U.S. patent application number 16/624997 was filed with the patent office on 2020-07-23 for hot melt electrospinning.
The applicant listed for this patent is Avectas Limited. Invention is credited to Shane Finnegan, Gillian Hendy, Michael Maguire.
Application Number | 20200232121 16/624997 |
Document ID | / |
Family ID | 63407479 |
Filed Date | 2020-07-23 |
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United States Patent
Application |
20200232121 |
Kind Code |
A1 |
Finnegan; Shane ; et
al. |
July 23, 2020 |
HOT MELT ELECTROSPINNING
Abstract
Systems, devices, and methods for electro spinning are provided.
For example, a system includes a collector including load sensors
attached thereto, the collector configured to receive an extruded
polymer; and an electro spinning melt head assembly positioned
above the collector and configured to extrude the polymer. The
electro spinning melt head assembly and/or the collector is
configured to move. The melt head assembly includes a syringe
assembly and at least one heating element configured to supply heat
to the syringe assembly. The syringe assembly includes: a syringe
including a passage extending from a proximal end, the passage
configured to receive the polymer, and a nozzle configured to allow
polymer to pass therethrough.
Inventors: |
Finnegan; Shane; (Dublin,
IE) ; Hendy; Gillian; (Dublin, IE) ; Maguire;
Michael; (Dublin, IE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Avectas Limited |
Dublin |
|
IE |
|
|
Family ID: |
63407479 |
Appl. No.: |
16/624997 |
Filed: |
June 22, 2018 |
PCT Filed: |
June 22, 2018 |
PCT NO: |
PCT/IB2018/000764 |
371 Date: |
December 20, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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62524119 |
Jun 23, 2017 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D01D 5/0076 20130101;
D01D 5/084 20130101; D01D 5/0023 20130101 |
International
Class: |
D01D 5/00 20060101
D01D005/00; D01D 5/084 20060101 D01D005/084 |
Claims
1. A system, comprising: a collector including load sensors
attached thereto, the collector configured to receive an extruded
polymer; and an electrospinning melt head assembly positioned above
the collector and configured to extrude the polymer, wherein the
electrospinning melt head assembly and/or the collector is
configured to move, the melt head assembly including a syringe
assembly and at least one heating element configured to supply heat
to the syringe assembly, the syringe assembly comprising: a syringe
including a passage extending from a proximal end, the passage
configured to receive the polymer, and a nozzle configured to allow
polymer to pass therethrough.
2. The system of claim 1, the syringe assembly further comprising:
a plunger sized and shaped to be slidably received within the
passage such that distal motion of the plunger causes extrusion of
the polymer; wherein the system further comprises a plunger drive
system configured to supply a mechanical force to actuate the
plunger.
3. The system of claim 2, further comprising: an imaging system
configured to monitor extrusion of the polymer; and a probe
configured to measure a strength of an electric field between the
nozzle and the collector.
4. The system of claim 3, further comprising a control and
processing system configured to receive signals from the plunger
drive system, the imaging system, the load sensors, and the probe,
and to control the position of the electrospinning melt head
assembly, the force applied to the plunger, a voltage of the
collector, and a rate of extrusion of the polymer.
5. The system of claim 4, wherein the rate of extrusion is
controlled to follow a rectified sinusoidal profile.
6. The system of claim 4, wherein the rate of extrusion is between
0.1 gram/hour and 10 gram/hour.
7. The system of claim 6, wherein the rate of extrusion is 0.1
gram/hour, 0.2 gram/hour, 0.3 gram/hour, 0.4 gram/hour, 0.5
gram/hour, 0.6 gram/hour, 0.7 gram/hour, 0.8 gram/hour, 0.9
gram/hour, 1.0 gram/hour, 2.0 gram/hour, 3.0 gram/hour, 4.0
gram/hour, 5.0 gram/hour, 6.0 gram/hour, 7.0 gram/hour, 8.0
gram/hour, 9.0 gram/hour, or 10.0 gram/hour.
8. The system of claim 4, wherein the voltage of the collector is
between 0 and 20 kV, 1 kV, 2 kV, 5 kV, 10 kV, 15 kV, 20 kV, 25 kV,
30 kV, or 40 kV.
9. The system of claim 4, further comprising a voltage source
providing a maximum current to the collector of 0.01 mA, 0.1 mA,
0.18 mA, 0.2 mA, 0.3 mA, 0.6 mA, 1.0 mA, 10 mA, or 100 mA.
10. The system of claim 1, further comprising: a drive system
including a pump configured to supply a pressure inside the syringe
via a gas.
11. The system of claim 1, further including a support assembly
that retains the electrospinning melt head assembly or the
collector.
12. An electrospinning melt head assembly, comprising: a syringe
assembly including, a nozzle, a plunger including at least one
sealing element disposed on an outer surface thereof, a first
passage extending from a first opening in a proximal end of the
syringe assembly, the passage being sized and shaped to slidably
receive the plunger such that the at least one sealing element on
the plunger forms a seal with a wall that defines the first
passage, a second opening in a distal end, the second opening being
fluidly coupled to the first passage, the second opening being
sized and shaped to releasably receive the a portion of the nozzle
therein; at least one heating element configured to supply heat to
the syringe assembly.
13. The assembly of claim 12, further comprising a heater assembly
that retains the at least one heating element, the heater assembly
having a second passage extending from a proximal end thereof, the
second passage sized and shaped to receive the at least a portion
syringe assembly.
14. The assembly of claim 13, wherein the at least one heating
element encircles the second passage.
15. The assembly of claim 13, wherein the heating element is
positioned within a lower half of the heater assembly.
16. The assembly of claim 13, further comprising an insulation
sleeve, the insulation sleeve having a third passage configured to
receive the syringe assembly and the at least one heating
element.
