
manufactured to fit the curvature of a specific body cavity upon
expansion where the implant is to be positioned. The patterned
balloon device can include one or more lobes. In some
implementations, a first lobe can include a first volumetric shape
and a second lobe can include a second volumetric shape that is
different than the first volumetric shape. The patterned balloon
device can include a first lobe with a first axis and a second lobe
with a second axis that is askew from the first axis.
[0012] The subject matter disclosed herein also relates to a method
of fabrication of a patterned balloon device. The method includes
fabricating a thin-walled balloon by means known in the art such as
blow molding, dip coating, vacuum bagging, or conventional molding
or casting or a combination thereof. In some implementations, the
balloon is prefabricated in the shape desired for the application
and may be subject-specific. In some implementations, the pattern
can be embossed in the outer surface of the balloon. In some other
implementations, the pattern can be fabricated on a planar template
generating a pattern master. The pattern can then be transferred to
the surface of the balloon or it can be transferred to an
elastomeric material which can be attached to the outer surface of
the balloon.
[0013] The subject matter disclosed herein further relates to a
method for immobilizing a medical implant in a body cavity
including deploying an expandable patterned balloon device in the
body cavity. The patterned balloon device includes an array of
features arranged in a pattern, which can increase friction between
the implant and surrounding tissues, thus, facilitating
immobilization of the implant. The features can be a plurality of
geometric shapes and can be disposed on at least a portion of the
outer surface of the patterned balloon device. The patterned
balloon device can further include a plurality of lobes. A
volumetric shape of the patterned balloon device in an inflated
state can be configured to complement the curvature of surrounding
tissue surfaces. The patterned balloon device can include a valve
that is configured to enable a lumen to pass into an interior
volume of the patterned balloon device in a first direction and
substantially prevent an inflation fluid from flowing in a second
direction that is opposite the first direction. The method can
include filling the expandable balloon with an inflation fluid or
gas. The inflation fluid or gas can be configured to fill the
interior volume of the expandable balloon to expand the patterned
balloon device from a deflated state to an inflated state. The
method can include anchoring the patterned balloon device to a
tissue surface.
[0014] In some implementations, the method can include removing the
lumen from the valve. The valve can include a polymeric septum that
is configured to seal a location pierced by the lumen. The method
can include curing the inflation fluid by exposing the inflation
fluid to at least one of an ultraviolet energy or a thermal energy.
The inflation fluid can include at least one of an epoxy,
polyethylene glycol or a collagen-based polymeric gel. The
inflation fluid can include at least one of saline and a
self-expanding foam. The first lobe can include a first volumetric
shape and the second lobe can include a second volumetric shape
that is different than the first volumetric shape. The patterned
balloon device can include there of more lobes. The patterned
balloon device can include the first lobe with a first axis and the
second lobe with a second axis that is askew from the first
axis.
[0015] Another aspect of the present disclosure relates to a method
for patterning an object. The method may include providing a 3D
object. The method may include micropatterning a rigid material via
photolithography. The method may include fabricating a flexible
stamp having a micropattern on its surface using the micropatterned
rigid material. The method may include wrapping the 3D object in
the flexible stamp. The method may include inserting the 3D object,
the flexible stamp, and a breather film into a vacuum bag. The
method may include applying vacuum to the 3D object and the
flexible stamp. The method may include transferring the
micropattern of the flexible stamp to a surface of the 3D object.
For example, the micropattern can be transferred to the surface of
the 3D object by applying heat to the 3D object, the flexible
stamp, and a breather film to cause a surface of the 3D object to
be imprinted with the micropattern of the flexible stamp.
[0016] In some implementations of the method, micropatterning the
rigid material via photolithography may include micropatterning a
silicon wafer.
[0017] In some implementations of the method, the flexible stamp
may include an elastomeric film.
[0018] In some implementations of the method, the flexible stamp
may have a thickness between 20 and 500 microns.
[0019] In some implementations of the method, the micropattern may
have a thickness between one microns and 40 microns.
[0020] In some implementations of the method, it may include
further including fabricating a flexible stamp by inverting the
micropatterned rigid material to form a soft template having the
micropattern on its surface. In some implementations of the method,
it may include coating the soft template with an elastomeric
material curing the elastomeric material to form the flexible
stamp. In some implementations of the method, it may include and
peeling the flexible stamp off of the soft template.
[0021] In some implementations of the method, the soft template may
include silicone.
[0022] In some implementations of the method, it may include
further including applying treatment to a surface of the soft
template.
[0023] In some implementations of the method, the surface treatment
may include trichloro perfluoro silane.
[0024] In some implementations of the method, the 3D object may be
formed from at least one of silicone, nitinol alloy, and
polyurethane.
[0025] In some implementations of the method, it may include
further including treating a surface of the 3D object to promote
adhesion of the flexible stamp to the 3D object.
[0026] Another aspect of the present disclosure relates a
micropatterned object. The micropatterned object can be formed by
performing a set of steps. The steps may include providing a 3D
object. The steps may include micropatterning a rigid material via
photolithography. The steps may include fabricating a flexible
stamp having a micropattern on its surface using the micropatterned
rigid material. The steps may include wrapping the 3D object in the
flexible stamp. The steps may include inserting the 3D object, the
flexible stamp, and a breather film into a vacuum bag. The steps
may include applying vacuum to the 3D object, the flexible stamp.
The breather film within the vacuum bag. The steps may include
transferring the micropattern of the flexible stamp to a surface of
the 3D object. For example, the micropattern may be transferred to
the surface of the 3D object by applying heat to the 3D object, the
flexible stamp, and a breather film to cause a surface of the 3D
object to be imprinted with the micropattern of the flexible
stamp.
[0027] Another aspect of the present disclosure relates to a method
for manufacturing an implantable device. The method may include
positioning a first portion of an inflatable balloon over a first
portion of a sacrificial core. The method may include positioning a
second portion of the inflatable balloon over a second upper
portion of the sacrificial core such that the second portion of the
inflatable balloon at least partially overlaps the first portion of
the inflatable balloon. The method may include applying vacuum to
the first portion of the inflatable balloon and the second portion
of the inflatable balloon via a vacuum bag assembly. The method may
include applying heat to the first portion of the inflatable
balloon and the second portion of the inflatable balloon to form a
thermoplastic bond between the first portion of the inflatable
balloon and the second portion of the inflatable balloon. The
method may include dissolving the sacrificial core.
[0028] In some implementations, the method may include inserting a
septum into a hole in the sacrificial core. The method may include
positioning a third portion of the inflatable balloon over the
first portion of the inflatable balloon. The method may include
positioning a fourth portion of the inflatable balloon over the
second portion of the inflatable balloon such that the fourth
portion of the inflatable balloon at least partially overlaps the
third portion of the inflatable balloon. The method may include
applying vacuum to the third portion of the inflatable balloon, the
fourth portion of the inflatable balloon, and the septum. The
method may include applying heat to the third portion of the
inflatable balloon, the fourth portion of the inflatable balloon,
and the septum to form a thermoplastic bond between the first
portion of the inflatable balloon, the second portion of the
inflatable balloon, the third portion of the inflatable balloon,
the fourth portion of the inflatable balloon, and the septum.
[0029] In some implementations of the method, it may include
wrapping the third portion of the inflatable balloon and the fourth
portion of the inflatable balloon in a micropatterned stamp prior
to applying the vacuum and the heat to the third portion of the
inflatable balloon and the fourth portion of the inflatable balloon
to impart micropatterned features on at least a portion of the
surface of the inflatable balloon.
[0030] In some implementations of the method, it may include
micropatterning a silicon wafer via photolithography. In some
implementations of the method, it may include inverting the
micropatterned silicon wafer to form a master template. In some
implementations of the method, it may include spin coating the
master template with an elastomeric material. In some
implementations of the method, it may include curing the
elastomeric material to form the micropatterned stamp. In some
implementations of the method, it may include peeling the
micropatterned stamp off of the master template.
[0031] In some implementations of the method, it may include
pressure forming a first film on a lower portion of a
three-dimensional mold to form the first portion of the inflatable
balloon. In some implementations of the method, it may include
pressure forming a second film on an upper portion of the 3D mold
to form the second portion of the inflatable balloon.
[0032] In some implementations of the method, it may include
dissolving dry pellets of a resin material. In some implementations
of the method, it may include spin coating the dissolved resin on a
flat template to form at least one of the first film and the second
film.
[0033] In some implementations of the method, the resin material
may include polyurethane.
[0034] In some implementations of the method, at least one of the
first film and the second film may have a thickness between 30
microns and 40 microns.
[0035] In some implementations of the method, it may include
constructing a 3D mold of a septum using an additive manufacturing
technique. In some implementations of the method, it may include
inverting the 3D mold on a silicone mold. In some implementations
of the method, it may include filling the silicone mold with dry
resin pellets. In some implementations of the method, it may
include applying heat and vacuum to the silicone mold and the dry
resin pellets to form the septum. In some implementations of the
method, it may include removing the septum from the silicone mold.
In some implementations of the method, it may include inserting the
septum into a hole in the sacrificial core.
[0036] In some implementations of the method, dissolving the
sacrificial core may further include puncturing the septum. In some
implementations of the method, dissolving the sacrificial core may
further include coupling the inflatable balloon to a perfusion
system. In some implementations of the method, dissolving the
sacrificial core may further include circulating water through an
interior of the inflatable balloon via the perfusion system to
dissolve the sacrificial core.
[0037] In some implementations of the method, it may include
wrapping an elastomeric string around the first portion of the
inflatable balloon and the second portion of the inflatable balloon
prior to applying heat to the first portion of the inflatable
balloon and the second portion of the inflatable balloon.
[0038] In some implementations of the method, it may include
constructing a 3D mold of the sacrificial core using an additive
manufacturing technique. In some implementations of the method, it
may include inverting the 3D mold on a silicone mold. In some
implementations of the method, it may include introducing a slurry
into the silicone mold. In some implementations of the method, it
may include applying heat and vacuum to the silicone mold to cause
the slurry to form the sacrificial core. In some implementations of
the method, it may include removing the sacrificial core from the
silicone mold.
[0039] Another aspect of the present disclosure relates to an
implantable device. The implantable device can be formed by
performing a set of steps. The steps may include positioning a
first portion of an inflatable balloon over a lower portion of a
sacrificial core. The steps may include positioning a second
portion of the inflatable balloon over an upper portion of the
sacrificial core such that the second portion of the inflatable
balloon at least partially overlaps the first portion of the
inflatable balloon. The steps may include applying vacuum to the
first portion of the inflatable balloon and the second portion of
the inflatable balloon via a vacuum bag assembly. The steps may
include applying heat to the first portion of the inflatable
balloon and the second portion of the inflatable balloon to form a
thermoplastic bond between the first portion of the inflatable
balloon and the second portion of the inflatable balloon. The steps
may include dissolving the sacrificial core.
[0040] In some implementations, the steps may include inserting a
septum into a hole in the sacrificial core. The steps may include
positioning a third portion of the inflatable balloon over the
first portion of the inflatable balloon. The steps may include
positioning a fourth portion of the inflatable balloon over the
second portion of the inflatable balloon such that the fourth
portion of the inflatable balloon at least partially overlaps the
third portion of the inflatable balloon. The steps may include
applying vacuum to the third portion of the inflatable balloon, the
fourth portion of the inflatable balloon, and the septum. The steps
may include applying heat to the third portion of the inflatable
balloon, the fourth portion of the inflatable balloon, and the
septum to form a thermoplastic bond between the first portion of
the inflatable balloon, the second portion of the inflatable
balloon, the third portion of the inflatable balloon, the fourth
portion of the inflatable balloon, and the septum.
BRIEF DESCRIPTION OF FIGURES
[0041] The figures, described herein, are for illustration purposes
only. It is to be understood that in some instances various aspects
of the described implementations may be shown exaggerated or
enlarged to facilitate an understanding of the described
implementations. In the drawings, like reference characters
generally refer to like features, functionally similar and/or
structurally similar elements throughout the various drawings. The
drawings are not necessarily to scale, and emphasis is instead
being placed upon illustrating the principles of the teachings. The
drawings are not intended to limit the scope of the present
teachings in any way. The system and method may be better
understood from the following illustrative description with
reference to the following drawings in which:
[0042] FIGS. 1A-1D show stages of construction of a general process
for patterning a 3D object.
[0043] FIG. 2 illustrates a flowchart of a method for
micropatterning a 3D object.
[0044] FIGS. 3A-3H show stages of construction of a micropatterned
3D object according to the method of FIG. 2.
[0045] FIG. 4 shows a magnified view of a hexagonal micropattern
that can be formed on the surface of a 3D object using the method
of FIG. 2.
[0046] FIG. 5 is a graph showing coefficients of friction for each
of four variations of the hexagonal pattern shown in FIG. 4.
[0047] FIG. 6 illustrates a hexagonal micropattern applied to a 3D
printed chess piece under different magnifications.
[0048] FIG. 7 illustrates various views of a micropattern applied
to a high aspect ratio wire.
[0049] FIG. 8 illustrates a view of a micropattern applied to a
high aspect ratio wire.
[0050] FIGS. 9A-9C show various views of a micropatterned Foley
catheter.
[0051] FIG. 10 shows various views of a micropatterned inflatable
star-shaped gripper made from silicone.
[0052] FIGS. 11A-11C show stages of a process for resin infusion on
a 3D object.
[0053] FIGS. 12A and 12B illustrates a setup that can be used for
resin infusion and micropatterning of a 3D object formed from
PDMS.
[0054] FIGS. 13A and 13B show a comparison between micropatterns
formed via 3D printing and conformal template vacuum bagging.
[0055] FIG. 14 shows a setup demonstrating the scalability of
vacuum bagging for patterning 3D objects.
[0056] FIG. 15 shows a nonplanar object 1500 at various levels of
magnification.
[0057] FIG. 16 shows a magnified view of a pattern transferred to
the surface of an object using conformal template vacuum
bagging.
[0058] FIG. 17 illustrates an example of a patterned balloon device
within the heart of a subject.
[0059] FIG. 18 shows an example of a pattern.
[0060] FIG. 19 shows an example of a corrugated pattern.
[0061] FIG. 20A illustrates a cross-sectional view of an example
patterned balloon device in an uninflated state.
[0062] FIG. 20B illustrates a cross-sectional view of an example
patterned balloon device in an inflated state.
[0063] FIGS. 21A-21C illustrate example methods for implanting a
subject-specific patterned balloon device.
[0064] FIGS. 22A-22D illustrate example methods for implanting a
subject-specific patterned balloon device.
[0065] FIG. 23 illustrates a flowchart of a method for fabricating
an implantable balloon device.
[0066] FIGS. 24A-24F show stages of construction of an implantable
balloon device according to the method of FIG. 23.
[0067] FIG. 25 depicts a schematic representation of two methods
for constructing low-volume thin soft robotic devices.
Thermobonding method is shown on the left. Laser welding method is
shown on the right.
[0068] FIGS. 26A-26D show different conformations of two soft
robotic devices. FIG. 26A shows an unactuated bending soft robotic
device with a flat geometry. FIG. 26B shows an actuated bending
soft robotic device with a flat geometry. FIG. 26C shows an
unactuated soft robotic device with complex geometry. FIG. 26D
shows an actuated soft robotic device with complex geometry.
[0069] FIG. 27 depicts three conformations of a heart valve
embodiment of a soft robotic device: a rolled up, low-volume
conformation on the left; an unactuated conformation in center; and
an actuated conformation on the right.
[0070] FIGS. 28A-28C depict a schematic representation of the
fabrication process using a laser welding method. In FIG. 28A,
layers of thermoplastic polyurethane are laminated using a heat
press. FIG. 28B shows a laser beam cutting/welding the laminated
layers to a desired pattern. FIG. 28C shows the inflated chamber
bounded by layers 1 and 3 disposed on each side; the asymmetry of
the layer stiffness leads to a bending motion.
[0071] FIGS. 29A-29C elaborate on the bending motion of a soft
robotic device. FIG. 29A depicts a sequence of images showing the
bending motion of a soft robotic device of type I. FIG. 29B shows a
heat-map of maximum principle strain in different portions of the
bending device while in ultimate bent configuration. FIG. 29C shows
a comparison between the simulated and experimental lateral
displacements of a thin soft robotic device using FEM
simulation.
[0072] FIGS. 30A-30D depict a soft robotic device of type II. FIG.
30A shows an asymmetric 2D profile for a soft robotic device of
type II. FIG. 30B depicts a sequence of images showing the bending
motion of soft robotic device of type II. FIG. 30C shows a
comparison of the ultimate bending configuration of the soft
robotic device with that of FEM simulation. FIG. 30D shows a
comparison between simulated and experimental lateral displacements
of the thin soft robotic device.
[0073] FIGS. 31A-31C depict a schematics and prototypes of two soft
robotic devices. FIG. 31A shows a rotary soft robotic device with a
300.degree. rotation capability. FIG. 31B shows a axial soft
robotic device. FIG. 31C a biaxial soft robotic device in an
unactuated and an actuated conformations.