17. A method comprising: applying power to a heating element to
generate heat to transfer to a polymer and melt the polymer within
a syringe; measuring a temperature associated with the polymer;
applying a voltage to a collector to generate an electric field
across a gap between the collector and a nozzle that is releasably
coupled to the syringe; moving the nozzle and/or the collector to
pass the nozzle over a portion of the collector at least one time;
and applying force to a proximal end of a plunger that is slidably
disposed within the syringe to force the plunger toward the nozzle,
thereby forcing a portion of the polymer out of the nozzle and into
the electric field such that it creates a polymer stream extending
from the nozzle, wherein the polymer stream cools and forms fibers
during travel from the nozzle to the collector.
18. The method of claim 17, further comprising adjusting a size of
the gap with every pass of the nozzle over a given point on the
collector.
19. The method of claim 17, further comprising moving the nozzle
and/or collector based on an excursion profile to create small
bends in the polymer stream.
20. The method of claim 0, wherein the excursion profile includes a
rectified sinusoidal profile.
21. The method of claim 17, further comprising using load sensors
to determine a rate of polymer extrusion from the nozzle.
22. The method of claim 17, further comprising using an imaging
system in conjunction with machine vision software to determine a
rate of polymer extrusion from the nozzle.
23. The method of claim 17, wherein air pressure creates the force
at the proximal end of the plunger.
24. The method of claim 0, further comprising reducing the air
pressure sufficiently to draw the plunger away from the nozzle to
stop, or reduce, flow of polymer from the nozzle.
25. The method of claim 17, further comprising measuring a strength
of the electric field.
26. The method of claim 25, further comprising adjusting the
voltage of the collector based on the measured strength of the
electric field.
27. The method of claim 25, further comprising adjusting a size of
the gap between the nozzle and the collector based on the measure
strength of the electric field.
28. A system comprising: a collector including load sensors
attached thereto, the collector configured to receive an extruded
polymer; an electrospinning melt head assembly positioned above the
collector and configured to extrude the polymer, wherein the
electrospinning melt head assembly and/or the collector is
configured to move in at least one of X, Y, and Z directions, the
melt head assembly including a syringe assembly and at least one
heating element configured to supply heat to the syringe assembly,
the syringe assembly comprising: a syringe including a passage
extending from a proximal end, the passage being configured to
receive the polymer, a nozzle configured to allow polymer to pass
therethrough; a drive system configured to supply a pressure inside
the syringe; an imaging system configured to monitor extrusion of
the polymer; and a probe configured to measure a strength of an
electric field between the nozzle and the collector.
29. The system of claim 28, further comprising a control and
processing system configured to receive signals from the drive
system, the imaging system, the load sensors, and the probe, and to
control the position of the electrospinning melt head assembly, the
pressure supplied to the syringe, a voltage of the collector, and a
rate of extrusion of the polymer.
30. The system of claim 28, further including a support assembly
that retains the electrospinning melt head assembly or the
collector.
31. An electrospinning melt head assembly, comprising: a syringe
assembly including a nozzle, a first passage extending from a first
opening in a proximal end of the syringe assembly, a second opening
in a distal end, the second opening being fluidly coupled to the
first passage, the second opening being sized and shaped to
releasably receive the a portion of the nozzle therein; at least
one heating element configured to supply heat to the syringe
assembly.
32. The assembly of claim 31, further comprising a heater assembly
that retains the at least one heating element, the heater assembly
including a second passage extending from a proximal end thereof,
the second passage sized and shaped to receive the at least a
portion syringe assembly.
33. The assembly of claim 32, wherein the at least one heating
element encircles the second passage.
34. The assembly of claim 32, wherein the heating element is
positioned within a lower half of the heater assembly.
35. The assembly of claim 32, further comprising an insulation
sleeve, the insulation sleeve including a third passage configured
to receive the syringe assembly and the at least one heating
element.
36. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. Provisional
Application No. 62/524,119 filed on Jun. 23, 2017, the disclosure
of which is hereby expressly incorporated herein by reference in
its entirety.
FIELD
[0002] The subject matter described herein relates to
electrospinning technology that provides reliable fiber output and
improved control.
BACKGROUND
[0003] Electrospinning can include a method of producing fibers
that utilizes electrical potential to draw liquid polymer threads
across a gap between a conductive source emitter and a conductive
collector, or counter electrode. When a sufficiently high voltage
is applied to a liquid droplet, the body of the liquid can become
charged, and electrostatic repulsion can counteract surface tension
and the droplet can be stretched from the emitter. At a critical
point, as the droplet extends from the emitter toward the counter
electrode, a stream of liquid can erupt from the droplet. The
geometry of the extended droplet from which the stream erupts is
known as a Taylor cone. If molecular cohesion of the liquid is
sufficiently high, stream breakup can be avoided and a charged
liquid jet can be formed. During travel from the emitter to the
collector, the stream can dry. As the stream dries, and/or cools,
the mode of current flow can change from ohmic to convective as
charge migrates to the surface of the forming fiber. While
traveling toward the collector, the stream can be moved by a
"whipping" process to create small bends in the fiber, which can
cause the fiber to thin and lengthen, until it is deposited onto
the collector. The thinning and elongation as a result of the
whipping process can lead to the formation of uniform fibers with
nanometer scale diameters.
[0004] Electrospinning research has been focused towards the
fabrication of nanofibers. The majority of this research involves
the use of solution electrospinning and there has been less
investigation into melt electrospinning since this method most
commonly produces fibers larger than 1 .mu.m. In solution
electrospinning, the jet can thin by an order of magnitude solely
due to the evaporation of solvent. On the other hand, by using high
melt viscosity (.eta..sub.melt) and non-conductive polymer melts
(typically with electrical conductivity less than 10-10 S/m), the
absence of a solvent greatly reduces surface charge density
(.sigma..sub.q) and therefore dampens the bending instabilities.
When the temperature of the electrified jet is below the glass
transition temperature (T.sub.g) of the polymer, rapid
solidification of the molten jet further suppresses whipping; since
greater disturbance forces are required to overcome the surface
tension. The initial region of the electrified molten jet has often
a considerable volume and movement from the midline is reduced. The
suppression of bending instabilities considerably reduces the
degree of stretching the melt electrospinning jet encounters before
it solidifies. With the additional lack of thinning from solvent
evaporation, melt electrospinning has typically been characterized
by larger diameter fibers than from solution.
[0005] Through careful process design, optimization and control,
sub-micron fibers can be obtained in melt electrospinning. Similar
to in melt extrusion systems, this can be accomplished by control
of the extensional viscosity and solidification of the filament via
the thermal environment. However since melt electrospinning is a
further convoluted problem, electric field and charge transfer
effects must be considered in addition to the heat transfer effects
on momentum and mass conservation, viscoelastic properties, and, in
some cases, in-flight crystallization. By making additional
material modifications prior to processing, fiber diameters
approaching true nanoscale magnitudes can be produced using polymer
melts: rather than delivering the polymer in a solution, including
additives to increase the electrical conductivity of the polymer
melt is another strategy to increase the charge density on the melt
jet, thereby inducing a greater degree of stretching on the jet
during flight.
SUMMARY
[0006] The current subject matter can include an electrospinning
melt assembly that monitors and controls a temperature of a
polymer, reduces heat fluctuation in a polymer to achieving uniform
melting of the polymer, measures deposited material during an
experimental run using load sensors on the collector would allow
the user to monitor the rate of extrusion, and uses a rectified
sinusoidal excursion profile during extrusion can provide smoother
linear excursions and hence better deposited fiber structures. In
addition, the current subject matter can include active measurement
and feedback of an electric field between an emitter and a
collector of the electrospinning melt assembly from either current
or charge sensors that can allow the applied voltage to be
controlled, thereby allowing an electric field density to be
maintained.
[0007] In an aspect, a system includes a collector including load
sensors attached thereto, the collector configured to receive an
extruded polymer; and an electrospinning melt head assembly
positioned above the collector and configured to extrude the
polymer. The electrospinning melt head assembly and the collector
are configured to move relative to one another (e.g., the collector
can move and the melt head assembly can be stationary, the melt
head assembly can move and the collector can be stationary, or both
the collector and the melt head assembly can move). The melt head
assembly includes a syringe assembly and at least one heating
element configured to supply heat to the syringe assembly. The
syringe assembly includes: a syringe including a passage extending
from a proximal end, the passage configured to receive the polymer,
and a nozzle configured to allow polymer to pass therethrough.
[0008] One or more of the following features can be included in any
feasible combination. For example, the syringe assembly can include
a plunger sized and shaped to be slidably received within the
passage such that distal motion of the plunger causes extrusion of
the polymer. The system can further include a plunger drive system
configured to supply a mechanical force to actuate the plunger. The
system can include an imaging system configured to monitor
extrusion of the polymer; and a probe configured to measure a
strength of an electric field between the nozzle and the collector.
The system can further include a control and processing system
configured to receive signals from the plunger drive system, the
imaging system, the load sensors, and the probe, and to control the
position of the electrospinning melt head assembly, the force
applied to the plunger, a voltage of the collector, and a rate of
extrusion of the polymer.
[0009] The system can further include a plunger drive system
configured to supply a pressure inside the syringe. The system can
further include a support assembly that retains the electrospinning
melt head assembly.
[0010] The rate of extrusion can be controlled to follow a
rectified sinusoidal profile. In some implementations, the rate of
extrusion is between 0.1 gram/hour and 10 gram/hour. For example,
the rate of extrusion can be 0.1 gram/hour, 0.2 gram/hour, 0.3
gram/hour, 0.4 gram/hour, 0.5 gram/hour, 0.6 gram/hour, 0.7
gram/hour, 0.8 gram/hour, 0.9 gram/hour, 1.0 gram/hour, 2.0
gram/hour, 3.0 gram/hour, 4.0 gram/hour, 5.0 gram/hour, 6.0
gram/hour, 7.0 gram/hour, 8.0 gram/hour, 9.0 gram/hour, or 10.0
gram/hour. The voltage of the collector can be between 0 and 20 kV,
1 kV, 2 kV, 5 kV, 10 kV, 15 kV, 20 kV, 25 kV, 30 kV, or 40 kV. A
voltage source can be included and can provide a maximum current to
the collector of 0.01 mA, 0.1 mA, 0.18 mA, 0.2 mA, 0.3 mA, 0.6 mA,
1.0 mA, 10 mA, or 100 mA. The system can include a drive system,
which can include a plunger or can be without a plunger and
operate, e.g., utilizing gas. For example, the system can include a
drive system including a pump configured to supply a pressure
inside the syringe via a gas.
[0011] The melt head assembly and/or the collector can be
configured to move in one or more of three directions, e.g., x, y,
z directions. In some implementations, the melt head assembly
and/or collector can move in more than the x, y, z directions. For
example, the melt head assembly and/or collector can move in any
specified coordinate system such as polar, spherical, or
cylindrical coordinates. Further, in some implementations, the melt
head assembly and/or collector can move in 2, 3, 4, 5, 6, 7, 8, 9,
10, 11, 12, and/or more directions. In some implementations, the x
and y directions are separated by 90 degrees, and the z direction
is separated by 90 degrees from a plane formed in the x and y
directions. In some implementations, the collector moves such that
the motion of the melt head assembly is relative to the collector.
In some implementations, the collector can include a cylindrical
shape and rotate around a central access. In some implementations,
the collector can include a flat plate.