[0074] FIGS. 32A-32C show a bi-directional soft robotic device.
FIG. 32A depicts a schematic of a bi-directional soft robotic
device and design of its working principle. FIG. 32B shows images
of the unactuated, open, and closed conformations for this thin
soft robotic device. FIG. 32C depicts how these different
conformations grasp objects for the pick and place task.
[0075] FIGS. 33A-33D depict a schematic design of a water strider
soft robotic device for generating forward in FIG. 33A and backward
in FIG. 33B swimming motions. Unactuated and actuated conformations
in forward motion mode are shown in FIG. 9C and FIG. 33D,
respectively.
[0076] FIGS. 34A-34D depict a water strider soft robotic device.
FIG. 34A shows a sequence of swimming motion for one cycle. FIG.
34B depicts the pressure inside the soft robotic device during the
inflation and deflation periods. FIG. 34C shows the horizontal
displacement of the soft robotic device during the inflation and
deflation phases. FIG. 34D shows the total displacement after 7
cycles (14 sec).
[0077] FIG. 35 shows a comparison between the bourdon tube and the
soft thin rotary soft robotic devices.
[0078] FIG. 36 shows a mean burst pressure of the balloon as a
function of speed and power. The red dotted line refers to the
maximum burst pressure of 10.5 psi achieved for all conditions.
[0079] FIGS. 37A and 37B show a 6 DOF ABB (IRB120) robot arm, 3D
printed adaptor and a soft robotic bidirectional gripper.
[0080] FIG. 38 depicts an actuation system of the Water Strider
Robot device.
[0081] FIG. 39 shows the bending displacement of a soft robotic
device of type I under different pressure inputs.
[0082] FIG. 40 shows the bending displacement of a soft robotic
device of type II under different pressure inputs.
[0083] FIG. 41 shows a twisting angle of a rotary soft robotic
device for different input pressures.
[0084] FIGS. 42A-42C show a heart valve embodiment of a soft
robotic device. FIG. 18 A shows several depictions of a heart valve
in actuated and unactuated conformations. FIG. 42B depicts change
in pressure over time as the heart valve is opened and closed. FIG.
42C shows changes in pressure as flow rate increases.
[0085] FIGS. 43A-43E depict a thermoplastic bonding method that can
be used to integrate multiple layers and a frame of a soft robotic
device at a single step.
[0086] FIGS. 44A-44D show an inflatable polyurethane stent in its
low-volume conformation in FIG. 44A, deflated conformation in FIG.
44B, inflated conformation in FIG. 44C and inflated conformation
connected to an inflating source in FIG. 44D.
[0087] FIGS. 45A-45F show an embodiment in which the soft robotic
device is a stent. FIG. 45A shows a honeycomb pattern on a flat
plain balloon. FIG. 21 B shows a patterned balloon, which can be
bent to from a stent. FIG. 45C shows a soft stent in its low-volume
conformation. FIG. 45D shows a stent in its deflated conformation.
FIG. 45E shows a stent in its inflated conformation connected to an
inflation source. FIG. 45F shows a stent in its inflated
conformation.
[0088] FIGS. 46A and 46B show an embodiment, in which the soft
robotic device is a stent. The stent can be attached to a hanging
mechanism as illustrated in FIG. 46A. The stent can be further
inflated inside a pig's aorta while the aorta is attached to
various weights as illustrated in FIG. 46B, showing the strength of
the stent.
[0089] FIGS. 47A-47D show additional images showing different views
of the stent as well as the sizes and burst pressures for different
patterns.
[0090] FIGS. 48A-48D show views of different patterns for the
stent.
[0091] FIGS. 49A-49D show views of different patterns for the
stent.
[0092] FIG. 50A shows a set of realistic annulus shapes. FIG. 50B
shows a graph depicting the maximum pull-out for a stent vs.
applied pressure.
[0093] FIGS. 51A-51F show a series of graphs depicting pressure vs.
time.
[0094] FIG. 52 shows two objects coupled together.
DETAILED DESCRIPTION
[0095] For purposes of reading the description of the various
implementations below, the following descriptions of the sections
of the specification and their respective contents may be
helpful:
[0096] Section A describes techniques for micropatterning
arbitrarily shaped three-dimensional (3D) objects;
[0097] Section B describes micropatterned implantable balloons;
and
[0098] Section C describes thin inflatable actuators.
A. Micropatterning 3D Objects
[0099] Micro- and/or Nano-patterning of surfaces can be a powerful
technique for engineering the surface properties of devices or
objects without changing their underlying chemistry, functionality,
and bulk properties. These techniques allow engineering of surface
properties, such as adhesion, wettability, and optical properties,
and can be used to regulate cell behavior. While there are a myriad
of approaches to fabricate micro-patterned surfaces, such as using
self-assembly, electrostatic forces, phase shift lithography, and
other phenomena, these methods are typically limited to specific
types of patterns and planar substrates, and are often costly and
time-consuming
[0100] Some soft lithographic techniques can allow for the transfer
of micro-patterns from 2D prefabricated templates to objects of
interest. For example, a pattern can be molded onto a flexible
stamp, which can conform to the surface of an object. Then the
transfer can be accomplished by solvent-assisted embossing, hot
embossing, or imprint lithography. These approaches can benefit
from the high resolution of 2D microfabrication, but can only be
used on small radius of curvature substrates or objects with
individual bends. Therefore, more recently flexible phase shift
masks evolved as a powerful tool for patterning of photopolymers on
complex surfaces. A significant amount of work has been devoted to
advancing the type and complexity of features that can be
transferred by these techniques. However, less effort has been
focused on expanding the type and complexity of objects that can be
patterned, and the ease and cost effectiveness of patterning.
[0101] There are several challenges that must be addressed to apply
soft lithographic approaches to more complex objects. For example,
the stamp must be able to conform to a complex shape without
dramatically stretching or folding, the stamp must be applied
uniformly to the surface of the object with equal pressure without
inducing stamp deformation or stamp collapse, and the stamp must
contact the object without inducing air bubbles or other defects.
To address these three challenges, this disclosure provides a
variety of techniques, such as vacuum bagging, which was originally
developed for lamination of fabrics, resins, and fabric/resin
composite materials into complex 3D geometries. In general, vacuum
bagging applies a uniform pressure on an object by inducing a
differential pressure between the inside and outside of a bag made
from thin and conformable films. Although this technology has
matured extensively in large manufacturing, its use for
micro-fabrication has not been explored in depth prior to this
disclosure.
[0102] One aspect of this disclosure relates to a novel approach
that relies on ultra-thin conformable micro-patterned stamps in
conjunction with vacuum bagging. This technique can be referred to
herein as conformal template vacuum bagging (CTVB). The flexibility
of the stamps can be combined with various advantages of the vacuum
bagging process, including uniform pressure distributions along the
object surface, inert reaction environments while embossing, and
the ability to infuse resins into gas-free templates, thus
preventing air bubbles or defects. These features address some key
technical challenges of surface micropatterning of complex 3D
objects. Furthermore, because vacuum bagging is a robust,
inexpensive, and well-established technology, this method can be
applied simply with inexpensive equipment and is easily scalable
for manufacturing. Finally, because the vacuum bag can conform to
almost any geometry, the method does not require the operator to
know the object geometry in advance, dramatically improving the
versatility and ease of use.
[0103] The techniques described in this disclosure can have
application in the field of medical implants and devices, as
described further below in connection with Section B. The
techniques have been demonstrated for a variety of materials common
to the medical device industry due to their mechanical properties
and biocompatibility, namely silicone, nitinol alloy, and
polyurethanes (Tecoflex.TM. polyurethane, and ChronoFlex.RTM.
polycarbonate-urethane). Polyurethanes can have a wide range of
mechanical properties (elongation at break, shore hardness, and
ultimate strength) that are useful for engineering composite
implants. In some implementations, patterns can be hexagonal
surface micro-patterns inspired by tree frogs and sharkskin
riblets, which have been shown to enhance wet friction, and to
decrease interfacial shear stresses, respectively. These patterns
can have great potential to medical device applications, but are
also easily applied to any 2D surface micropattern. To illustrate
the versatility of this method, a variety of objects were selected
and patterned, as described further below. For example, this
disclosure provides example of micropatterned 3D objects including
a 3D printed chess piece, a super-elastic nitinol guidewire after
heat treatment, a Foley catheter, and a soft robotic star shaped
gripper made from silicone. This disclosure also describes several
variants of this approach to generate surface patterns through
resin infusion or thermoforming/embossing. These techniques allow
for a cost-effective integration of rapid prototyping with
lithography for a variety of materials and objects.
[0104] FIGS. 1A-1D show stages of construction of a general process
for patterning a 3D object. As shown in FIG. 1A, a 2D master
template 105 can be fabricated, for example, via conventional
photolithography. The master template 105 can be used to mold a
soft flexible template 110. A 3D object 115 can be wrapped in the
flexible template 110, as shown in FIG. 1B. The 3D object 115 and
the flexible template 110, along with a breather film 120, can be
placed in the vacuum bag 125 as shown in FIG. 1C. The breather film
120 can be a thin porous media for distribution of vacuum within
the bag 125. As shown in FIG. 1D, vacuum can be applied to remove
air from the vacuum bag 125. The vacuum bag 125 containing the
assembly can be placed inside an oven to emboss the pattern on the
3D object 115.
[0105] FIG. 2 illustrates a flowchart of a method 200 for
micropatterning a 3D object. FIGS. 3A-3H show stages of
construction of a micropatterned 3D object according to the method
of FIG. 2. FIGS. 2 and 3A-3H are discussed together below.
[0106] Referring now to FIG. 2, the method 200 can include
providing a 3D object (stage 205). The 3D object can be any type of
object whose surface is to be patterned. In some implementations,
the 3D object can have a complex shape. For example, the 3D object
may have one or more surfaces having curves, folds, angles,
creases, or other features. In some implementations, the 3D object
can be a medical device, such as an implantable device. The 3D
object can be formed, for example, from a biocompatible or
hemocompatible material, such as silicone. The 3D object can be
fabricated from a variety of materials using a variety of
manufacturing techniques. In some implementations, 3D object can be
printed using an additive manufacturing technique (e.g., 3D
printing). For example, the 3D object can be printed using rigid
materials such as VeroClear along with a 3D printer such as an
Objet Connex 260 printer. After printing, the rigid material may
also be boiled (e.g., in water for 90-150 minutes) and dried.
[0107] The method 200 includes micropatterning a rigid material
(stage 210). In some implementations, the rigid material can be a
material capable of being patterned via photolithography, such as
silicon. For example, conventional photolithography on a hard
substrate, such as a silicon wafer, can be performed. In some
implementations, the rigid material can include a 4-inch silicon
wafer. As shown in FIG. 3A, a silicon wafer 305 can be coated with
a photoresist material 310. For example, the photoresist material
310 can be applied to the silicon wafer 305 via a spin coating
process. In some implementations, the photoresist material 310 can
be SU-8 2 or SU-8 2025. A lithographic process can be applied to
pattern the photoresist material 310, as illustrated in FIG. 3B.
For example, the photoresist material 310 can be selectively
exposed to UV radiation according to the selected pattern. The
pattern formed in the photoresist material 310 can be selected for
its ability to enhance one or more surface characteristics of a 3D
object to which the pattern is to be applied. For example, the
pattern can be a pattern selected to improve an optical
characteristic, a friction characteristic, an adhesion
characteristic, a biocompatibility characteristic, or any other
surface characteristic or combination of surface characteristics of
the object. The pattern can include sidewalls and or channels that
may be straight, curved, or angled. In some implementations, the
pattern can be a regular repeating (e.g., periodic) pattern. The
pattern can have a thickness of between 1 micron and 40 microns.
For example, the pattern can have a thickness of 1 micron, 2
microns, 3 microns, 4, microns, 5 microns, 6 microns, 7 microns, 8
microns, 9 microns, 10 microns, 15 microns, 20 microns, 25 microns,
30 microns, 35 microns, 38 microns, 40 microns, 45 microns, 50
microns, 60 microns, 70 microns, 80 microns, 90 microns or 100
microns. In some implementations, the pattern can have a thickness
of greater than 100 microns. In some implementations, the
photoresist material 310 can be hard baked in a convection oven at
a temperature in the range of 150 degrees C. to 250 degrees C.
after it has been patterned. In some embodiments, the temperature
can be 100 degrees C., 110 degrees C., 120 degrees C., 130 degrees
C., 140 degrees C., 150 degrees C., 160 degrees C., 170 degrees C.,
180 degrees C., 190 degrees C., 200 degrees C., 210 degrees C., 220
degrees C., 230 degrees C., 240 degrees C., 250 degrees C., 275
degrees C., 300 degrees C., 325 degrees C., 350 degrees C., 400
degrees C., 450 degrees C., 500 degrees C., or greater.
[0108] The method 200 can include fabricating a flexible stamp
(stage 215). In some implementations, the rigid material
micropatterned in stage 210 can serve as a master template, and can
be used to create the flexible stamp. For example, the
micropatterned rigid material can serve as a reusable master
template that can be used to fabricate any number of flexible
stamps. In some implementations, a flexible stamp can be molded
using the master template. For example, as shown in FIG. 3C, an
elastomeric material 315 can be coated over the photoresist
material 310 and the silicon wafer 305, (e.g., via a spin coating
process). In some implementations, the elastomeric material 315 can
be a silicone material, PDMS, or any other flexible elastomeric
material capable of being molded to take on the shape of the
patterned photoresist material 310. For example, the elastomeric
material can be ELASTOSIL.RTM. M4601. In some implementations, the
elastomeric material 315 can be cured, for example by exposure to
ultraviolet light, to solidify the elastomeric material 315. As
shown in FIG. 3D, after curing, the solidified elastomeric material
315 can be peeled off of the photoresist material 310 and the
silicon wafer 305, thereby forming the flexible stamp 320.
[0109] In some other implementations, a soft inversion of the hard
master template (e.g., the silicon wafer 305 and the patterned
photoresist material 310) can be formed. For example, the hard
master template can be cast with silicone (e.g., Sylgard 184),
which can be cured by exposure to heat (e.g., temperature in the
range of 80 degrees C. to 120 degrees C.) for curing and then
peeled off of the master template. In some implementations, such a
silicone soft template can also be surface treated. For example, a
self-assembled monolayer treatment can be applied (e.g., trichloro
perfluoro silane) to a surface of the soft template to maximize the
surface energy of the soft template. The silicone soft template can
then be spin coated with the elastomeric material to form the
flexible stamp 320.
[0110] In some implementations, the flexible stamp 320 can undergo
a surface treatment process. For example, the flexible stamp 320
can be fluorinated, as shown in FIG. 3E. In some implementations,
the surface treatment can include applying trichloro perfluoro
silane to the flexible stamp 320. The surface treatment applied to
the flexible stamp 320 can be selected to alter (e.g., decrease or
increase) its adhesion to the 3D object to be patterned in a
subsequent stage of the method 200. For example, in some
implementations, the flexible stamp 320 can be functionalized via a
self-assembled monolayer treatment to decrease its adhesion. In
some implementations, a surface of the 3D object to be patterned
also can undergo a surface treatment, such as a coating applied to
at least a portion of its surface. For example, in some
implementations the 3D object can be dipped into a material such as
polyurethane or another polymer film to produce a thin polymer film
on the surface of the 3D object. In some implementations, the
material used to coat the 3D object can be selected to be
biocompatible, for example to facilitate its use in medical devices
such as implants for human subjects.
[0111] The method 200 can include wrapping the 3D object in the
flexible stamp (stage 220) and inserting the 3D object wrapped in
the flexible stamp into a vacuum bag, along with a breather film
(stage 225). The results of this are illustrated in FIG. 3F. As
shown, the 3D object 330 has been coated with a film 335 (e.g., a
polymer film). The patterned side of the flexible stamp 320 is
wrapped around the coated 3D object 330. The 3D object 330 wrapped
in the flexible stamp 320 is place inside a vacuum bag 340. In some
implementations, the vacuum bag 340 can be formed from a nylon
material. In some implementations, the vacuum bag 340 can be
assembled using a bagging film such as Stretchlon.RTM. 300 and 800,
along with one or more sealant tapes, such as ACP composites.
[0112] As also depicted in FIG. 3F, the method 200 can include
applying vacuum to the 3D object and the flexible stamp within the
vacuum bag (stage 230). Although not depicted in FIG. 3F, in some
implementations a breather film can also be positioned between at
least a portion of the flexible stamp 320 and the vacuum bag 340
when vacuum is applied. For example, the breather film can be a
porous, flexible material that can help to ensure even distribution
of vacuum within the vacuum bag 340. In some implementations, the
breather film can include Airtech's Airweave.RTM. material. One or
more quick release vacuum connectors along with one or more vacuum
pumps can be used to apply and control vacuum within the vacuum bag
340. As a result of applying vacuum within the vacuum bag 340, the
greater air pressure outside the vacuum bag 340 causes the vacuum
bag 340 to press inward against the flexible stamp 320, which in
turn causes the patterned side of the flexible stamp 320 to be
pressed against the coated surface of the 3D object 330.