[0012] In another aspect, an electrospinning system includes a
collector, an electrospinning melt head assembly, a plunger drive
system, an imaging system, and a probe. The collector includes load
sensors attached thereto. The collector is configured to receive an
extruded polymer. The electrospinning melt head assembly is
positioned above the collector and is configured to extrude the
polymer. The electrospinning melt head assembly is configured to
move in X, Y, and Z directions. The melt head assembly includes a
syringe assembly and at least one heating element configured to
supply heat to the syringe assembly. The syringe assembly includes
a syringe, a plunger, and a nozzle. The syringe includes a passage
extending from a proximal end. The passage is configured to receive
the polymer. The plunger is sized and shaped to be slidably
received within the passage such that distal motion of the plunger
causes extrusion of the polymer. The nozzle is configured to allow
polymer to pass therethrough. The plunger drive system is
configured to supply a mechanical force to actuate the plunger. The
imaging system is configured to monitor extrusion of the polymer.
The probe is configured to measure a strength of an electric field
between the nozzle and the collector.
[0013] One or more of the following features can be included in any
feasible combination. For example, a control and processing system
can be included and can be configured to receive signals from the
plunger drive system, the imaging system, the load sensors, and the
probe, and to control the position of the electrospinning melt head
assembly, the force applied to the plunger, a voltage of the
collector, and a rate of extrusion of the polymer.
[0014] A support assembly can be included that retains the
electrospinning melt head assembly.
[0015] In another aspect, an electrospinning melt head assembly
includes a syringe assembly including a nozzle, a plunger including
at least one sealing element disposed on an outer surface thereof,
a first passage extending from a first opening in a proximal end of
the syringe assembly, the passage being sized and shaped to
slidably receive the plunger such that the at least one sealing
element on the plunger forms a seal with a wall that defines the
first passage, a second opening in a distal end, the second opening
being fluidly coupled to the first passage, the second opening
being sized and shaped to releasably receive a portion of the
nozzle therein; and at least one heating element configured to
supply heat to the syringe assembly.
[0016] One or more of the following features can be included in any
feasible combination. For example, a heater assembly can be
included that retains the at least one heating element, the heater
assembly including a second passage extending from a proximal end
thereof, the second passage sized and shaped to receive the at
least a portion syringe assembly. The at least one heating element
can encircle the second passage. The heating element can be
positioned within a lower half of the heater assembly. An
insulation sleeve can be included. The insulation sleeve can
include a third passage configured to receive the syringe assembly
and the at least one heating element.
[0017] In yet another aspect, power is applied to a heating element
to generate heat to transfer to a polymer. A temperature associated
with the polymer is measured. The polymer is melted within a
syringe. A voltage is applied to a collector to generate an
electric field across a gap between the collector and a nozzle that
is releasably coupled to the syringe. The nozzle is passed over a
portion of the collector at least one time. Force is applied to a
proximal end of a plunger that is slidably disposed within the
syringe to force the plunger toward the nozzle, thereby forcing a
portion of the polymer out of the nozzle and into the electric
field such that it creates a polymer stream extending from the
nozzle. The polymer stream cools and forms fibers during travel
from the nozzle to the collector.
[0018] One or more of the following features can be included in any
feasible combination. A size of the gap can be adjusted with every
pass of the nozzle over a given point on the collector. The nozzle
can be moved based on an excursion profile to create small bends in
the polymer stream. The excursion profile can include a rectified
sinusoidal profile. Load sensors can be used to determine a rate of
polymer extrusion from the nozzle. An imaging system can be used in
conjunction with machine vision software to determine a rate of
polymer extrusion from the nozzle. Air pressure can create the
force at the proximal end of the plunger. The air pressure can be
reduced sufficiently to draw the plunger away from the nozzle to
stop, or reduce, flow of polymer from the nozzle. A strength of the
electric field can be measured. The voltage of the collector can be
adjusted based on the measured strength of the electric field. A
size of the gap between the nozzle and the collector can be
adjusted based on the measure strength of the electric field.
[0019] In yet another aspect, a system includes a collector
including load sensors attached thereto, the collector configured
to receive an extruded polymer; an electrospinning melt head
assembly positioned above the collector and configured to extrude
the polymer, wherein the electrospinning melt head assembly is
configured to move in X, Y, and Z directions, the melt head
assembly including a syringe assembly and at least one heating
element configured to supply heat to the syringe assembly, the
syringe assembly comprising: a syringe including a passage
extending from a proximal end, the passage being configured to
receive the polymer, a nozzle configured to allow polymer to pass
therethrough; a plunger drive system configured to supply a
pressure inside the syringe; an imaging system configured to
monitor extrusion of the polymer; and a probe configured to measure
a strength of an electric field between the nozzle and the
collector.
[0020] One or more of the following features can be included in any
feasible combination. The system can further include a control and
processing system configured to receive signals from the plunger
drive system, the imaging system, the load sensors, and the probe,
and to control the position of the electrospinning melt head
assembly, the pressure supplied to the syringe, a voltage of the
collector, and a rate of extrusion of the polymer. The system can
further include a support assembly that retains the electrospinning
melt head assembly.
[0021] In yet another aspect, an electrospinning melt head assembly
includes a syringe assembly including a nozzle, a first passage
extending from a first opening in a proximal end of the syringe
assembly, a second opening in a distal end, the second opening
being fluidly coupled to the first passage, the second opening
being sized and shaped to releasably receive a portion of the
nozzle therein; at least one heating element configured to supply
heat to the syringe assembly.
[0022] One or more of the following features can be included in any
feasible combination. For example, the assembly can further include
a heater assembly that retains the at least one heating element,
the heater assembly including a second passage extending from a
proximal end thereof, the second passage sized and shaped to
receive the at least a portion syringe assembly. The at least one
heating element can encircle the second passage. The heating
element can be positioned within a lower half of the heater
assembly. The assembly can further include an insulation sleeve,
the insulation sleeve including a third passage configured to
receive the syringe assembly and the at least one heating
element.
DESCRIPTION OF DRAWINGS
[0023] FIG. 1 is an exploded view of an exemplary embodiment of an
electrospinning melt head assembly;
[0024] FIG. 2 is an enlarged view of a syringe assembly of the
electrospinning melt head assembly of FIG. 1;
[0025] FIG. 3 is a cross-sectional view of a nozzle of the syringe
assembly of FIG. 2;
[0026] FIG. 4 is an enlarged view of a heater assembly of the
electrospinning melt assembly shown in FIG. 1;
[0027] FIG. 5 is a perspective view of another embodiment of a
heater assembly;
[0028] FIG. 6 is a side cross-sectional view of the heater assembly
of FIG. 5;
[0029] FIG. 7 is an a perspective view of the syringe assembly of
FIG. 2 and the heater assembly of FIG. 5;
[0030] FIG. 8 is a bottom perspective view of the syringe assembly
of FIG. 2 positioned within the heater assembly of FIG. 5;
[0031] FIG. 9 is a perspective exploded view of a support
assembly;
[0032] FIG. 10 is an enlarged perspective view of an upper cover
and a heater assembly support plate of the support assembly of FIG.
9;
[0033] FIG. 11 is a cross-sectional view of the electrospinning
melt head assembly of FIG. 1 within the support assembly of FIG.
9;
[0034] FIG. 12 is a diagram of an embodiment of an electrospinning
system;
[0035] FIG. 13 is a diagram of signal communication between a
control and processing system and various other components of the
electrospinning system of FIG. 12;
[0036] FIG. 14a is an excursion profile;
[0037] FIG. 14b is another example of an excursion profile;
[0038] FIG. 15 is a perspective view of a cap of the syringe
assembly of FIG. 2
[0039] FIG. 16 is a bottom view of the cap of FIG. 15;
[0040] FIG. 17 is perspective view of a syringe cap of the
electrospinning melt head assembly of FIG. 1;
[0041] FIG. 18 is a top view of the syringe cap of FIG. 17;
[0042] FIG. 19 is a side view of the syringe cap of FIG. 17;
[0043] FIG. 20A-F illustrate some aspects of an example
implementation of the current subject matter; and
[0044] FIG. 21 is a table that details certain technical
specifications of an embodiment of an electrospinning system that
can be similar to the electrospinning system of FIG. 12.
DETAILED DESCRIPTION
[0045] Certain exemplary embodiments will now be described to
provide an overall understanding of the principles of the
structure, function, manufacture, and use of the systems, devices,
and methods disclosed herein. One or more examples of these
embodiments are illustrated in the accompanying drawings. Those
skilled in the art will understand that the systems, devices, and
methods specifically described herein and illustrated in the
accompanying drawings are non-limiting exemplary embodiments and
that the scope of the present invention is defined solely by the
claims. The features illustrated or described in connection with
one exemplary embodiment may be combined with the features of other
embodiments. Such modifications and variations are intended to be
included within the scope of the present subject matter. Further,
in the present disclosure, like-named components of the embodiments
generally have similar features, and thus within a particular
embodiment each feature of each like-named component is not
necessarily fully elaborated upon.
[0046] Electrospinning can include a method of producing polymer
fibers that utilizes electrical potential to draw liquid polymer
threads across a gap between a conductive source emitter, such as a
nozzle, and a conductive collector, or counter electrode. This
process can be used to produce scaffolds, which cells and tissue
can be seeded and grown on. One way this process can be improved is
by reducing heat fluctuation in the polymer to achieve uniform
melting of the polymer and hence uniform extrusion. Uniform
extrusion can improve control of properties of the scaffold such
as, e.g., porosity. With greater control of the properties of the
scaffold, a more repeatable scaffold construction can be achieved,
and the properties of the scaffold can be optimized to tissue
growth. Additionally uniform geometries can provide ideal matching
between cell sizes and scaffolds, provide the potential for
mechanical cues from the uniform geometry e.g., enhanced nerve
guides, provide predictable (by model) mechanical characteristics
of scaffolds in dynamic settings e.g., aorta, and provide
independence of fiber diameter and pore size in the scaffold. The
temperature of the melt head can be monitored and tracked over time
to determine the stability of the system. The tracking can be
performed using a heat sensor such as a PT100 resistance
temperature device (RTD) and an analog I/O device to measure and
control the process. ("Pt" is the symbol for platinum, "100" for
the resistance in ohms at 0.degree. C.). Additionally, tracking can
be performed using (1) data logging with a computer and a
thermocouple and/or RTD and (2) an error term e in a
proportional-integral-derivative (PID) controller. The error term e
can be a difference between a set point and a measured temperature,
and can be integrated over the fabrication time of a scaffold
(minutes to hours). Stability can be effected by (1) an auto-tune
function on the PID controller but can also be determined by (2)
tuning/stability methods such as Ziegler-Nichols tuning. The
stability can ensure that the emitter reaches and maintains an
ideal temperature with minimal overshoot.
[0047] Another way the electrospinning process can be improved is
by measuring deposited material during an experimental run using
load sensors on the collector to allow the user to monitor the rate
of extrusion. For example, a single load cell capable of measuring
micro-newton forces as a function of time f(t) can be employed. The
load cell can be placed between movable stage and a counter
electrode. The load cell can have sufficient dynamic range to
receive the weight of the platform and still measure small forces.
A signal from the load cell can be low pass filtered to derive a
signal changing slowly with increasing force due a mass of
deposited material. Such a signal can also be used to modulate the
material deposition rate. Any rapid changes in f(t) may signal
erroneous or non-uniform deposition and can signal an alarm state
in software. Additionally, using a rectified sinusoidal excursion
profile during extrusion can provide smoother linear excursions and
hence better deposited fiber structures. As another example, active
measurement and feedback of the electrical field between the
emitter and the collector from either current or charge sensors can
allow the applied voltage to be controlled, thereby allowing the
electrical field density to be maintained.