[0113] The method 200 can also include applying heat to the 3D
object and the flexible stamp within the vacuum bag (stage 235).
Heat can be applied while vacuum is also applied. In some
implementations, heat can be applied by putting the vacuum bag 340
into an oven. As a result, the coating 335 applied to the surface
of the 3D object 330 (or, in some implementations, the uncoated
surface of the 3D object 330 itself) can soften, thereby allowing
the pressure from the vacuum bag 340 to press the patterned side of
the flexible stamp 320 into the coating 335 on the 3D object 330
via thermoplastic forming. This can also be referred to as hot
embossing. In some implementations, the method 200 can include
cooling the entire assembly, to allow the coating 335 to set with
the pattern of the flexible stamp 320 imprinted on it. The 3D
object 330 coated with the coating 335 and the flexible stamp 320
can then be removed from the vacuum bag 340, and the flexible stamp
320 can be peeled off. The result is the 3D object 330 coated with
the coating 335 having a surface pattern corresponding to the
pattern of the flexible stamp 320, as illustrated in FIG. 3H. It
should also be understood that, in some implementations, the
pattern can be formed directly into the surface of the 3D object
330 itself, rather than into the coating 335 that has been applied
to the 3D object 330.
[0114] In general, the method 200 can be used to micropattern a
variety of types of 3D objects, and many variations (e.g., types of
materials, surface treatments, etc.) can be used in connection with
the method 200. For example, results of the method 200 were
confirmed experimentally for several different objects and
micropatterns, as described further below. In particular, using
variations of the method 200, micropatterns inspired by tree frogs
(e.g., periodic hexagonal micropatterns) and shark skin riblets
were applied to objects including a 3D printed chess piece, a Foley
catheter, a nitinol guidewire, and a star-shaped gripper.
[0115] The chess piece was 3D printed in VeroClear material using
an Objet Connex 260 printer, boiled in water for 2 hours dried, and
dip-coated in polyurethane (e.g., 13 wt % Tecoflex SG-60D in
Dimethylacetamide (DMAC), cured overnight at 80.degree. C.).
Sufficient adhesion was observed between the 3D printed part (e.g.,
the VeroClear material) and Tecoflex such that no delamination was
observed at any stage of vacuum bagging or subsequently. The 20 Fr
silicone Foley catheter (provided by Bard Medical) was plasma
treated (e.g., air plasma). The catheter was also soaked in 12 vol
% 3-glycidoxypropyltrimethoxysilane in ethanol for two hours, and
dip-coated with Tecoflex. In some implementations, this treatment
can create a surface monolayer on silicone that facilitates
covalent bonding with polyurethane for enhanced adhesion. A nitinol
guidewire having a 380 micron diameter with a light oxide finish
and annealed straight (provided by Fort Wayne Metals) was heat
treated to form the curved structure (e.g., wrapped around a
mandrel at 500.degree. C. for 5 minutes and then quenched). No
additional adhesion promoter was used, and no delamination was
observed after vacuum bagging. The star-shaped gripper was cast
from silicone (e.g., Ecoflex 00-30) and nylon mesh. The gripper
molds were 3D printed from VeroClear material using an Objet Connex
260 printer. The molds were boiled in water for two hours and
cooled to reduce effects of surface cure inhibition. Subsequently,
the top part and bottom part of the gripper were cast in silicone
(e.g., Ecoflex 00-30). The parts were cured at room temperature for
1 hour. Fresh silicone (e.g., Ecoflex 00-30) was mixed and applied
to the surfaces, and nylon fabric was sandwiched between the
parts.
[0116] Thus, various grades of Chronoflex and Tecoflex with
different mechanical properties were prepared for use with the
method 200, to illustrate the versatility of the method 200 and to
accommodate the varying mechanical properties of the objects coated
with these materials. In some implementations, coating different
objects with polyurethane can be achieved by dip coating the
objects in solutions of polyurethane dissolved in DMAC. A
ChronoFlex/DMAC solution can be provided by the manufacturer and
diluted 50%, by volume, in DMAC before dipping. Tecoflex can be
provided by the manufacturer in the form of pellets, which can be
dissolved in DMAC with different ratios. In some implementations,
the ratios can be selected such that relatively high concentrations
of polyurethane could be achieved. Polyurethanes for use in the
method 200 can be mixed using a planetary/centrifugal mixer (e.g.,
a Thinky SR-500 mixer) for 60 minutes at 2200 rpm.
[0117] FIG. 4 shows a magnified view 400 of a hexagonal
micropattern that can be formed on the surface of a 3D object using
the method 200 of FIG. 2. The micropattern shown in FIG. 4 is
inspired by tree frogs, and can be used to enhance wet adhesion. In
some implementations, this pattern can be applied to medical
devices (e.g., vascular devices) to help them remain in place
inside a subject. FIG. 5 is a graph 500 showing coefficients of
friction for each of four variations of the hexagonal pattern shown
in FIG. 4, labeled A-D in FIG. 5. Design parameters and other
characteristics for each of these variations are provided in Table
1 below:
TABLE-US-00001 TABLE 1 Channel Exposure Pattern Depth Periodicity
Width Time Type (.mu.m) (.mu.m) (.mu.m) (mJ/cm.sup.-2) Photoresist
A 3.6 300 30 .+-. 2 4 .times. 5 SU8 2 B 3.6 300 28 .+-. 2 8 .times.
5 SU8 2 D 5.5 300 34 .+-. 2 7 .times. 5 SU8 2025 D 36 300 37 .+-. 2
10 .times. 5 SU8 2025
[0118] In Table 1, the values are based on 2D templates that were
used for transferring patterns. Depths are measured using a
profilometer and optical microscopes. Periodicity is measured along
the [110] direction using optical microscopy. Channel width is
defined and measured on the top side of the patterns using optical
microscopes.
[0119] By controlling the thickness, exposure, and development
conditions of the 2D template, micro patterned films with the same
lattice, but different feature heights and widths (e.g., those of
patterns labeled A, B, C, and D in FIG. 5) were fabricated. For all
films, some degree of feature undercut was obtained, which may
improve wet friction. Films A and B had the same height, but film B
had features with smaller channel width (e.g., due to a longer
exposure time). Films C and D had film thicknesses greater than A
and B. Thus, comparing patterns A and B shows the significance of
the in-plane-geometry of the channels and comparing B and C shows
the significance of feature height. Wet dynamic and static
coefficients of friction for each film were normalized to those of
un-patterned films. The comparison presented in FIG. 5 shows
enhancement in coefficients of friction up to three times that of
un-patterned films. Comparison of films shows that channel depth
can affect wet friction. The overall enhancement of wet friction
associated with these tree frog inspired micropatterns can make
them useful for micropatterning of nonplanar medical devices due to
the frequent requirement to adhere to or anchor against tissue in a
wet environment.
[0120] FIG. 6 illustrates various views 600 showing different
magnifications of a hexagonal micropattern applied to a 3D printed
chess piece 605. FIG. 6 shows the versatility of the method 200,
which was used to transfer the hexagonal pattern to the chess piece
605. For example, despite the complicated geometry of the chess
piece 605, the pattern was transferred over the area of the object
even in the dimples, creases, and folds of the object. It should be
noted that additive manufacturing is useful for fabrication of
nonplanar objects with arbitrary and complex shape, such as the
chess piece 605. However, the ability to produce fine micro-scale
features via additive manufacturing is limited. The features of the
micropattern illustrated in FIG. 6 are thinner (e.g., about 30
.mu.m) than those that can typically be resolved by 3D printers,
and micropatterns with far smaller features can easily be formed by
the method 200. For example, feature sizes may be less than about
20 microns, less than about 10 microns, or less than about 5
microns. In some implementations, feature sizes of around 3 microns
may be obtained using the method 200. Thus, by utilizing 3D
printing (e.g., to manufacture an object to be patterned, such as
the chess piece 605) in concert with the micropatterning technique
of the method 200, tremendous design freedom exists. Accordingly,
using the method 200 can allow for a combination of the advantages
of additive manufacturing for rapid prototyping of complicated
surfaces with the advantages of lithography for micro-scale
features.
[0121] In some implementations, the sharpness of the patterns may
be reduced where the radius of curvature of the 3D object being
patterned is very small, as illustrated in FIG. 6. This effect can
be understood based upon the kinematics of the deformation of the
flexible stamps, with a thickness of (t) bending along a surface
with a small radius of curvature (r). Assuming the neutral plane
occurs in the mid-plane of the stamp, the kinematic relationship in
the theory of plates dictates that e1=t/2r. Where e1 is the normal
in-plane strain on the surface of the stamp in contact with the
object. A large in-plane strain can result in a large normal strain
in the stamp, perpendicular to the stamp surface, e3=-n e1, where n
is the poisons ratio, .about.0.5 for silicones. As a result, there
is a reduction of the depth of pattern at curved areas is
proportional to t/r. In the example of FIG. 6, t can be
approximately 200 microns, which can explain why in the areas that
the radius of curvature is on the same order, a reduction in
pattern sharpness can be observed. Furthermore, this suggests that
that micropatterning on larger curvature surfaces may benefit from
thinner stamps. However, it should be understood that the thickness
of a flexible stamp can be greater than or less than 200 microns.
For example, a flexible stamp can have a thickness of less than 20
microns, less than 30 microns, less than 40 microns, less than 50
microns, less than 60 microns, less than 70 microns, less than 80
microns, less than 90 microns, less than 100 microns, less than 150
microns, less than 175 microns, less than 200 microns, less than
225 microns, less than 250 microns, less than 275 microns, less
than 300 microns, less than 350 microns, less than 400 microns,
less than 450 microns, or less than 500 microns. In some
implementations, a flexible stamp can have a thickness of greater
than 500 microns.
[0122] FIG. 7 illustrates various views of a micropattern applied
to a high aspect ratio wire 705. Nitinol frames, stents and
guidewires can provide structural elements associated with a wide
variety of medical devices. Thus, FIG. 7 illustrates the ability of
the method 200 to produce high quality micropatterning of such
small, high aspect ratio elements. In the example of FIG. 7, the
wire 705 was formed and annealed in a curved shape. FIG. 7 shows
the wire 705 protruding from a lumen 710 and micropatterned with a
pattern inspired by shark skin riblets, which can help to reduce
fluid shear forces. The wire 705 was coated with polyurethane
(e.g., TecoFlex MG-8020, having a high flexural modulus of about
165,000 psi) to demonstrate the ability of the method 200 to apply
a micropattern to stiffer materials. Unlike alternative methods,
where wires or sheets of nitinol are patterned prior to forming,
patterns can be imparted after annealing the nitinol in the desired
shape due to the versatility of the method 200. In some
implementations, this versatility can be a requirement to apply
surface micropatterns to existing nitinol devices. Polyurethanes,
similar to those used in this example, may enhance the
thrombogenicity of nitinol when used as a passivation layer.
Moreover, the shark-skin inspired riblets of the micropattern shown
in FIG. 7 are known for reduction of drag forces and fluid shear
stresses.
[0123] FIG. 8 illustrates a view 800 of a micropattern applied to a
high aspect ratio wire 805. The wire 805 is similar to the wire 705
of FIG. 7. However the micropattern applied to the wire 805 is a
hexagonal pattern inspired by tree frogs. In some implementations,
such a pattern can help to enhance anchoring of stents or other
implantable devices against tissue structures. The wire 805 was
patterned according to the method 200, described above in
connection with FIG. 2. As shown, the pattern is reliably
transferred to the wire 805 via the method 200. In some
implementations, the pattern shown in FIG. 8 can be used to
engineer characteristics such as thrombogenicity, hemodynamics, and
friction/adhesion. Accordingly, the method 200 can provide a new
route for engineering of these properties in existing nitinol
stents, devices, and other implants.
[0124] FIGS. 9A-9C show various views of a micropatterned Foley
catheter 900. The Foley catheter 900 is typically used to drain
urine from the bladder. FIGS. 9A-9C show the Foley catheter 900 in
at various degrees of magnification as labeled in the figures, as
well as in both an inflated state (e.g., FIGS. 9A and 9B) and an
uninflated state (FIG. 9C). A hexagonal micropattern inspired by
tree frogs was applied to the Foley catheter 900 using the method
200 of FIG. 2. In some implementations, this pattern can help to
increase wet friction on the balloon, to enhance anchoring the
catheter 900 in the bladder. Furthermore, this example illustrates
the compatibility of the method 200 with soft materials. In this
example, a highly extensible polyurethane (Tecoflex-SG80A with
ultimate elongation of about 660%) is used to match the elastic
properties of silicone. Due to the highly extensible nature of the
micro-patterned polyurethane films, the catheter 900 remains highly
stretchable and functional upon inflation (see FIG. 9A), with the
micropattern intact (see FIG. 9B). Upon deflation, the catheter
retains its original cylindrical shape (see FIG. 9C), with the
patterns still clearly visible. In some implementations,
micropatterning of the entire balloon area of the catheter 900 can
be achieved in a single step (e.g., a single instance of the method
200), making it cost effective and scalable for enhancement of
existing medical devices.
[0125] In some implementations, fields such as soft robotics can
employ the cost-effective techniques of 3D printing and silicone
molding for fabrication of grippers, end effectors, and more
complex machines. While complicated geometries for grippers can be
fabricated rapidly, they lack surface micro-features that could
enhance their functionality. For this reason and the concepts
discussed previously, the method 200 can be well suited to enhance
the properties of such devices. FIG. 10 shows various views 1000 of
a micropatterned inflatable star-shaped gripper made from silicone.
In this example, the tree frog inspired hexagonal pattern was used,
which can enhance the gripper's functionality, for example, by
increasing friction. In some implementations, such a pattern can be
useful for applications in which the gripper holds wet objects. It
should also be understood that other features such as Gecko
inspired patterns could be incorporated for improving dry
frictional properties, and could be applied to the surface of the
gripper (or other 3D object) using the method 200.
[0126] In order to estimate the expected change in the periodicity
of patterns applied using the method 200, images of the
micropatterned star shape gripper and wires were analyzed.
Variations of between approximately 3% and 9% were observed. These
changes are mainly due to handling, stamp mechanics, and the
process of thermoplastic embossing. In order to further elucidate
the fidelity of the patterns transferred via the method 200, beyond
the fundamental limits, the tree frog inspired hexagonal patterns
(i.e., Pattern C in Table 1 above) was transferred from 2D
templates to flat silicon wafers coated with polyurethane
(MG-8020). The depth, periodicity, and width of the patterns were
characterized using a profilometer (Bruker, Dektak-XT) and optical
microscopy. The comparison between the patterns transferred showed
less than a 10% reduction in the depth of the pattern (e.g., 5.5 to
5 microns), less than 4% change in periodicity along random
directions, and no more than 5% change in the width of the
patterns.
[0127] Thus, the techniques described herein, such as the method
200, represent cost-effective techniques for micro-patterning
arbitrary 3D objects, with an emphasis on medical applications.
These techniques combines several technologies, including
photolithography, soft lithography, and vacuum bagging. In some
implementations, these techniques can be integrated with current 3D
printing technologies for rapid prototyping of different devices,
and can be scalable for medium or large batch production.
Furthermore, because these techniques can be used to pattern
objects of arbitrary geometry, they can be used to modify or
enhance the properties of many existing objects and devices.
[0128] FIGS. 11A-11C show stages of a process for resin infusion on
a 3D object. As illustrate in FIG. 11A, breathers 1105 are
positioned to overlap with fabric 1110 (e.g., Kevlar) and a resin
infusion mesh 1115. The fabric 1110 is laminated on a 3D object and
then sealed in a vacuum bagging film 1120. As shown in FIG. 11B,
vacuum sealing tape 1130 can be used to seal the vacuum bagging
film 1120. A tube 1125 is connected to the breathers 1105. Another
tube 1135 is connected to the resin infusion mesh 1115. Each of the
tubes 1125 and 1130 can be opened and shut off using hose
clamps.
[0129] First, the vacuum bag is vacuumed via the tube 1125 while
the resin infusion tube 1135 is closed, as shown in FIG. 11C. In
some implementations, thermoset biopolymer can be mixed and
degassed, and then the resin infusion tube 1135 can be placed in
the resin infusion mesh 1115 and a hose clamp can be opened.
Consequently, resin can be infused in the vacuum bag 1120 through
the vacuumed pores of the fabric 1110. Upon completion of infusion
in the fabric 1110, both tubes 1125 and 1135 can be shut off and
the vacuum bag 1120 can be placed in an oven for curing. Finally,
the fabric 1110 and the resin infusion mesh 1115 can be cured with
the shape of the 3D object on which they were laminated.
[0130] FIG. 12A illustrates a setup 1200 that can be used for resin
infusion and micropatterning of a 3D object formed from PDMS. The
setup 1200 combines the principles of the method 200 for imprinting
a micropattern on a 3D object, along with principles of the resin
infusion process of FIGS. 11A-11C. In the setup 1200, ultrathin
glass tissue is laminated onto an object formed from PDMS, and a
micropatterned template (e.g., a flexible stamp as described above
in connection with the method 200) is wrapped around the PDMS
object. The glass tissue can be a porous film made from glass
fibers. In some implementations, the PDMS object and the glass
tissue can be plasma treated to result in formation of covalent
bonds after curing the resin. The PDMS object wrapped in the
flexible stamp (labeled 1205 in FIG. 12A) is inserted into a vacuum
bag 1210. Vacuum is applied within the vacuum bag 1210 via a tube
1215, and resin is infused into the vacuum bag 1210 via a tube 1220
in a manner similar to that described above in connection with
FIGS. 11A-11C. As a result, resins are passed through pores in the
flexible stamp and the glass tissue, thereby forming a pattern 1250
on the surface of the PDMS object as shown in FIG. 12B. In this
example, the pattern 1250 is the tree from inspired hexagonal
pattern, however any arbitrary pattern can be applied using this
technique.
[0131] FIGS. 13A and 13B show a comparison between micropatterns
formed via 3D printing and conformal template vacuum bagging. FIG.
13A illustrates a magnified image of a 3D printed part 1305. The 3D
printed part 1305 was fabricated using a CAD file that included a
hexagonal pattern having hexagons of approximately 500 microns in
width on its surface. However, as shown, despite the inclusion of
the pattern in the file used to print the part 1305, the surface of
the part 1305 does not exhibit any observable hexagon pattern. This
can be due to limitations in the resolution of typical 3D printing
devices, for example. In contrast, FIG. 13B shows a part 1310 that
was patterned according to the conformal template vacuum bagging
technique described in connection with the method 200 of FIG. 2.
The flexible stamp used to fabricate the part 1310 had a pattern
having hexagons of approximately 500 microns in width, similar to
the pattern that was incorporated into the file used to fabricate
the part 1305. However, the pattern is more reliably transferred
and is easily visible on the part 1310, due to the superiority of
the vacuum bagging technique as compared to 3D printing.
[0132] FIG. 14 illustrates a setup 1400 demonstrating the
scalability of vacuum bagging for patterning 3D objects. The setup
1400 and its principles of operation are similar to that described
above in connection with the method 200 of FIG. 2. However, six
micropatterned templates each wrapped around a respective 3D object
(labeled 1405a-1405f in FIG. 14) are place inside a single vacuum
bag 1410. Vacuum can be applied to the objects 1405a-1405f
simultaneously, and the entire assembly can be put into an oven at
once. In some implementations, any arbitrary number of 3D objects
wrapped in a respective template could be inserted into a single
vacuum bag similar to the vacuum bat 1410. Thus, the setup 1400
demonstrates that the method 200 can be scalable for patterning
multiple objects simultaneously. It should also be understood that
the objects 1405a-1405f need not have the same shape as one
another, and that the patterns applied to each need not be the
same, as the principles of operation are not dependent on the
particular geometry of the objects or the patterns of the
templates.
[0133] FIG. 15 shows a nonplanar object 1500 at various levels of
magnification. In some implementations, the object 1500 can be
formed from silicone in any arbitrary, nonplanar shape. The object
1500 can be coated on its surface with a polyurethane material,
such as ChronoFlex. The object 1500 can then be patterned according
to the method 200 of FIG. 2, as shown as the higher levels of
magnification in FIG. 15. Such an object can be useful for medical
applications, such as implantable devices, because silicone is a
biocompatible material while ChronoFlex also features excellent
hemocompatibility and biocompatibility. Thus, the object 1500 could
be safely used as an implantable medical device in a human subject
without significant risk of bio-incompatibility.
[0134] FIG. 16 shows a magnified view 1600 of a pattern transferred
to the surface of an object using conformal template vacuum
bagging. The pattern includes two parallel lines 1605a and 1605b.
Each of the lines 1605a and 1605b has a width of significantly less
than 10 microns. In this example, the surface was coated with
Tecoflex MG8020. The flexible stamp used to imprint the lines 1605a
and 1605 was formed from PDMS. For illustrative purposes, contrast
was enhanced via metal deposition onto the surface of the object.
In particular, a 10 nm layer of titanium was deposited on the
surface of the object.
B. Micropatterned Implantable Balloons
[0135] Anchoring and adhesion to biological tissues are critical
for most cardiovascular implants. Cardiovascular plugs, occluders,
stents, and valves are typically anchored by one or more of the
following mechanisms: radial pressure against tissue, active
fixation with barbs or hooks that penetrate tissue, sutures, and
surgical adhesive or tissue glue. All of these mechanisms,
especially fixation by hooks and anchors could potentially cause
damage to tissues. A variety of technologies exist that provide
anchoring of implants with inflating balloons or other soft
conformable surfaces bringing the implant into contact with
surrounding tissues. These approaches can be useful because they
provide large areas of contact between the tissue and the implant
surfaces. They exert uniform forces against the tissues thus
facilitating anchoring of the implant. However, the extent to which
an implant is anchored utilizing these approaches can be limited by
the anatomy of the patient (which dictates the shape the balloon
with take) and the friction created between the tissue and the
surface.
[0136] The various concepts introduced above and discussed in
greater detail below may be implemented in any of numerous ways as
the described concepts are not limited to any particular manner of
implementation. Examples of specific implementations and
applications are provided primarily for illustrative purposes.
[0137] The subject matter disclosed herein relates to a patterned
balloon device including an expandable balloon wherein at least a
portion of the outer surface of the balloon includes a pattern. In
some implementations, the patterned balloon device enhances
friction and aids in anchoring of a first object to a second object
in an aqueous environment. The first object can be a medical
device, implant or any other biocompatible object, which needs to
be immobilized in a subject's body. The second object can be any
tissue, organ, or previously implanted biocompatible object in a
subject's body. The aqueous environment can be blood, lymph, saliva
or any other bodily fluid. For example, cardiovascular implants,
such as a stent supporting a blood vessel, must be anchored to the
tissue to remain in place in spite of all hemodynamic forces acting
on the implant inside the subject's body.
[0138] In some implementations, the balloon is radially or
outwardly expandable from a deflated state wherein the balloon has
a first volume to an inflated state wherein the balloon has a
second volume, which is greater than the first volume. In some
implementations, the inflated state of the balloon may have one or
more levels of expansion. For example, one or more portions of the
balloon may expand sequentially rather than simultaneously
depending on the amount of pressure required. In some
implementations, at least a portion of the outer surface of the
balloon is coated in anti-microbial, anti-bacterial and/or
anti-inflammatory substance. In some implementations, at least a
portion of the outer surface of the balloon is coated in an
adhesive substance to enhance contact with surrounding tissues or
organs. The balloon can be manually coated prior to implantation or
it can be provided pre-coated with one or more of the above
substances.
[0139] FIG. 17 illustrates an example patterned balloon device 1700
within a heart 1710 of a subject. The patterned balloon device 1700
includes an expandable balloon 1702 that can be deployed through a
catheter 1704. The balloon 1702 can be deployed from the catheter
1704 and a left atrial appendage (LAA) 1708 of the heart 1710 as it
is shown in the example in FIG. 17. Once deployed, the patterned
balloon device 1700 is immobilized to the LAA 1708 and can be
detached from catheter 1704. In some implementations, the patterned
balloon device 1700 immobilizes a biocompatible object in the LAA
1708. In some implementations, the patterned balloon device 1700 is
a surgical kit or other kit that includes the balloon 1702 and
catheter 1704. The balloon 1702 can be configured, selected, or
manufactured for the subject or patient into whom the balloon 1702
is implanted. The balloon 1702 can have a volumetric shape or
geometry that substantially matches the anatomical morphology of
the patient's LAA 1708. In some implementations, the balloon 1702
can include a plurality of lobes that when inflated substantially
complement the LAA shape of a specific subject. In some other
implementations, the balloon 1702 can be made complementary to the
shape of any other body cavity having an implant. In some
implementations, the morphology of a subject's LAA 1708 can be
ascertained by non-invasive computer tomography (CT) imaging. The
balloon 1702 can be non-spherical when inflated since a spherical
device may need to be over-inflated to fill a subject's LAA 1708.
The inflation of a spherical device can induce strain on both the
elastomeric material of the spherical device, the multi-lobular LAA
structures, and the tissue surrounding the LAA. Over-inflation of a
spherical device can also compress the circumflex artery that runs
underneath the LAA. In some implementations, the balloon 1702 can
be manufactured for a specific subject. The catheter 1704 is
configured for insertion through the subject's femoral artery. The
tip of the catheter 1704 is advanced through a subject's arterial
system toward the subject's LAA. The catheter 1704 includes an
elongate flexible body that can include PET, nylon, polyethylene,
polyether ether ketone, or any combination thereof. In some
implementations, the catheter 1704 is configured for insertion
through a laparoscopic or other surgical opening. In some
implementations, the catheter 1704 has a length between about 50 cm
and about 150 cm. In some implementations, the outer diameter of
the catheter 1704 is between about 0.2 mm and about 6 mm, between
about 0.5 mm and about 5 mm, between about 0.5 mm and about 4 mm,
and between about 1 mm and about 3 mm. In some implementations, the
catheter 1704 includes a solid core to enable the deployment tip of
the catheter 1704 to be controlled. For example, the core can
include a stainless steel, nitinol, nickel titanium alloy, or
polymeric materials that can be rotated by the surgeon to control
the rotation of the catheter 1704. In some implementations, the
catheter 1704 includes radiopaque to enable the surgeon to
visualize the placement of the catheter 1704 within the patient
with the use of X-ray imaging. In some implementations, the
catheter 1704 includes an inflatable balloon. The inflatable
balloon is configured to inflate and at least partially block the
LAA during the deployment of the balloon 1702.
[0140] In some implementations, the patterned balloon device
includes a pattern, which enhances friction with the application of
pressure between tissues and the patterned surface of the balloon.
For example, FIG. 18 shows a pattern 1800 that can be used to
enhance friction. However, other patterns also may be selected. For
example, patterns can be selected to help move fluid away from the
interface between the patterned balloon surface and tissues, and/or
deform or penetrate tissues to increase surface area or provide
mechanical interlocking between the patterned balloon device
surface and tissues. In some implementations, the pattern can be a
hexagonal array inspired by tree frogs as described above in
connection with Section A. Other patterns may also provide pathways
for fluids such as blood to be displaced allowing for areas of dry
contact dry contact between tissues and the patterned balloon
device. Other array patterns can also include cylindrical,
rectangular, spherical, polygonal, triangular, circular, and
ellipsoid features or any geometrical shape suitable for increasing
contact friction or any combination thereof. In some
implementations, the selected pattern can be a corrugated pattern,
which can deform tissues increasing the surface area of contact. In
some implementations, the pattern is a microneedle pattern, such as
the pattern 1900 shown in FIG. 19, which can penetrate or interlock
with tissues. The pattern can be a micro- or nano-pattern depending
on the size of an individual feature in the pattern. The pattern
can also be a combination of micro- and nano-patterns. In some
implementations, the pattern is embedded in the walls of the
balloon as part of the design. In some implementations, the pattern
is attached to the outer surface of the balloon in a permanent or a
removable manner. In some implementations, the pattern encompasses
the whole outer surface of the balloon. In some implementations,
the pattern covers at least a portion of the outer surface of the
balloon. In some implementations, the pattern includes features
uniformly distributed in an array. In some other implementations,
the pattern includes a higher number of features distributed in at
least a portion of the patterned and a lower number of features
distributed in another portion of the pattern, forming a
non-uniform distribution. In some implementations, features can be
disposed perpendicularly to the surface. In some other
implementations, features can be disposed at an angle to the
surface or to be slanted. In some implementations, all features are
slanted in the same direction. In some other implementations,
features in the same array can be slanted in different directions
or they can be perpendicular.
[0141] FIG. 20A illustrates an example patterned balloon device
1700 in an uninflated state. FIG. 20B illustrates a cross-sectional
view of the example patterned balloon device 1700 in an inflated
state. The inflated state can be any state where the balloon 1702
is expanded with respect to the configuration of the balloon 1702
prior to being deployed, for example when the patterned balloon
device is within the catheter 1704. The balloon 1702 can be
expanded or otherwise inflated with a fluid, gas, foam, or other
material. In some implementations, the balloon 1702 can be
self-expanding. For example, the walls of the balloon 1702 can
include nitinol ribs that deploy to an expanded state once the
patterned balloon device 1700 is deployed from the catheter 1704.
In some implementations, the patterned balloon device 1700 includes
a valve 1712 through which the balloon 1702 can be filled. The
valve 1712 can enable a lumen 1722 to be inserted in a first
direction and into an interior space of the balloon 1702 but
substantially prevents fluid from flowing in the opposite
direction. The balloon 1702 can be monolithically integrated with
the valve 1712. The valve 1712 can enable a surgeon to fill the
balloon 1702 without leakage once disengaged from the catheter
1704. The balloon device 1702 can be filled with a hardening
material to stabilize the balloon 1702 within the body cavity or in
the example the LAA 1708 after implantation. The fluid to inflate
the balloon 1702 can be passed to the interior of the patterned
balloon device 1700 via a lumen 1722. In some implementations, the
lumen 1722 is inserted through a valve 1712 during the patterned
balloon device's non-deployed state, for example when the balloon
1702 is in the catheter 1704.
[0142] The valve can be monolithically integrated into the
patterned balloon device 1700 during the molding process.
Monolithically integrating the valve 1712 with the patterned
balloon device 1700 can enable the balloon 1702 to be inflated to a
high pressure without delamination of the valve 1712 from its walls
of the patterned balloon device 1700. The valve 1712 can include a
polymeric septum that is pierced by lumen 1722. Once the patterned
balloon device 1700 is deployed and secured in the LAA 1708, the
lumen 1722 can be retracted. The polymeric septum valve can seal
the location where lumen 1722 previously pierced the septum,
sealing the interior of the patterned balloon device 1700. The
valve 1712 can also include a cured material, for example quick
setting epoxy can be applied to the opening left by the retracted
lumen 1722. The valve 1712 can include a mechanical valve that is
open to fill the balloon 1702 and then closed once the balloon 1702
is filled. The valve 1712 can include wings 1714, coupled to the
internal side of the valve 1712 to protect the opposing wall of the
patterned balloon device 1700 from being pierced accidentally by
the lumen 1722 during deployment of the filling of the balloon
1702. A portion of the valve 1712 can extend past the walls of the
balloon 1702. The portion can include attachment anchors 1718,
which can be sutures. The attachment anchors can be used to secure
and anchor the patterned balloon device 1700 to the surrounding
tissues such as the LAA 1708. In some implementations, the
attachment anchors 1718 can be coupled with the outer surface of
the wall 1720 of the patterned balloon device 1700.
[0143] In some implementations, the balloon 1702 of the patterned
balloon device 1700 can be fabricated using rapid prototyping
techniques, such as direct 3D printing of polyurethane materials or
molding from 3D printed templates of silicone materials. These
materials can have a wide range of stiffness (ranging from kPa to
tens of MPa) and extensibilities (e.g., up to 700%). In some
implementations, the material used to fabricate the balloon 1702 is
intrinsically soft as to not damage tissues or impede their
function. In some implementations, the material used to fabricate
the balloon 1702 is robust enough to withstand the forces exerted
on the device when implanted. In some implementations, the
patterned balloon device 1700 can include polyurethane, silicone,
nylon, PET, or a combination thereof. In some implementations, the
walls 1720 (or other components of the balloon 1702) can include a
non-stretchable polymer, such as polyethylene terephthalate (PET),
polytetrafluoroethylene (PETE), nylon, or polyvinyl chloride (PVC).
In some implementations, the walls 1720 of the balloon device 1702
can be reinforced with fabric, metal mash or wire, or other
materials.
[0144] In some implementations, the balloon 1702 can be
manufactured using a mold that includes both a hard portion
(Veroclear, Stratasys) and soft portion (Tango+, Stratasys). One
mold can be manufactured for each side of the balloon 1702. Each
mold can be filled with a homogeneous silicone blend of 69 wt %
Dragon Skin.RTM.20 (DS20; Smooth-On, Inc.), 10.3 wt % Silicone
Thinner.RTM. (Smooth-ON, Inc) and 20.7 wt % Sylgard.RTM.184
mixture. The silicone blend and molds can then be baked in an oven
at 100.degree. C. for 35 minutes. Nest, the partially cured
silicone blend can be removed from the molds. The two halves of the
balloon 1702 can be aligned and bonded together with DS20
pre-polymer. The coupled halves can be returned to the oven at
100.degree. C. for one hour. Pure DS20 can be used instead of the
silicone blend for the seams because pure DS20 has a higher
viscosity and stays in position after placement on the seam, Once
fully cured and cooled, the balloon 1702 can be plasma treated and
soaked in 12 vol % 3-glycidoxypropyltrimethoxysilane (GPTS; Sigma
Aldrich) for one hour. After cleaning and drying, the balloon 1702
can be rinsed in a solution of .about.10 wt % PCU in DMAC (e.g.,
provided by Sigma Aldrich). The balloon 1702 can be baked in an
over at 70.degree. C. for 2 hours, and then dipped again into PCU
solution. The balloon 1702 can be placed in a 70.degree. C.
overnight to fully cure PCU surface coating. In some
implementations, other injection molding processes can be used to
manufacture patterned balloon devices described herein.