[0048] In some implementations, feedback to increase the separation
distance with every pass can be monitored and controlled and
combined with any control of the electric field to ensure
consistency of the process theatre with every pass.
[0049] FIG. 1 shows an exploded view of an exemplary embodiment of
an electrospinning melt head assembly 100. The melt head assembly
100 can include a syringe assembly 110, a heater assembly 140, a
high-temperature insulation sleeve 170, and syringe cap 190. The
syringe assembly 110 can function to retain and controllably
deposit a polymer onto a substrate. The syringe assembly 110 can be
received within the heater assembly 140, which can function to heat
the polymer to a desired temperature, and the heater assembly 140
can be inserted into the insulation sleeve 170. The melt head cover
can be positioned over a proximal end of the syringe assembly 110
and the heater assembly 140 to provide a layer of thermal
insulation while allowing access to the syringe assembly 110 and
the heater assembly 140. The specific components of the
electrospinning melt head assembly 100 will be discussed in more
detail below.
[0050] FIG. 2 shows an enlarged view of the syringe assembly 110 of
FIG. 1. The syringe assembly 110 can include a syringe 112, a
plunger 114, a cap 116, and a nozzle 118. As shown in FIGS. 1-2,
the syringe 112 can have a substantially cylindrical geometry and
can include a first opening 120a on a proximal end 112a, a second
opening (not shown) on a distal end 112b, and a passage 120
extending therebetween, where the passage can extend along a
central axis A2. The passage 120 that extends from the proximal end
112a to the distal end 112b can receive a polymer to be heated and
extruded, deposited, or spun, onto a substrate. The opening 120a in
the proximal end can receive the plunger 114, which can have at
least one or more sealing elements 113 such as, e.g., O-rings,
which can form a seal with a wall of the passage 120 of the syringe
112. In some embodiments, the plunger can have two sealing elements
113. In some embodiments, the plunger can be made of stainless
steel. The plunger can translate proximally and distally within the
passage 120 of the syringe 112 to control extrusion of the polymer.
In practice, there are a number of ways that the position of the
plunger 114 can be controlled. For example, the position of the
plunger 114 can be altered by applying positive air pressure to a
proximal end 114a of the plunger 114. Alternatively, a shaft can be
coupled to the opening 115 in the proximal end 114a of the plunger,
and force can be applied to the plunger 114 via the shaft.
Adjusting the position of the plunger 114 using air pressure can be
beneficial because it can simplify construction and reduce costs.
Air or some other appropriate gas pressure can be applied directly
to the molten polymer to extrude it through the nozzle. The method
of operation is discussed in more detail below.
[0051] The cap 116 can function to couple the nozzle 118 to the
syringe 112 and to provide access to the passageway of the syringe
112 through the distal end 112b. In the illustrated example, the
cap 116 has a substantially cylindrically body, and includes a
cylindrical mating feature 122 that extends in a proximal
direction. The mating feature 122 can allow the cap 116 to be
releasably coupled to the syringe 112 via the second opening on the
distal end 112b of the syringe 112. The cap 116 can be coupled to
the syringe 112 in any number of ways. For example, the mating
feature 122 can have threads that can mate with threads in the
second opening of the syringe 112. Alternatively, the mating
feature 122 and the second opening can be coupled via, e.g.,
friction fit. In some embodiments, the mating feature 122 can
include seals 124 disposed on an outer surface thereof. The mating
feature 122 can be received within the second opening of the
syringe 112, and the seals 124 can form a seal between the mating
feature 122 and the passage 120 of the syringe 112. In some
embodiments, the seals can include O-rings that can be made of
perfluoro-elastomers FFKM. Additionally, the mating feature 122 can
have a curved face 117 that can make with a distal end 114b of the
plunger.
[0052] As shown in FIGS. 1-2, the syringe 112 and the cap 116 can
include bores 126a, 126b, and bores 126c, 126d, all of which can be
threaded, and temperature measurement channels 128a, 128b. The
bores 126a, 126b can allow the syringe 112 to be coupled to the cap
116. FIGS. 15-16 show enlarged views of the cap 116. As shown in
FIGS. 2, 15, and 16, bores 126b, 126d can be larger than bores
126a, 126c. This can help to ensure that the cap 116 and syringe
112 are properly aligned during assembly. Bores 126a can align with
bores 126b, and bore 126c can align with bore 126d, and the syringe
112 can be coupled to the cap 116 via coupling elements such as,
e.g., screws or bolts, that can extend through the bores 126a,
126b, 126c, 126d. The temperature measurement channels 128a, 128b
can receive a temperature measurement sensor such as, e.g., a
thermocouple, PT100 RTD, and the like that can extend through the
syringe 112 and into the cap 116 to monitor the temperature of the
cap 116 as close to the nozzle 118 as possible. Although not
illustrated, the syringe 112 and cap 116 can include multiple
temperature measurement channels that can receive temperature
measurement sensors. Including more than one channel can allow
multiple temperatures to be taken at various positions along the
length of the syringe 112 and cap 116. In an exemplary embodiment,
the syringe 112 and cap 116 can be made from stainless steel.
Stainless steel can provide a good combination of corrosion
resistance, thermal conductivity, and machinability. However, the
syringe 112 and cap 116 can be made of any corrosion resistant
material, such as e.g., titanium, nickel, or any other material
suitable for the described purpose. In some embodiments, the cap
116 can be integral with the syringe 112.