[0145] FIGS. 21A-21C and 6A-6D illustrate example methods for
implanting a patterned balloon device 1700. The patterned balloon
device 1700 can be deployed via a number of procedures. In some
implementations, the patterned balloon device 1700 can be deployed
via a transcatheter method or surgically. For example, inflated
from the ostium of the LAA 1708 or from the distal end of the LAA
1708. FIGS. 21A-21C illustrate an example patterned balloon device
1700 during different stages of transcatheter deployment. FIGS.
21A-21C illustrate deployment of patterned balloon device into an
in vitro testing system 1706. The in vitro testing system 1706
includes an artificial LAA 1708. While illustrated in relation to
the in vitro testing system 1706, the patterned balloon device
described herein is also configured for in vivo testing. FIG. 21A
shows the patterned balloon device 1700 contained within catheter
1704. The patterned balloon device 1700 can be fully contained with
the catheter 1704 in an undeployed or deflated stated during the
procedure to snake the tip of the catheter 1704 from an insertion
site to the target body cavity or a subject's left atrium. FIG. 21B
shows the patterned balloon device 1700 after partial deployment
into the artificial LAA 1708 from catheter 1704. FIG. 21C shows the
patterned balloon device 1700 fully deployed into the artificial
LAA 1708. As illustrated in FIG. 21C, the catheter 1704 can be
retracted from the artificial LAA 1708 after deployment of the
patterned balloon device 1700. As illustrated in FIG. 21A, the
patterned balloon device 1700 can be collapsible to fit within the
catheter 1704 and then expanded to fir within a subject's LAA. In
some implementations, the balloon 1702 is expanded and deployed by
infusing a fluid into the balloon 1702. The fluid used to fill the
balloon 1702 can be cured (chemically, thermally, or with fiber
coupled to UV light) to ensure the deployed patterned balloon
device 1700 retained its shape and stayed immobilized or anchored
within the body cavity or the LAA. Furthermore, by solidifying the
liquid, potential issues of balloon rupture will be reduced. As
described above, the curable fluid is configured to have mechanical
properties, such that the solidified balloon 1702 can accommodate
the natural movement of body tissues such as the natural
contractions of the left atrium and other portions of the heart.
The balloon 1702 can be filled with epoxies, polyethylene glycol,
collagen-based biocompatible polymeric gels, silicon, polyurethane,
poly(methyl methacrylate), saline, self-expanding foam particles,
or any combination thereof. The fluid or other material that fills
and inflates the balloon 1702 can be referred to as an inflation
fluid. In some implementations, a contrast agent or radiopaque
material can be added to the filling of the balloon 1702 to make
the patterned balloon device 1700 visible to imaging devices. In
some implementations, the fluids used to fill the balloon 1702 are
stored in reservoirs that are coupled to the patterned balloon
device 1700 via the catheter 1704. The balloon 1702 can be filled
by injecting the fluid from the reservoir and into the balloon 1702
via the lumen 1722.
[0146] FIGS. 22A-22D illustrate an example patterned balloon device
1700 during the stages of deployment from the distal end of the LAA
1708. FIG. 22A illustrates a first step where a small incision is
made in the LAA 1708. The catheter 1704, which during the initial
steps contains the patterned balloon device 1700, attachment
anchors 1718, and a lumen 1722, is inserted through the incision
and in to the LAA 1708. As illustrated in FIG. 22A, purse string
sutures 600 are made near where the catheter 1704 is inserted into
the LAA 1708. FIG. 22B illustrates the retraction of the catheter
1704. As the catheter 1704 is retracted, the patterned balloon
device 1700 is deployed into and remains within the LAA 1708. FIG.
22C illustrates the filling (also referred to as the expansion or
inflation) of the balloon 1702. The lumen 1722 passes through the
valve 1712 and into the interior of the balloon 1702. The interior
of the balloon 1702 can be filled with fluid 602, such as liquid
epoxy. As the balloon 1702 is filler, the balloon 1702 expands to
fill the volume of the LAA 1708. After a predetermined amount of
time, the fluid 602 cures and hardens. In some implementations, the
patterned balloon device 1700 can be filled with a fluid or other
material that does not cure or otherwise harden over time, for
example saline. FIG. 22D illustrates the anchoring of the patterned
balloon device 1700 to the LAA 1708. The attachment anchors 1718
can be sutures that are tied or otherwise coupled with the purse
string sutures 600 placed in the LAA 1708. The attachment 1718 can
hold the patterned balloon device 1700 in place and within the LAA
1708. In some implementations, the attachment anchors 1718 can hold
the balloon 1702 in place as the fluid filling the balloon 1702
cures. In some implementations, the patterned balloon device 1700
does not include attachment anchors and immobilization is achieved
through friction forces generated between the patterned balloon
device 1700 and surrounding tissues or other implanted devices.
[0147] In some implementations, the patterned balloon device is
integrated into the body of the object, which is to be implanted.
In some implementations, the object is manufactured such that the
design of the object includes a patterned balloon device
permanently integrated. In some implementations, the patterned
balloon device is attached to the object prior to implantation. In
some implementations, the patterned balloon device is implanted
separately from the object depending on which surface of the object
requires anchoring to surrounding tissues or organs.
[0148] In some implementations, the patterned balloon device can
transition from a deflated state to an inflated state be
introducing gas, liquid or malleable semi-solid into the interior
of the balloon. The balloon can be inflated by a manual or
automatic pump or any suitable inflation device known in the art.
The patterned balloon device can be pressurized to a desired level.
In some implementations, once the patterned balloon device has been
inflated it yields a conformal contact with surrounding tissues or
organs such that the implant is anchored in place. In some
implementations, the portion of the patterned balloon device
forming a conformal contact with tissues or organs is maximized
allowing for the largest possible portion if not all of the
patterned surface to interface with tissues or organs, which would
yield the strongest attachment forces for the implant. In some
implementations, inflation of the patterned balloon device is
initiated once the implant is positioned in the target location in
a subject's body. For example, in the interior of a blocked blood
vessel.
[0149] In some implementations, the subject is a human patient in
need of medical device implantation. The subject can also be any
mammal such as a monkey, mouse, rat, dog, cat, sheep or ant animal
that requires medical device implant.
[0150] The subject matter disclosed herein also relates to a method
of fabrication of a patterned balloon device. The method includes
fabricating a thin-walled balloon by means known in the art such as
blow molding, dip coating, vacuum bagging, or conventional molding
or casting or a combination thereof. In some implementations,
fabrication of a patterned balloon device includes utilizing a
soluble core, which can be solubilized and removed following curing
of the balloon. In some implementations, the balloon is
prefabricated in the shape desired for the application.
[0151] The method also includes fabricating of the pattern. In some
implementations, patterns with a desired features or geometry are
fabricated on a planar template via methods known in the art such
as lithography, 3D printing, laser cutting, and stereolithography
or any combination thereof. Once patterns are formed on a planar
template, they can be transferred to flexible elastomeric masters.
These masters can either be used to cast the patterns in or to
emboss those patterns onto the balloon.
[0152] In some implementations, the method includes pattern
transfer. Pattern transfer can include, for example, bonding
patterns prefabricated in an elastomeric master to the surface of
the balloon through methods such as thermoplastic bonding, solvent
welding, or adhesive bonding or any combination thereof.
[0153] In some implementations, the method includes embossing
patterns on the balloon. Pattern embossment includes laminating the
patterned master in conformal contact to the balloon surface,
applying pressure and heat to thermoform the pattern in the balloon
surface.
[0154] FIG. 23 illustrates an example method 2300 for fabricating
an implantable balloon device. FIGS. 24A-24E show stages of
construction of an implantable balloon device according to the
method of FIG. 23. FIGS. 23 and 24A-24E are described together
below.
[0155] Referring to FIG. 23, the method 2300 may include
positioning a first portion of an inflatable balloon over a lower
portion of a sacrificial core (stage 2305). FIG. 24A depicts two
views of a sacrificial core 2402. The sacrificial core 2402
includes a hole 2404. The hole can be configured for receiving a
septum at a later stage of the method 2300. The salt core 2400 can
be designed to have an arbitrary geometry. For example, the
geometry can be based on volume rendered 3D segmentation from
patient CT images such that the salt core is shaped to fit into a
particular tissue region, such as the patient's LAA. Different
parameters such the location of a septum with respect under-sizing,
and irregularity of the geometry can be considered in the design of
salt core 2402.
[0156] In some implementations, a mold for the salt core 2402 can
be initially 3D printed, and can be inverted to a material such as
a highly extensible silicone mold made from Ecoflex. In some
implementations, fine particulate salt can be mixed with water
(e.g., with the ratio of 6 to 1) to form a slurry, and the slurry
can be put into the Silicone mold. Vacuum can be used to degas
entrapped bubbles. The silicone mold can be dried. For example, in
some implementations, drying can be done in two steps, including
using a 100.degree. C. oven for a first step and performing a post
bake of 2 hours at 140.degree. C. for a second step. The salt cores
2400 can be taken out of the silicone molds and stored for the next
stages of the method 200.
[0157] In some implementations, the balloon can be fabricated in
two halves using pressure forming of polyurethane films on 3D
printed molds. Thus, each half of the balloon can include a
respective polyurethane film. For example, a rigid material such as
Veroclear can be used to form a mold for the polyurethane film, and
the polyurethane film can be pressure formed (e.g., using a
MiniSTAR S.RTM., at approximately 5 bar) on the top and bottom of
Veroclear molds. After that each side of the balloon can be trimmed
to become a half balloon. FIG. 24B shows a half balloon 2406
pressure formed on a mold 2408. The half balloon 2406 has not been
trimmed yet in the depiction of FIG. 24B.
[0158] The method 2300 may include positioning a second portion of
the inflatable balloon over an upper portion of the sacrificial
core (stage 2310). In some implementations, the second portion of
the inflatable balloon can be formed from a polyurethane film in
the same manner described above in connection with FIG. 24B. For
example, the same mold 2408 can be reused to pressure form the
second half of the balloon. In some implementations, the second
half of the balloon can be positioned over the upper portion of the
sacrificial core such that the second portion of the inflatable
balloon at least partially overlaps the first portion of the
inflatable balloon. This is depicted in FIG. 24C, in which the
first half 2406a of the balloon and the second half 2406b of the
balloon are positioned over the sacrificial core.
[0159] In some implementations, the first half 2406a of the balloon
and the second half 2406b of the balloon may overlap by a distance
in the range of about 1 mm to about 3 mm. For example, the first
half 2406a of the balloon and the second half 2406b of the balloon
may overlap by a distance of about 2 mm. In some implementations,
an elastomeric string 2410 can be wrapped around the overlapping
portions of the first half 2406a of the balloon and the second half
2406b of the balloon, as depicted in FIG. 24C. For example, the
elastomeric string can be formed from a material such as Elastosil,
and can have a thickness in the range of about 250 microns to about
350 microns.
[0160] The method 2300 may include applying vacuum to the first
portion of the inflatable balloon and the second portion of the
inflatable balloon (stage 2315). In some implementations, vacuum
can be applied using a vacuum bag assembly similar to those
described above, for example, in connection with the method 200 of
FIG. 2. For example, the polyurethane-encased sacrificial core can
be wrapped inside a larger unpatterned elastomeric film. FIG. 24D
shows a plurality of such polyurethane-encased sacrificial cores
2414 ready to be processed in this manner, along with elastomeric
films 2416 and a vacuum bag 2418. In some implementations,
breathers can also be placed on each side of the elastomeric films
inside the vacuum bag 2418, and vacuum (e.g., about -0.75 bar) can
be applied. FIG. 24E shows six elastomeric films, each wrapped
around a respective polyurethane-encased sacrificial core, inserted
into the vacuum bag 2418 with vacuum applied.
[0161] The method 2300 may include applying heat to the first
portion of the inflatable balloon and the second portion of the
inflatable balloon to form a thermoplastic bond between the first
portion of the inflatable balloon and the second portion of the
inflatable balloon (stage 2320). For example, the vacuum bag 2418
can be placed inside an oven (e.g., around 100.degree. C.) for one
to three hours to form a thermoplastic bond between the first
portion of the balloon and the second portion of the balloon.
[0162] In some implementations, the method 2300 can include
inserting a septum into the sacrificial core (stage 2325). For
example, as depicted in FIG. 24C, a septum 2412 can be inserted
into the sacrificial core (e.g., into the hole originally formed in
the sacrificial core, as described above). In some implementations,
the septum can have a roughly cylindrical shape with a diameter of
about 2 millimeters and a length of about 6 millimeters. The septum
can be made from a polyurethane material such as
Tecoflex.RTM.--SG85A. To accomplish this, a mold of the septum 2412
can be designed, 3D printed from (e.g., using a material such as
Veroclear), and then inverted on a silicone mold. The silicone mold
can be filled with dry polyurethane pellets and placed inside a
vacuum oven (e.g., at the temperature of about 170.degree. C.) to
cause the pellets to melt. After the mold is fully filled with the
melted polyurethane, it can be cooled down and the septum 2412 can
be removed and inserted into the sacrificial core as shown in FIG.
24C.
[0163] The method 2300 may include positioning a third portion of
the inflatable balloon over the first portion of the inflatable
balloon (stage 2330) and positioning a fourth portion of the
inflatable balloon over the second portion of the inflatable
balloon such that the fourth portion of the inflatable balloon at
least partially overlaps the third portion of the inflatable
balloon (stage 2335). In some implementations, stages 2330 and 2335
of the method 2300 can be performed in a manner similar to that of
stages 2305 and 2310. For example, polyurethane films can be
pressure formed over a mold and trimmed to size, and then
positioned over opposite halves of the sacrificial core.
[0164] The method 2300 may include applying vacuum to the third
portion of the inflatable balloon, the fourth portion of the
inflatable balloon, and the septum (stage 2340) and applying heat
to the third portion of the inflatable balloon, the fourth portion
of the inflatable balloon, and the septum to form a thermoplastic
bond between the first portion of the inflatable balloon, the
second portion of the inflatable balloon, the third portion of the
inflatable balloon, the fourth portion of the inflatable balloon,
and the septum (stage 2345). In some implementations, these stages
may be performed in a manner similar to that of stages 2315 and
2320 described above.
[0165] In some implementations, the film used to wrap the
polyurethane encased sacrificial core for stage 2340 can be a film
having a pattern on its surface. The pattern can allow the film to
serve as a stamp. For example, such a stamp can be formed in a
manner similar to the flexible stamps described above in Section A
in connection with the method 200 of FIG. 2. Thus, in some
examples, a silicon wafer can be micropatterned using
photolithography techniques. After fully curing the wafer, it can
be inverted to a silicone (e.g., Sylgard) master template. After
spin coating with an elastomeric material such as Elastosil (e.g.,
at 800 RPM), the template can be cured, for example by exposure to
heat. Finally the elastomeric stamp can be peeled off, for use in
thermoplastic assembly using vacuum bagging. The vacuum and heat
can cause the pattern on the surface of the balloon to become
imprinted on a surface of the balloon, as described above.
[0166] The method 2300 may include dissolving the sacrificial core
(stage 2350). In some implementations, the septum of the
sacrificial core can be punctured with needles or luer-lock, and
attached to a perfusion system that circulates water. The perfusion
system can cyclically fill the balloon with water and infuses the
water out. Over these cycles, the sacrificial core can be fully
dissolved. Eventually, after dissolving the salt cores, the balloon
can be dried, for example with cyclic application of pressure and
vacuum. The final product after drying may be able to fit inside a
French 14 tube, as illustrated in FIG. 24F. For example, on the
left hand side of FIG. 24F is a balloon 2450 with a soluble
sacrificial core still intact and a needle 2452 puncturing a septum
of the balloon 2450. In the middle of FIG. 24 is shown a balloon
2454 whose sacrificial core has already been dissolved as described
above. On the right hand side of FIG. 24F is a balloon that has
been dried and placed inside a FR 14 tube labeled 2456.
C. Thin Inflatable Actuators
[0167] Surgery is an invasive medical procedure requiring incisions
of varying sizes, which carries with it an inherent risk. Incisions
made by even the most skillful surgeons can leave painful wounds
that take a long time to heal and form scar tissue. Therefore, the
medical field has been moving toward replacing surgeries with
minimally invasive procedures whenever possible. These procedures
limit the size of incisions required and thus lessen the
wound-healing time, associated pain, and risk of infection.
Advances in various medical technologies have made the transition
feasible. For example, the advancement of imaging techniques has
allowed radiologists to operate interventional instruments through
catheters instead of large incisions. Additionally, specialized
medical equipment may also be used, including fiber optic cables
and miniature video cameras, which increases precision and
safety.
[0168] However, issues have arisen from the rigid nature of
currently available surgical robots. These tools are based on the
interaction of metal with soft tissues, which can cause unwarranted
physical damage and jeopardize patients. There is a major need in
the field for the production of safer medical devices made of
compliant materials.
[0169] Soft robotics is a sub-field of robotics, which refers to
constructing robots from highly compliant materials, similar to
those found in living organisms. Organisms, such as Echinoderms
(starfish, sea urchins) and Cnidarians (jellyfish) are ancient and
relatively simple organisms, capable of movement beyond the reach
of even the most advanced hard-robotic systems. Soft robotics draws
heavily from the way these living organisms move and adapt to their
physical surroundings. Unlike robots built from rigid materials,
soft robots allow for increased flexibility and adaptability for
accomplishing tasks while simultaneously decreasing risks for
humans. These characteristics make soft robots highly desirable in
the field of medicine.
[0170] The subject matter disclosed herein relates to a soft
robotic device, which includes a first layer and a second layer
bonded together. One or more of the layers may consist of
extensible thermoplastic thermoelastic material. In one embodiment,
one of the layers might be of a relatively stiffer, inextensible
material compared to the other layers. The first and second layers
may be directly bonded to each other or they may be bonded through
one or more intervening layers. Additionally, the soft robotic
device disclosed herein, can have an initial conformation in which
there is negligible, low-volume in the interior of the device. The
low-volume initial conformation enables the device to fit within
spaces of small diameters such as catheters. In one embodiment,
soft robotic devices also include a network that can be located in
between the first and the second layers or any of the layers
included in the device. This network can be pressurized in order to
actuate the soft robotic device with a pneumonic mechanism
facilitate a transition of the soft robotic device to from a flat,
low-volume or zero-volume conformation to an extended or actuated
conformation.
[0171] In one embodiment, the soft robotic device can be a bending
device, a rotary device, a robotic swimmer, or a gripping device,
which can be utilized in performing mechanical tasks such as moving
objects in space. In another embodiment, the soft robotic device
can be a heart valve or a stent and be utilized in the field of
medical devices.
[0172] The subject method disclosed herein also relates to a laser
welding method for constructing a soft robotic device. The method
includes heat-pressing two or more layers together. In an
embodiment of the laser welding method, the layers are polyurethane
films. The method also includes laser welding a desired pattern
from the heat-pressed layers.
[0173] The subject method disclosed herein further relates to a
thermobonding method for constructing a soft robotic device. The
method includes cutting a layer into a pattern. In an embodiment of
the thermobonding method, the layer is water-soluble. The method
also includes heat-pressing the layer between two or more external
layers. In an embodiment, the external layers are polyurethane
films. The method further includes dissolving the initial internal
layer and cutting along seams, which formed following
heat-pressing.
[0174] Soft robotic devices are based on cephalopods: animals
without a skeleton, like octopus and squid. They mimic the
movements of the cephalous by pressurizing a soft device having
embedded channels. Soft robotics can be actuated using pneumatic
pressure to cause the robot to undergo a range of motions. The
basic soft robotic actuator includes an extensible channel or
bladder that expands against a stiffer or less extensible backing.
Soft robotic devices utilize soft materials, such as soft
elastomer, or flexible materials, such as papers and a nitrile.
Soft robotic systems can provide a complex range of motions when
different parts of the system are pressurized independently or in
sequence. The soft robotic devices can be integrated into
subject-specific, anatomically-guided shapes that would optimize
access while increasing dexterity for micromanipulation in an era
of increasingly complex percutaneous interventions.
[0175] Thermoplastic materials are polymers, which can become
pliable or moldable when heated above a specific temperature and
solidify upon cooling. Most thermoplastics have a high molecular
weight and melt into a molten state relatively quickly.
Thermoplastic materials have long polymer chains linked through
intermolecular forces such as van der Waals forces, forming linear
or branched structures. With increased temperatures, these
intermolecular forces weaken rapidly, yielding a viscous liquid.
Thus, thermoplastics may be reshaped by heating and are typically
used to produce parts. However, each particular thermoplastic
exhibits different physical properties, making it critical to
select the right material for the application at hand. Examples of
thermoplastic materials include but are not limited to
polyurethane, high-pressure polyethylene, low-pressure polyethylene
elastic, polystyrene, polyamide, and polyvinyl chloride (PVC).
[0176] The subject matter disclosed herein relates to a soft
robotic device, which can have multiple conformations including an
unactuated or non-expanded conformation, an actuated or
extended/inflated conformation, and an initial conformation in
which there is negligible volume in the interior of the device.
This initial conformation can be referred to as a "low-volume" or a
"zero-volume" initial conformation of the soft robotic device. The
"low-volume" initial conformation may also refer to a soft robotic
device, in which there is virtually zero-volume or zero-volume
visually present in the interior of the device. In a low-volume
conformation, the sides of the soft robotic device may be collapsed
onto each other. For example, the soft robotic device can be
substantially planar in its low-volume initial conformation. A
low-volume initial conformation device may require an additional
step of collapsing and expanding such as rolling it up and then
unrolling it before actuation. The low-volume initial conformation
enables the device to fit within spaces of small diameters such as
catheters. For example, the low-volume initial conformation of the
device can be a rolled up conformation that allows the device to be
inserted into a catheter. These soft robotic devices may be
scalable in size depending on purpose of use and can be utilized in
a number of fields including but not limited to soft robotics
engineering to facilitate directional movement of robots, minimally
invasive surgery to control the movement of robotic arms or
gripping devices, and trans-catheter delivery of medical devices or
tissues such as prosthetic heart valve delivery through a catheter
system. In an embodiment, the thickness of the soft robotic device
is less than 70 .mu.m. In another embodiment, the thickness may
exceed 70 .mu.m.
[0177] The soft robotic device includes a first layer and a second
layer bonded together. One or more of the layers may consist of
extensible thermoplastic material such as polyurethane or any other
polymer that may be suitable for the purpose of expanding under
applied pressure. In one embodiment, at least one of the
thermoplastic layers might be made of a thermoelastic material.
Thermoelastic materials change elasticity with changes in
temperature, such that when thermal energy is added to an elastic
material, the material expands. Thermoplastic polyurethane is a
type of a thermoelastic material. Thermoelastic materials also
include rubber-like polymers. In one embodiment, one of the layers
might be of a relatively stiffer, inextensible material. In another
embodiment, one or more reinforcing layers can also be included,
such as a paper or mesh fabric. The first and second layers may be
directly bonded to each other or they may be bonded through one or
more intervening layers.
[0178] In one embodiment, all layers included in the soft robotic
device may be of the same thickness. In other embodiments one or
more of the layers may have a variable thickness along their
length. One or more of the layers may be thicker or thinner than
one of more of the other layers along their entire length.
Additionally, soft robotic devices may utilize differences in layer
thicknesses to create the differences in extensibility used for
actuation. For example, a thicker layer might not expand upon
pressurization to the same extent as a thinner layer would. The
difference in expansion can create curvatures in the design of the
actuated soft robotic device.
[0179] Soft robotic devices can also include a network that is
located in between the first and the second layers or in either of
the layers, or in a third central layer positioned between the
first and second layers. In an embodiment, the network is
pneumatic, meaning it contains and/or is operated by air or another
gas that is under pressure. The pneumatic network can be
pressurized in order to actuate the soft robotic device. In another
embodiment, the network may be actuated by utilizing a fluidic
system, may be electric, or optical. Pressurizing the network
allows for the soft robotic device to transition from a relatively
flat, low-volume or zero-volume conformation to an extended or
actuated conformation. The network may be pressurized using any
suitable pressurizing device or pump. In an embodiment, soft
robotic devices made from a thermoplastic material can return back
to an initial conformation after pressurization. In one embodiment,
plastic materials that cannot undergo an elastic recovery may be
used for single-actuation soft robotic devices. In one embodiment,
wherein one or more of the layers is made of a relatively
inextensible material compared to the other layers in the soft
robotic device, the inextensible layer may require a greater
pressurizing force for expansion and extension of the inextensible
layer may not occur even after pressurizing the network.
[0180] In one embodiment of the subject matter disclosed herein, a
thermobonding method for constructing a soft robotic device may be
the method of choice in order to minimize thickness of the device.
As described in FIG. 25 (left), this method includes inserting a
pre-cut layer pattern between two or more external layers and
directly sealing the layers using a heat press. In an embodiment,
the external layers are thermoplastic films. The layer pattern
defines a pneumatic network between the two or more external
layers. In one embodiment, the pre-cut layer has a higher
transition temperature compared to other layers included in the
device in order to prevent bending. In one embodiment, the pre-cut
layer is made from a material that can be dissolved after thermal
bonding, for example water-soluble films are used for more
effective actuation of the pneumonic network. The thermobonding
method may result in a more desirable or higher burst strength of
the soft robotic device. Furthermore, thermoplastic materials can
become pliable or moldable above a specific temperature and
solidify upon cooling.
[0181] In some embodiments the subject matter disclosed herein
relates to a laser welding method for constructing soft robotic
devices. Laser welding using a CO.sub.2 laser provides a cheap and
rapid method for soft robotic device construction. As described in
FIG. 25 (right) this method includes forming of the soft robotic
device by applying heat, pressure, or both to sheets of
thermoplastic material. The laser welding method further includes
laser heating or welding applied to those areas where bonding is
desired. In one embodiment, heating and/or pressure can be applied
by physical contact with a hot surface, or by laser heating or any
conventional methods. In those areas where heat is applied, the
thermoplastic materials can soften and bond together. The soft
robotic device can then be cooled in order to resolidify the
thermoplastic materials and to form a solid bond. In some
embodiments, additional layers can be bonded to the laser welded
layers in order to achieve solid impermeable layers since the laser
welding method may cut the layers it seals them, leaving holes in
the device.
[0182] FIGS. 26A-26D depict different conformations for two
embodiments of a soft robotic device. FIG. 26A shows an unactuated,
low-volume initial conformation of a bending device with a flat
geometry. FIG. 26B shows an actuated conformation of a bending
device with a flat geometry. Following pressurization, one or more
layers can expand to a higher degree compared to one of more of the
other layers allowing for the bent shape of the actuated
conformation. FIG. 26C shows an unactuated, low-volume initial
conformation of a soft robotic device with complex geometry. FIG.
26D shows an actuated conformation soft robotic device with complex
geometry.
[0183] FIG. 27 illustrates actuation of a soft robotic device, a
prototype heart valve according to one or more embodiments. In this
embodiment, at rest (left), the soft robotic device is rolled up in
low-volume initial conformation. This conformation allows for the
prototype heart valve to fit into spaces with small diameters such
as catheters and other medical devices. Once unrolled, the
prototype heart valve assumes an unactuated conformation such that
the layers of the device remain flat (center). Once pressurized,
the pneumatic network expands and bows outward in an actuated
conformation, causing "fingers" to bend away (right).
[0184] Soft robotic devices can be made of soft and compliant
materials such as polymers-metal composites, elastomers, and
hydrogels. These soft robotic devices operate based on pneumatic,
electrical, chemical, and optical actuation mechanisms. Soft
robotic devices with pneumatic actuation mechanisms include a
series of interconnected inflatable chambers, which can be made
from elastomers, fabrics, or a combination of both types of these
materials. The geometry and material properties of these chambers
dictate the motion of the device, upon actuation. Fabrication can
be achieved by rapid casting with two-part mixtures of liquid
elastomer precursors into 3D printed molds with manually embedded
fabrics. Although this process is relatively simple compared to
other manufacturing methods for soft and hard robotic devices, the
full process of creating a new design for an actuator can take
several hours, since it requires the following steps: i) design
geometry in CAD, ii) 3D print mold, iii) prepare and degas
elastomer, iv) pour and bake elastomer (with or without fabric
layers), and v) de-mold and bond parts of an actuator. Furthermore,
fabricating thin (<0.5 mm) soft robotic devices can be
particularly challenging since currently typical 3D printed parts
do not provide sufficient resolution, and de-molding such thin
features can be difficult. Thin soft robotic devices can be
constructed by means of soft lithographic techniques,
photolithography, and micro-casting. Alternatively, thin soft
robotic devices can be constructed using membrane micro-embossing
by excimer laser ablation (MeME-X). These methods, although
effective, are laborious and time-consuming, limiting their
adoption to a broader community. A simple fabrication method for
the development of small-scale soft robotic devices with a
pneumatic actuation mechanism can be based on dip-coating of
cylindrical templates. A drawback to the simplicity of this method,
however, is that only a limited number of designs can be fabricated
easily. Therefore, a simple yet versatile method that allows the
production of thin actuators with arbitrary features is desirable
for soft robotics applications.
[0185] The subject matter disclosed herein also relates to a simple
and effective laser welding method for rapid fabrication of thin
soft robotic devices. In an embodiment, the thin soft robotic
devices may utilize a pneumatic mechanism of actuation. In another
embodiment, the soft robotic devices can utilize an electrical,
chemical or optical actuation mechanism or any combination of these
mechanisms or any other suitable mechanism that would lead to
activation of the soft robotic device. The method includes
simultaneously cutting and laser welding a stack of thin films made
of thermoplastic polyurethane. The method may further include
utilizing inexpensive and commercially available materials and
tools for constructing soft robotic devices. In an embodiment, the
thickness of the soft robotic devices is 70 .mu.m or less. In
another embodiment the thickness can be more than 70 .mu.m. In an
embodiment of the laser welding method embodiment, several
different types of thin soft robotic devices can be constructed,
whose motions occur in-plane and out-of-plane. The soft robotic
devices constructed via the laser welding method can also include
grippers for pick and place applications and a swimming soft robot.
The trajectory of these soft robotic devices can be modeled using
Finite Element Method (FEM).
[0186] The laser welding method for constructing soft robotic
devices includes laminating layers by means of a heat press as
illustrated in FIG. 28A, which ensures that polyurethane layers are
flat and in conformal contact without creating a permanent bond
between the layers. The layers may be thermoplastic polyurethane
films. The method further includes cutting out a desired shape of
the soft robotic device under constructing using a laser-cutting
machine. The laminated layers can also be welded by the
laser-cutting machine. In an embodiment of the laser welding method
embodiment, a single pass of a laser beam can both cut and bond the
edges of the layers of the soft robotic device, forming a sealed
soft robotic device as shown in FIG. 28B. In an embodiment of the
laser welding method, the soft robotic device under construction
can be functional immediately after the cutting process. In one
embodiment of this method, a two-layered soft robotic device can be
constructed that can hold .about.10 psi for a square geometry with
a size of 20.times.20 mm. In another embodiment, the soft robotic
device constructed via the laser welding method can hold more or
less than 10 psi for any square geometry larger or smaller than
20.times.20 mm. In some embodiments, the two layers bonded as
described above can form a single actuator. In some embodiments,
additional actuators (e.g., formed from additional layers) can be
laminated to the first actuator, such that the soft robotic device
includes more than one actuator.
[0187] In one embodiment of the subject matter disclosed herein,
the soft robotic device is a bending soft robotic device. The
bending device can be made by utilizing an asymmetrical profile
achieved by making one side of the soft robotic device thicker or
less compliant than the other side. This allows for the bending
device to bend upon inflation due to asymmetric stiffness and
strain on the sides as demonstrated in FIG. 28C showing a 4-layer
soft robotic device (Actuator Type I), with in-plane symmetry. The
inflated soft robotic device is bounded by single and triple
layered films as shown in FIG. 28C, which leads to the asymmetry
across the actuator. The bending motion of the bending device
embodiment is shown in FIG. 29A. FIG. 29B shows a heat-map of
maximum principle strain in different portions of the bending
device while in ultimate bent configuration. FIG. 29C shows a
comparison between the simulated and experimental lateral
displacements of a thin soft robotic device using FEM
simulation.
[0188] In one embodiment, an asymmetrical profile for a soft
robotic device can be achieved by applying specific geometrical
construction. For example, FIG. 30A depicts a soft robotic device
with a geometry consisting of several pockets, which are connected
only on one side (soft robotic device of Type II). In one
embodiment, the motion of a soft robotic device of Type II can
occurs in-plane as demonstrated in FIG. 30B.
[0189] The motions for both Type I and Type II soft robotic devices
with in- and out-of-plane bending can be accurately simulated using
a Finite Element Method (FEM) as shown in FIG. 30C as well as FIGS.
30C and 30D. In an embodiment of the bending device embodiment, the
level of strain for bending devices of Type I and Type II is less
than 15%. Furthermore, the majority of the soft robotic device may
undergo even lower levels of strain, less than 5%. In comparison,
conventional soft robotic devices might require more than 50%
strain. In another embodiment, the level of strain for bending
devices of Type I and Type II can be more than 15%.
[0190] In one embodiment, the mechanism of bending for these soft
robotic devices is primarily dependent on folding of the walls of
the chambers, which is fundamentally different than most soft
robotic devices, which rely on large levels of strain of the
chamber walls. As shown in FIGS. 30C and 30D, soft robotic devices
of Type II can have a lower and more uniform strain distribution
for nearly the same degree of bending.