[0053] As shown in FIG. 3, the nozzle 118 can include a central
passage 130 that extends through a proximal mating portion 131, and
a distal extrusion portion 132. The central passage 130 can have a
first portion 135 with a first diameter, and a second portion 137
having a second diameter. The first portion 135 can extend from an
inlet 130a on a proximal end 118a of the proximal mating portion,
and the second portion 137 can lead to an outlet 130b on a distal
end 118b of the distal extrusion portion 132. The distal spray
portion 132 can include an internal inwardly tapering surface 132a,
which can create a transition region that can couple the first
portion 135 of the passage 130 to the second portion 137 of the
passage 130. The internal inwardly tapering surface 132a can result
in the outlet 130b of the nozzle 118 having a smaller diameter than
the inlet 130a of the nozzle 118. In some embodiments, a coating of
a conductive material can cover part of the extrusion portion 132
of the nozzle 118. The coating can act as a high voltage electrode
when connected to an appropriate high voltage source.
[0054] In some implementations, a high voltage source can be
included that applies a voltage between 0 and 20 kV. In some
implementations, the voltage source can provide a voltage of 1 kV,
2 kV, 5 kV, 10 kV, 15 kV, 20 kV, 25 kV, 30 kV, 40 kV, or more. The
voltage supply can provide voltage resolution 10 V, for example. In
some implementations, the voltage source can provide a maximum
current of 0.18 mA. In some implementations, the voltage source can
provide a maximum current of 0.01 mA, 0.1 mA, 0.2 mA, 0.3 mA, 0.6
mA, 1.0 mA, 10 mA, 100 mA, or more.
[0055] In the illustrated embodiment, the proximal mating portion
131 of the nozzle 118 can include threads that can mate with
threads in an opening 119 (shown in FIG. 16) in the cap 116. In an
exemplary embodiment, the nozzle 118 can be made of a material that
has thermal expansion coefficient that is greater than that of the
cap 116. For example, if the cap 116 is made of a stainless steel,
the nozzle 118 can be made of brass. Therefore, when the melt head
assembly 100 is heated, the nozzle 118 can expand more than the cap
116, which can help form a seal between the threads on the mating
portion 131 of the nozzle and threads in the opening in the cap
116.
[0056] In order to provide heat to the polymer that is within the
syringe 112, the syringe assembly 110 can be inserted into the
heater assembly 140. FIG. 4 shows an enlarged view of the heater
assembly 140 shown in FIG. 1. The heater assembly 140 can include
heating elements 154, a heating member 142, or body, which can be
in the form of, e.g., a cylindrical sleeve, as well as a heater cap
144, and a mounting flange 146. The heating member 142, heater cap
144, and mounting flange 146 can all have substantially cylindrical
geometries. The mounting flange 146 can include sleeve coupling
bores 146a, heater bores 146b, support coupling bores 146c, and a
central bore 146d. The sleeve coupling bores 146a can align with
coupling bores 143a on a proximal end 142a of the heating member
142, and can allow the mounting flange 146 to be coupled to the
heating member 142 using a coupling element such as, e.g., a screw
or bolt. The support coupling bores 146c can function to allow the
heater assembly 140 to be coupled to a support frame, which is
discussed in more detail below.
[0057] As shown in FIG. 4, the heating member 142 can have a
substantially cylindrical geometry and can include a first opening
148a on a proximal end 142a, a second opening (not shown) on a
distal end 142b, and a passage 148 extending therebetween. The
heating member 142 can include the coupling bores 143a as well as
heater bores 143b on the proximal end 142a. As described above, the
coupling bores 143a on the heating member 142 can align with
coupling bores 146a on the mounting flange 146, and can allow the
heating member 142 and mounting flange 146 to be coupled using
coupling elements such as screw or bolts. The heater bores 143b can
extend through the length of the heating member 142 and can align
with heater bores 146b of the mounting flange 146 on the proximal
end 142a of the heating member 142, and with heater bores 145b of
the cap 144 on the distal end 142b of the heating member 142.
[0058] The heater cap 144 can include the heater bores 145b as well
as coupling bores 145a. The heater cap 144 can have a recessed
region 150 extending distally from an opening 150a in a proximal
end 144a, and can also include a bore 152 extending through the
distal end 144b of the cap 144. The central bore 146d, passage 148,
recessed region 150, and bore 152 can share a central axis A3 and
can align such that the syringe assembly 110 can be received within
the heater assembly 140. The recessed region 150 of the cap 144 can
receive, and seat, a distal portion of the syringe assembly 110,
and the bore 152 can allow the nozzle 118 to extend through the
distal end 144b of the heater cap 144.
[0059] Heating elements 154 such as, e.g., cartridge heaters, can
be used to provide heat to the syringe assembly 112. In some
embodiments, the heating elements 154 can be 200 W cartridge
heaters. In other embodiments, the heating elements can generate
greater than 200 W of heat, or less than 200 W of heat. The heating
elements 154 can be inserted through heater bores 146b and 143b,
and can extend into heater bores 145b in the heater cap 144. The
heating elements 154 can heat the mounting flange 146, the heating
member 142, and the heater cap 144, which can in turn heat the
syringe assembly 110 and the polymer that can be within the syringe
112. In some embodiments, the heating elements 154 can heat the
heater assembly 140 up to temperature of approximately 250.degree.
C.
[0060] The heating member 142, mounting flange 146, and cap 144 can
be made of any material suitable for the described purpose.
However, in an exemplary embodiment, the heating member 142,
mounting flange 146, and cap 144 can be made of aluminum. Aluminum
has a relatively high thermal conductivity, which can result in a
more uniform temperature distribution since heat from the heating
elements 154 can conduct well through each of the parts of the
heater assembly 140.
[0061] The syringe assembly 110 and heater assembly 140 can be
insulated using, e.g., the insulation sleeve 170, to minimize heat
loss and improve temperature control. Referring back to FIG. 1, the
insulation sleeve 170 can include a passage 172 that can extend
between an opening 172a in a proximal end 170a of the insulation
sleeve 170 and an opening (not shown) in a distal end 170b of the
insulation sleeve 170. The syringe assembly 110 and the heater
assembly 140 can be inserted into the passage 172 of the insulation
sleeve 170. The insulation sleeve 170 can be made of any insulating
material that can withstand the maximum temperature of the heating
elements 154. In some embodiments, the insulating sleeve can be
made of calcium silicate. The insulation sleeve 170 and heating
elements 154 can form a concentrated heating zone. This
concentrated heating zone focuses the heat in a volume of the
syringe where, in operation, polymer is loaded.