[0191] In one embodiment of the laser welding method embodiment,
design of functional soft robotic devices with complex motions such
as a rotary or a linear device can be achieved by changing the
design of the CAD file used to laser cut the devices. In one
embodiment of the subject matter disclosed herein, the soft robotic
device is a rotary device. Designing a rotary device consists of
generating a curved tube with a flattened cross-sectional area. The
cross section can be compared to a Bourdon tube, which is
rectangular where its longer side is parallel to the normal of the
plain of the curved tube. Upon inflation, the cross section can
tend towards a nearly round shape causing the tube to straighten
out. In one embodiment, relating the tip displacement to the
pressure inside the tube can be used as a pressure sensor. A rotary
device can also be utilized as a hydraulic soft robotic device for
Micro-Electro-Mechanical Systems (MEMS) or in soft surgical robots.
In some embodiments, a soft robotic device can be configured to
actuate in a combination of rotary, linear, and or other motion
patterns. For example, the pneumatic network contained within a
device (e.g., one or more channels or tubes) can be arranged in a
pattern such that, when inflated, the device can exhibit both
rotary motion and linear motion, or any other combination of types
of actuation. In some embodiments, the cross section of the thin
soft robotic device can be flattened in-plane whereas that of the
Bourdon tube is flattened out-of-plane as shown in FIG. 35. Upon
inflation, the thin rotary soft robotic device can curl up whereas
the Bourdon tube straightens as exemplified in FIG. 35.
[0192] FIG. 31A demonstrates how a spiral curve can act as a rotary
device. In an embodiment, upon inflation the spiral curve can
rotate up to 300.degree. at the pressure of 4.5 psi. In another
embodiment, the rotary device can rotate more than 300.degree. at
pressures less than or more than 4.5 psi. A curved tube design can
be further applied to produce axial and biaxial soft robotic
devices by defining a proper unit cell. For instance, axial soft
robotic devices can be developed from combination of semi-circle
curves, with an S-shaped unit cell as shown in FIG. 31B. This unit
cell is known as a horseshoe serpentine structure and can be used
for stretchable electronic applications. Each semi-circle curve can
curl up upon inflation and thus the overall length of an S-shaped
unit cell can be decrease. In one embodiment, changing the shape
and total number of unit cells can modify the overall displacement
of the linear soft robotic device. For instance, a linear device
with 15 unit cells might generate approximately 20 mm displacement
at a pressure of 7 psi, suggesting each unit cell displaces 1.3 mm
as shown in FIG. 31B. The developed axial soft robotic device can
be extended to a biaxial soft robotic device as shown in FIG. 31C,
by extending the array of unit cells in 2D. The S-shaped unit cell
can be rotated 90.degree. and joined to itself to create the unit
cell of the biaxial actuator. The overall displacement in each axis
can be linearly proportional to the number of S-shaped unit cells
used in that direction. For example, a biaxial actuator as shown in
FIG. 31C, which has 15 and 6 unit cells along x and y directions,
respectively, shrinks by 20 and 7.4 mm at a pressure of 7 psi.
[0193] In one embodiment, a soft robotic device of Type I can
function as a bi-directional device by being inflated between its
different layers. Specifically, inflating the chamber bounded by
layers 1 and 2 can result in a clockwise motion, and inflating the
chamber bounded by layers 3 and 4 can result in a counter clock
wise motion as shown in FIG. 32A. In another embodiment, the soft
robotic device is a soft gripper. A soft gripper can be constructed
by combining two bi-directional soft robotic devices with a robotic
arm. In an embodiment of the soft gripper embodiment, the soft
gripper is capable of performing pick and place tasks. FIGS. 32B
and 32C show the unactuated (left), actuated open (center), and
actuated closed (right) conformations of the soft gripper, as well
as images taken during the pick-and-place operations for various
objects. In an embodiment of the soft gripper embodiment, the soft
gripper can lift an object with a mass of 2.66 g at a pressure of
41 kPa (6 psi) in its open conformation. In another embodiment, the
soft gripper can lift an object with a mass of more or less than
2.66 g at pressures below or above 41 kPa (6 psi). Furthermore, in
an embodiment of the soft gripper, the soft gripper can weigh as
little as 0.098 g and can lift an object 30 times heavier than its
own weight. In another embodiment the soft gripper can weight more
or less than 0.098 g and lift an object more or less than 30 times
its own weight.
[0194] In one embodiment, the soft robotic device may be a four-arm
swimming robotic device referred to as a robotic swimmer hereafter.
The CAD file can be directly fabricated into a robotic swimmer in
one step without requiring any assembly. Each arm can have two
degrees of freedom (DOF) and consist of two bending devices. The
first soft robotic device can be of Type II with in-plane bending
motion, functions as the arm of the swimmer, and the second soft
robotic device can be of Type I with out-of-plane bending motion,
acting as a fin as shown in FIG. 33A. The palm of this robotic
swimmer can be a circular balloon that connects the fin to its arm.
In an embodiment, the palm can inflate more than the rest of the
arm, due to its large and circular surface area, serving as the
point of contact of the robotic swimmer to the water ensuring the
arm stays level with the surface of the water during actuation. In
another embodiment, the palm can inflate as much as or less than
the rest of the arm. In one aspect, the robotic swimmer can be as
light as 0.62 g allowing it to float in both its actuated and
unactuated conformations. In another aspect, the robotic swimmer
can weigh more than 0.62 g. The robotic swimmer can be powered by a
mini compressor or any other pressure source and can be controlled
by a microcontroller that controls two three-way valves. In one
aspect, as shown in FIG. 33B the robotic swimmer includes mirrored
soft robotic devices allowing the robotic swimmer to move in the
opposite direction. FIGS. 33C and 33D show the unactuated (left)
and actuated (right) configurations of the forward swimming robotic
swimmer positioned upside down (i.e., laying on its back) to better
visualize its motion.
[0195] FIG. 34A shows a sequence of images depicting the forward
swimming motion of the robotic swimmer for a single cycle, where a
cycle consists of an inflation and deflation phases. In an
embodiment of the robotic swimmer embodiment, the arms of the
robotic swimmer bend gradually and produce little thrust. That can
be achieved with a low flow rate of the compressor. In an
embodiment, the flow rate of the compressor is 250 ml/min or less.
In another embodiment, the compressor flow rate can be more than
250 ml/min. In an embodiment of the robotic swimmer embodiment,
during the deflation phase the arms are allowed to return to their
original position quickly, creating a relatively greater thrust
than during inflation phase. Therefore, the inflation phase can
serve as the recovery stroke, and the deflation phase can serve as
the power stroke for this swimming robotic device. FIG. 34B shows
the pressure inside the robotic device during the inflation and
deflation phases. The graph shows that the inflation can occur in a
near linear fashion, while the deflation can occur exponentially.
FIG. 34C shows the displacement of the robotic device for the
deflation and inflation phases over a series of seven cycles.
Initially during the first three cycles, the robot can have a near
zero movement during its inflation phase and a progressively
increasing displacement during its deflation phase. In one
embodiment, the average velocity of the robotic device can be 6.7
mm/s over the seven cycles as shown in FIG. 34D. In another
embodiment, the robotic swimmer can have an average velocity above
or below 6.7 mm/s. In an embodiment, the robotic swimmer can pull a
load as heavy as 127 g, which is 204 times its own weight. In
another embodiment, the robotic swimmer can pull any load heavier
or lighter than 127 g.
[0196] In one aspect, two layers can be laminated and laser welded
into square balloons. The average burst pressure of the balloons
can be measured for any constant power ranging from 10% to 90% and
the speed varied from 10% to 100% as shown in FIG. 36. In an
embodiment, the balloons can be made with the power ranging between
30% and 90% and the speed ranging between 20% and 90%. Average
burst pressure of 10.5 psi can occur in the case of 50% power and
10% speed.
[0197] In one aspect of the robotic gripper utilized for the pick
and place task, the robotic gripper can be attached to the an ABB
robotic arm (6 DOF ABB, IRB120) by means of a 3D printed adaptor as
shown in FIG. 37. The robotic gripper can further be controlled by
means of four solenoid valves (VQ110U-5M) and can be actuated by
four digital outputs of a robot control system. ABB RAPID
programming language can be utilized to control both robot and its
soft gripper robotic device. The ABB RAPID code used to both
control the solenoid valves and the ABB robot arm includes:
TABLE-US-00002 " MODULE Soft Robot PERS tooldata
Extruder:=[TRUE,[[0,0,190],[1,0,0,0]],[0.25,[0,0,1],[1,0,0,0],0,0,0]];
PERS wobjdata
wobj_plate:=[FALSE,TRUE,'''',[[300,0,0],[1,0,0,0]],[[0,0,0],[1,0,0,0]]];
CONST robtarget target:= [[28, 40,
200],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]]; VAR num i:=1;
VAR num j:=2; VAR num k; VAR num s; PROC main( ) i:=1; TPErase;
MoveL
[[0,100,80],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extrud-
er\WObj:=w obj_plate; SetDO DO10_1,0; SetDO DO10_2,1;!open WaitTime
2.5; !first obj MoveL
[[0,100,10],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extrud-
er\WObj:=w obj_plate; SetDO DO10_2,0; SetDO DO10_1,1;!keep waittime
2.5; MoveL
[[0,100,150],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extru-
der\WObj:= wobj_plate; MoveL
[[0,300,150],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extru-
der\WObj:= wobj_plate; MoveL
[[0,300,110],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extru-
der\WObj:= wobj_plate; WaitTime 0.5; SetDO DO10_1,0; SetDO
DO10_2,1;!drop WaitTime 1; MoveL
[[0,300,150],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extru-
der\WObj:= wobj_plate; !2nd obj MoveL
[[0,30,80],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extrude-
r\WObj:=wo bj_plate; SetDO DO10_2,0; SetDO DO10_1,1;!close WaitTime
2; MoveL
[[0,30,10],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extrude-
r\WObj:=wo bj_plate; WaitTime 0.5; SetDO DO10_1,0; SetDO
DO10_2,1;!keep WaitTime 2.5; MoveL
[[0,30,80],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extrude-
r\WObj:=wo bj_plate; MoveL
[[0,200,150],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extru-
der\WObj:= wobj_plate; MoveL
[[0,200,30],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extrud-
er\WObj:=w obj_plate; WaitTime 0.5; SetDO DO10_2,0; SetDO
DO10_1,1;!drop WaitTime 1; MoveL
[[0,200,150],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extru-
der\WObj:= wobj_plate; MoveL
[[0,100,150],[0,1,0,0],[0,0,0,0],[9E9,9E9,9E9,9E9,9E9,9E9]],v50,fine,Extru-
der\WObj:= wobj_plate; endproc ENDMODULE
[0198] In one embodiment, the pneumatic system consists of a LHL
3-way latching solenoid valve, a mini compressor (SN 191852),
Arduino Micro microcontroller and a 9V battery as shown in FIG. 38
shows the actuation system.
[0199] FIG. 39 shows characterization of bending displacement of
soft robotic device type I under different pressure inputs.
[0200] FIG. 40 shows characterization of bending displacement of
soft robotic device type II under different pressure inputs.
[0201] FIG. 41 shows characterization of twisting angle of rotary
device for different input pressures.
[0202] Valvular heart disease including valve stenosis or
regurgitation is a big health concern in modern societies.
According to American Heart Association, more than 200 000
semilunar and about 70 000 atrioventricular valve replacements are
performed annually in USA. It is known that risk factor of heart
valve disease increases with age. Thus, heart valve disease will be
an important concern for rapid aging countries such as USA. While,
surgical valve replacement is not recommended for all patients,
transcatheter heart valve replacement is an alternative treatment
that has been received great attention among researchers recently.
Although this therapy has been relatively established for
replacement of aortic valve, it is not well developed for other
heart valves such as mitral or tricuspid valves. The existing
metallic stent valves cannot efficiently conform to the complex
geometry of mitral/tricuspid valves, resulting in paravalvular leak
and insufficient anchoring. To tackle this problem, the synthetic
heart valves can be made of soft materials such as polymers and
elastomers. Recent invention by Direct Flow Medical (DFM) provides
an inflatable, non-metallic, fully retrievable, and repositionable
percutaneous aortic valve, which may lead to safer implantation of
trans-catheter aortic valve. In one embodiment, the soft robotic
device disclosed herein can be a heart valve, which is an
inflatable unstented prosthetic heart valve and can be deployed to
all four naturally-existing heart valves (tricuspid, pulmonic,
mitral, and aortic valves). As shown in FIG. 42A, when the heat
valve is in an actuated conformation, it is closed and allows low
or no flow though. However, when the heart valve is in an
unactuated conformation it is open and allows flow though. In an
embodiment, the heart valve includes a high-pressure balloon, a
low-pressure balloon and soft arms. FIG. 42B depicts change in
pressure over time, with highest pressure when the heart valve is
closed and lowest pressure when it is open. FIG. 42C shows changes
in pressure as flow rate increases. In another embodiment the heart
valve consists of any one of the three aforementioned components or
any combination and plurality of the three aforementioned
components. In an embodiment of the heart valve embodiment, the
high-pressure balloon can be a patterned low-thickness balloon
which functions as the backbone of the valve, the low-pressure
balloon can be a plane low thickness soft balloon which completely
conforms to the geometry of the valve annulus and eliminates any
paravalvular leaks and finally the soft arms can bend and anchor to
the valve annulus. The subject receiving the heart valve can be a
human, non-human primate or any subject having one or more
naturally existing heart valves. In an embodiment of the heart
valve embodiment, a thermoplastic bonding method can be used to
construct the heart valve by integrating the layers and the frame
of the valve at a single step as depicted in FIGS. 43A-43E. The
thermoplastic bonding method includes cutting a water-soluble film
into a pattern as illustrated in FIG. 43A, heat-pressing the film
between polyurethane films as illustrated in FIG. 43B, cutting
seams to a desired length as illustrated in FIG. 43C, and bending
the obtained patterned balloon into a cylindrical shape,
overlapping and attaching the short edges (e.g., via a binding
clip) as illustrated in FIG. 43D. The frame can then be put inside
an oven, dissolving the water-soluble film, and the frame can be
inflated with polymer or other suitable substance such as a liquid
or a gas, as illustrated in FIG. 43E. In another embodiment a laser
welding method can be used to construct the heart valve.
[0203] In one embodiment, the soft robotic device can be an
inflatable soft stent, referred to as stent hereafter. In an
embodiment, the stent is ultra-thin, conformable and made of
hemo-compatible and biocompatible polyurethane material. In an
embodiment of the stent embodiment, a thermoplastic bonding method
can be used to construct the stent by integrating the layers and
the frame of the stent at a single step as depicted in FIGS.
43A-43E for the heart valve embodiment of a soft robotic device.
FIGS. 43A-43E describe the thermoplastic bonding method using a
valve frame as an example, however, in another embodiment the
method can be applied in the construction of a stent frame or any
other soft robotic device. In another embodiment a laser welding
method can be used to construct the stent. In an embodiment, the
stent is utilized in medical procedures such as percutaneous heart
valve replacement. In another embodiment, the stent is relevant in
maintaining pressure or supporting blood vessels, canals, or ducts
to prevent collapse or re-narrowing of a vessel, aid in healing or
to relieve an obstruction. In one embodiment, the stent may be
pre-coated with a drug such as a drug, which interrupts the
re-narrowing of a blood vessel. In one embodiment, the stem can be
constructed from a polymer, which over time dissolves in a
patient's body.
[0204] An inflatable polyurethane stent is shown in its low-volume
conformation in FIG. 44A, it its deflated conformation in FIG. 44B,
in its inflated conformation in FIG. 44C, and in its inflated
conformation connected to an inflating source in FIG. 44D. In an
embodiment, the stent is 70 .mu.m thick. In another embodiment, the
stent thickness can be more or less than 70 .mu.m. In an
embodiment, the stent is constructed from polyurethane. In another
embodiment, the stent can be made of any suitable polymer, which is
biocompatible and can withstand the heating and cooling processes
involved in soft robotic device construction.
[0205] In one embodiment of the stent embodiment, the stent can be
generated by using a flat plain balloon, bending the balloon to
form a cylindrical shape, and gluing along the short edges as
illustrated in FIGS. 45A and 45B. The flat plain balloon can also
include a pattern to increase flexibility. One example of such a
pattern is a honeycomb pattern as seen in FIGS. 45A-45F. FIG. 45C
shows the stent in its low-volume conformation. FIG. 45D shows the
stent in its deflated conformation. FIG. 45E shows the stent in its
inflated conformation with an inflation source attached. FIG. 45F
shows the stent in its inflated conformation. Other suitable
patterns can also be used to generate a stent. The size and shape
of these patterns can change the radial and axial stiffness of the
stent.
[0206] In an embodiment the stent has a diameter of 26 mm and is
constructed using a heat press method. In another embodiment the
stent diameter may be larger or smaller than 26 mm depending on the
size of the vessel, which needs to be supported. A different method
or combination of methods of construction can also be utilized in
the construction of the stent, for example the laser welding
method. As illustrated in FIG. 46A, the stent can be fixed to a
support stand using a hanging mechanism. The stent can then be
inflated inside a pig aorta while the aorta is attached to a
weight. In an embodiment, the stent can lift a mass of up to 350 gr
(50 gr is the mass of aorta plus metal clip) at a pressure of 21
psi as shown in FIG. 46B. In another embodiment, the stent can lift
a mass greater than 350 g at pressure levels higher or lower than
21 psi. In one embodiment of the stent, the entirety of the valve
is enshrouded with PET fabric in order to reinforce the stent upon
inflation and avoid bursting at high pressure. Furthermore, the
stent surface can be modified to enhance friction forces between
the aorta and the stent. For example, micropatterning can improve
surface friction. In an embodiment, the stent is 70 .mu.m
thick.
[0207] FIGS. 47A-47D show views of different patterns for the
stent. Size and burst pressures for the patterns shown in FIGS.
47A-47D are presented in the table below
TABLE-US-00003 Burst Distance b/w Length of Pattern Thickness
Diameter pressure centers Channels # (mm) (mm) (Psi) (mm) (mm) 1
1.71 25.78 73 5 2 2 2.03 27.01 70 6 3 3 2.74 26.73 45 7 4 4 3.79
23.63 57 8 5
[0208] FIGS. 48A-48D show views of different patterns for the
stent. Size and burst pressures for the patterns shown in FIGS.
48A-48D are presented in the table below:
TABLE-US-00004 Burst Distance b/w Length of Pattern Thickness
Diameter pressure centers Channels # (mm) (mm) (Psi) (mm) (mm) 1
0.95 25.45 49 5 2 2 1.87 25.45 57 6 3 3 2.81 27.08 44 7 4 4 3.72
27.13 30 8 5
[0209] FIGS. 49A-49D show views of different patterns for the
stent. Size and burst pressures for the patterns shown in FIGS.
49A-49D are presented in the table below:
TABLE-US-00005 Burst Distance b/w Length of Pattern Thickness
Diameter Pressure centers channels # (mm) (mm) (psi) (mm) (mm) 1
0.10 24.6 5 5 2 2 1.81 24.93 8 6 3 3 2.80 27.53 5 7 4 4 2.91 26.61
5 8 5
[0210] FIG. 50A shows a set of realistic annulus shapes. These
shapes can be used to show conformability of the stent. FIG. 50B
shows a graph depicting the maximum pull-out for a stent vs.
applied pressure. Sizing of the actuator also may alter the
graph.
[0211] FIGS. 51A-51F show a series of graphs depicting pressure vs.
time.
[0212] FIG. 52 shows two objects coupled together.
[0213] In some embodiments heat can be used to repair small defects
such as delamination or rupture of a soft robotic device.
Thermoplastic-based soft robotic devices can be repaired by hot
pressing the device again. Heat can be applied over the entire
device or in a small region of the device.
[0214] In some embodiments, individual soft robotic devices can be
constructed and then combined to form a more complex, sophisticated
soft machine. These sophisticated soft machines can be made by
combining individual devices by applying heat to join the
devices.
[0215] In some embodiments, the pneumatic network can be a hot
embossed pneumatic network. A replica mold of the pneumatic network
can be provided to imprint a space for the pneumatic network in a
heat softened thermoplastic layer. The thermoplastic sheet retains
the imprint of the embossed pneumatic network. The replica mold can
be made in any suitable dimensions by conventional means, such as
lithographic techniques, laser techniques or 3D printing or any
other conventional methods.
[0216] In one aspect, parts or all of the components of a soft
robotic device may be made of thermoplastic materials such as a
thermoplastic polyurethane ("TPU"). TPUs become liquid-like when
heated above a critical temperature, for example, above 60.degree.
C., or above 170.degree. C., and become solid-like and retain shape
after cool down. The cooled plastics can range from stiff to
flexible. TPUs are formed by the reaction of: (1) diisocyanates
with short-chain diols (so-called chain extenders) and (2)
diisocyanates with long-chain diols. There is an unlimited number
of possible combinations producible by varying the structure and/or
molecular weight of the three reaction compounds. This allows for
an enormous variety of TPUs with diverse physical properties. Thus,
it is possible to select the appropriate TPUs having the
appropriate elasticity for either the pneumatic network or a
stiffer layer.
[0217] Non-limiting example embodiments include:
[0218] Embodiment 1: A method of patterning an object, comprising:
providing a three-dimensional (3D) object; wrapping the 3D object
in the flexible stamp having a micropattern on its surface;
inserting the 3D object and the flexible stamp into a vacuum bag;
applying vacuum to the 3D object and the flexible stamp within the
vacuum bag; and transferring the micropattern of the flexible stamp
to a surface of the 3D object.
[0219] Embodiment 2: Embodiment 1, further comprising:
micropatterning a rigid material via photolithography; and
fabricating the flexible stamp having the micropattern on its
surface using the micropatterned rigid material.
[0220] Embodiment 3: Embodiment 2, further comprising fabricating a
flexible stamp by: inverting the micropatterned rigid material to
form a soft template having the micropattern on its surface;
coating the soft template with an elastomeric material; curing the
elastomeric material to form the flexible stamp; and peeling the
flexible stamp off of the soft template.
[0221] Embodiment 4: Embodiment 3, wherein the soft template
comprises silicone.
[0222] Embodiment 5: Embodiment 3, further comprising applying a
treatment to a surface of the soft template.
[0223] Embodiment 6: Embodiment 5, wherein the surface treatment
comprises trichloro perfluoro silane.
[0224] Embodiment 7: Embodiment 1, wherein the flexible stamp
comprises an elastomeric film.
[0225] Embodiment 8: Embodiment 7, wherein the flexible stamp has a
thickness between 20 and 500 microns.
[0226] Embodiment 9: Embodiment 1, wherein the micropattern has a
thickness between one microns and 40 microns.
[0227] Embodiment 10: Embodiment 1, wherein the 3D object is formed
from at least one of silicone, nitinol alloy, and polyurethane.
[0228] Embodiment 11: Embodiment 1, further comprising treating a
surface of the 3D object to promote adhesion of the flexible stamp
to the 3D object.
[0229] Embodiment 12: A micropatterned object formed by performing
steps comprising: providing a three-dimensional (3D) object;
wrapping the 3D object in a flexible stamp having a micropattern on
its surface; inserting the 3D object and the flexible stamp into a
vacuum bag; applying vacuum to the 3D object and the flexible stamp
within the vacuum bag; and transferring the micropattern of the
flexible stamp to a surface of the 3D object.
[0230] Embodiment 13. A method of manufacturing an implantable
device, the method comprising: positioning a first portion of an
inflatable balloon over a first portion of a sacrificial core;
positioning a second portion of the inflatable balloon over a
second portion of the sacrificial core such that the second portion
of the inflatable balloon at least partially overlaps the first
portion of the inflatable balloon; applying vacuum to the first
portion of the inflatable balloon and the second portion of the
inflatable balloon via a vacuum bag assembly; applying heat to the
first portion of the inflatable balloon and the second portion of
the inflatable balloon to form a thermoplastic bond between the
first portion of the inflatable balloon and the second portion of
the inflatable balloon; and dissolving the sacrificial core.
[0231] Embodiment 14: Embodiment 13, further comprising: wrapping
the third portion of the inflatable balloon and the fourth portion
of the inflatable balloon in a micropatterned stamp prior to
applying the vacuum and the heat to the third portion of the
inflatable balloon and the fourth portion of the inflatable balloon
to impart micropatterned features on at least a portion of the
surface of the inflatable balloon.
[0232] Embodiment 15: Embodiment 14, further comprising:
micropatterning a silicon wafer via photolithography; inverting the
micropatterned silicon wafer to form a master template; spin
coating the master template with an elastomeric material; curing
the elastomeric material to form the micropatterned stamp; and
peeling the micropatterned stamp off of the master template.
[0233] Embodiment 16: Embodiment 13, further comprising: pressure
forming a first film on a lower portion of a three-dimensional (3D)
mold to form the first portion of the inflatable balloon; and
pressure forming a second film on an upper portion of the 3D mold
to form the second portion of the inflatable balloon.
[0234] Embodiment 17: Embodiment 16, further comprising: dissolving
dry pellets of a resin material; and spin coating the dissolved
resin on a flat template to form at least one of the first film and
the second film.
[0235] Embodiment 18: Embodiment 17, wherein the resin material
comprises polyurethane.
[0236] Embodiment 19: Embodiment 16, wherein at least one of the
first film and the second film has a thickness between 30 microns
and 40 microns.
[0237] Embodiment 20: Embodiment 13, further comprising:
constructing a 3D mold of a septum using an additive manufacturing
technique; inverting the 3D mold on a silicone mold; filling the
silicone mold with dry resin pellets; applying heat and vacuum to
the silicone mold and the dry resin pellets to form the septum;
removing the septum from the silicone mold; and inserting the
septum into a hole in the sacrificial core.
[0238] Embodiment 21: Embodiment 20, wherein dissolving the
sacrificial core further comprises: puncturing the septum; and
coupling the inflatable balloon to a perfusion system; and
circulating water through an interior of the inflatable balloon via
the perfusion system to dissolve the sacrificial core.
[0239] Embodiment 22: Embodiment 13, further comprising: wrapping
an elastomeric string around the first portion of the inflatable
balloon and the second portion of the inflatable balloon prior to
applying heat to the first portion of the inflatable balloon and
the second portion of the inflatable balloon.
[0240] Embodiment 23: Embodiment 13, further comprising:
constructing a 3D mold of the sacrificial core using an additive
manufacturing technique; inverting the 3D mold on a silicone mold;
introducing a slurry into the silicone mold; applying heat and
vacuum to the silicone mold to cause the slurry to form the
sacrificial core; and removing the sacrificial core from the
silicone mold.
[0241] Embodiment 24: An implantable device formed by performing
steps comprising: positioning a first portion of an inflatable
balloon over a lower portion of a sacrificial core; positioning a
second portion of the inflatable balloon over an upper portion of
the sacrificial core such that the second portion of the inflatable
balloon at least partially overlaps the first portion of the
inflatable balloon; applying vacuum to the first portion of the
inflatable balloon and the second portion of the inflatable balloon
via a vacuum bag assembly; applying heat to the first portion of
the inflatable balloon and the second portion of the inflatable
balloon to form a thermoplastic bond between the first portion of
the inflatable balloon and the second portion of the inflatable
balloon; and dissolving the sacrificial core.
[0242] Embodiment 25: A soft robotic device comprising: a first
layer bonded to a second layer, wherein at least one layer is
comprised of an extensible thermoplastic material; at least one
layer comprises a pneumatic network; and wherein an initial
conformation of the soft robotic device is a low-volume
conformation or a zero-volume configuration.
[0243] Embodiment 26: Embodiment 25, wherein the pneumatic network
is in contact with a pressurizing source such that the pressurizing
source facilitates transition of the soft robot device from a
low-volume or zero-volume conformation to an extended or actuated
conformation via pressurizing the pneumatic network.
[0244] Embodiment 27: Embodiment 26, wherein the pneumatic network
comprises a plurality of channels arranged in a pattern such that,
upon pressurization by the pressurizing source, the soft robotic
device undergoes at least two types of actuation.
[0245] Embodiment 28: Embodiment 25, wherein the thermoplastic
material comprises a polyurethane or silicone, or ant extensible
polymer.
[0246] Embodiment 29: Embodiment 25, wherein the soft robotic
device is a heart valve.
[0247] Embodiment 30: Embodiment 25, wherein the soft robotic
device is a stent.
[0248] Embodiment 31: Embodiment 25, wherein the soft robotic
device is an in-plane or out-of-plane bending device.
[0249] Embodiment 32: Embodiment 25, wherein the soft robotic
device is a rotary device, an axial rotary device or a bi-axial
rotary device.
[0250] Embodiment 33: Embodiment 25, wherein the soft robotic
device is a gripping device.
[0251] Embodiment 34: Embodiment 25, wherein the soft robotic
device is a robotic swimmer.
[0252] Embodiment 35: Embodiment 25, wherein the soft robotic
device is substantially planar in the initial conformation.
[0253] Embodiment 36: Embodiment 25, wherein the soft robotic
device is rolled in the initial conformation.
[0254] Embodiment 37: A method for constructing the soft robotic
device of Embodiment 25 comprising: providing a first layer and a
second layer; applying heat and/or pressure to the first and second
layers to bond the layers; and sealing first layer and second
layers together using a laser welding technique such that a pattern
is obtained.
[0255] Embodiment 38: A method for constructing the soft robotic
device of Embodiment 25 comprising: providing a film layer; cutting
a film layer pattern from the film layer; providing a first layer
and a second layer; combining the first and second layers with the
film layer pattern such that the first layer is disposed on a first
side, the second layer is disposed on a second side and the film
layer pattern is disposed in between the first and second layers;
applying heat and/or pressure to the first and second layers with
film layer pattern disposed in between first and second layers to
thermally bond the first and second layers; discarding the film
layer pattern such that seams are created on first and/or second
layers; and cutting along the seams on first and/or second layers
such that a pattern is obtained.
[0256] Embodiment 39: Embodiment 38, wherein the film layer
comprises a water-soluble film.
[0257] Embodiment 40: Embodiment 38, wherein the film layer
comprises a material with higher transition temperature than first
and/or second thermoplastic layers.
[0258] Embodiment 41: Embodiment 38, wherein the first and second
layers form a first actuator, the method further comprising
laminating the first actuator to a second actuator.
[0259] As used herein, the singular terms "a," "an," and "the" may
include plural referents unless the context clearly dictates
otherwise.
[0260] As used herein, relative terms, such as "above," "below,"
"up," "left," "right," "down," "top," "bottom," "vertical,"
"horizontal," "side," "higher," "lower," "upper," "over," "under,"
"inner," "interior," "outer," "exterior," "front," "back,"
"upwardly," "lower," "downwardly," "vertical," "vertically,"
"lateral," "laterally" and the like refer to an orientation of a
set of components with respect to one another; this orientation is
in accordance with the drawings, but is not required during
manufacturing or use.
[0261] As used herein, the terms "connect," "connected," and
"connection" refer to an operational coupling or linking. Connected
components can be directly or indirectly coupled to one another,
for example, through another set of components.
[0262] As used herein, the terms "approximately," "substantially,"
"substantial" and "about" are used to describe and account for
small variations. When used in conjunction with an event or
circumstance, the terms can refer to instances in which the event
or circumstance occurs precisely as well as instances in which the
event or circumstance occurs to a close approximation. For example,
when used in conjunction with a numerical value, the terms can
refer to a range of variation less than or equal to .+-.10% of that
numerical value, such as less than or equal to .+-.5%, less than or
equal to .+-.4%, less than or equal to .+-.3%, less than or equal
to .+-.2%, less than or equal to .+-.1%, less than or equal to
.+-.0.5%, less than or equal to .+-.0.1%, or less than or equal to
.+-.0.05%. For example, two numerical values can be deemed to be
"substantially" the same if a difference between the values is less
than or equal to .+-.10% of an average of the values, such as less
than or equal to .+-.5%, less than or equal to .+-.4%, less than or
equal to .+-.3%, less than or equal to .+-.2%, less than or equal
to .+-.1%, less than or equal to .+-.0.5%, less than or equal to
.+-.0.1%, or less than or equal to .+-.0.05%.
[0263] Additionally, amounts, ratios, and other numerical values
are sometimes presented herein in a range format. It is to be
understood that such range format is used for convenience and
brevity and should be understood flexibly to include numerical
values explicitly specified as limits of a range, but also to
include all individual numerical values or sub-ranges encompassed
within that range as if each numerical value and sub-range is
explicitly specified.
[0264] While the present disclosure has been described and
illustrated with reference to specific embodiments and
implementations thereof, these descriptions and illustrations do
not limit the present disclosure. It should be understood by those
skilled in the art that various changes may be made and equivalents
may be substituted without departing from the true spirit and scope
of the present disclosure as defined by the appended claims. The
illustrations may not be necessarily drawn to scale. There may be
distinctions between the artistic renditions in the present
disclosure and the actual apparatus due to manufacturing processes
and tolerances. There may be other embodiments and implementations
of the present disclosure, which are not specifically illustrated.
The specification and drawings are to be regarded as illustrative
rather than restrictive. Modifications may be made to adapt a
particular situation, material, composition of matter, technique,
or process to the objective, spirit and scope of the present
disclosure. All such modifications are intended to be within the
scope of the claims appended hereto. While the techniques disclosed
herein have been described with reference to particular operations
performed in a particular order, it will be understood that these
operations may be combined, sub-divided, or re-ordered to form an
equivalent technique without departing from the teachings of the
present disclosure. Accordingly, unless specifically indicated
herein, the order and grouping of the operations are not
limitations of the present disclosure.
* * * * *