[0062] In order to provide insulation at the proximal end of the
syringe 112, the syringe cap 190 can be positioned over the
proximal end 112a of the syringe and/or the mounting flange 146.
The syringe cap 190 have a substantially cylindrical geometry, and
can include an array of bore holes 192 that can extend from a
proximal end 190a syringe cap 190 to a distal end 190b of the
syringe cap 190. In some embodiments, a portion of the cap 190 can
extend into the passage 120 of the syringe 112 such that it forms a
seal with the wall that defines the passage 120. In some
embodiments, the syringe cap 190 can be made of, for example,
DuroBest.RTM. 280 (agk), Polyether ether ketone (PEEK) or
IGLIDUR.RTM. (IGUS INC., East Providence R.I. 02914). FIGS. 17-19
show various views of the syringe cap 190. The bore holes 192 can
provide access to the syringe assembly 110 and/or the heater
assembly 140. For example, at least one bore hole 196 can provide
access to the temperature measurement channel 128a such that a
temperature sensor 129 can be inserted into temperature measurement
channels 128a, 128b. In some embodiments, the temperature sensor
129 can be a 4 mm PT100 temperature sensor, or a type K
thermocouple. In some embodiments, the syringe cap 190 can include
coupling bores 195a, 195c, which can align with bores 126a, 126c of
the syringe 112 and can allow the syringe cap 190 to be coupled to
the syringe 112 using coupling elements such as, e.g., screws or
bolts. The syringe cap 190 can also include mounting bores 197,
which are discussed more below. A hose fitting can be coupled to an
air inlet port 193 such that gas pressure can be applied the
plunger to force polymer liquid from the nozzle. Alternatively, a
shaft can extend through the inlet port 193 and can be coupled to
the opening 115 in the proximal end 114a of the plunger. The shaft
can then apply mechanical force to the plunger to move it
proximally and/or distally within the passage 120 of the syringe
112. In some implementations, gas can be applied directly to the
molten polymer. In some implementations, a solenoid valve can be
utilized to control the gas pressure, including applying positive
and negative pressure on the plunger. This approach can provide
improved control of the extrusion process.
[0063] In some embodiments, a heater assembly can have a unibody
configuration rather than having multiple components such as those
described with regard to heater assembly 140. The heater assembly
can also have heating elements embedded into it. FIGS. 5-6 show an
example of an embodiment of a heater assembly 240 that has a
unibody configuration and that can have one or more embedded
heating elements 254. Temperature sensors can also be embedded into
the unibody configuration. FIG. 5 shows a perspective view of the
heater assembly 240, and FIG. 6 shows a side cross-sectional view
of the heater assembly 240. The heater assembly 240 can have a body
242 that can have a substantially cylindrical geometry, and it can
include a central passage 248 that can extend from an opening 248a
in a proximal end 240a of the heater assembly 240, toward a distal
end 240b of the heater assembly 240. The proximal end 240a of the
heater assembly 240 can include a flange 246 that can extend
radially outward. The flange 246 can have support coupling bores
246c that can function similarly to support coupling bores 146c.
The distal end 240b of the heater assembly can have a bore 252 that
can receive a nozzle such as nozzle 118 of the syringe assembly
110. In the illustrated embodiment, the central passage 248 and the
bore 252 can share a central axis A4.
[0064] The heater assembly 240 can also include a port 260 having a
radial passage 262 that can extend from an end 260a of the port 260
to the central passage 248. The port 260 can allow wires to be
passed into and out of the passage 248. For example, wires from the
temperature sensor 129 that can monitor the temperature of a
syringe assembly such as syringe assembly 110 can be passed through
the passage 262 of the port 260.
[0065] In the illustrated example, rather than inserting heating
elements into bores of the heater assembly, as described with
regard to heater assembly 140, the heating elements 254 can be
embedded in a concentrated heated region 256 of the body 242 of the
heater assembly 240. In some embodiments, the heated region 256 can
be limited to a lower half, or distal half, of the heater assembly
240. The heating elements 254 can be one or more resistive heaters
that can encircle, or wind around, the passage 248 within the body
242 of the heater assembly 240. The heating elements 254 can
receive power from a power source via a cable 257 that can extend
out of the body 242 of the heater assembly 240. Using a heater
assembly configuration that includes heating elements that wrap
around the passage 248 can provide more uniform heat transfer to
the syringe assembly 110, which can result in the polymer having a
more uniform temperature distribution. Such a configuration can
increase the precision of a control system that can be used to
monitor and maintain the temperature of the syringe assembly 110
and/or the polymer that is within the syringe 112. By creating a
more uniform temperature profile, temperature measurements can be
less sensitive to the exact position of the temperature sensor 129,
which can result in increased accuracy and precision of the
temperature measurement. In some embodiments, the passage 262 of
the port 260 does not extend into the passage 248. In that case,
passage 262 can be used to pass cables that can couple to the
heating elements 254 or temperature sensors within the walls of the
heater assembly. For example, cable 257 can extend from the heating
elements 254, up to passage 262, and out of the heater assembly
240, rather than extending out of the body 242 of the heater
assembly 240.
[0066] FIGS. 7 and 8 show how the syringe assembly 110 can be
received within the heater assembly 240. FIG. 7 shows the syringe
assembly 110 aligned with the opening 248a in the proximal end 240a
of the heater assembly. FIG. 8 shows the syringe assembly 110
positioned within the passage 248 of the heater assembly.
[0067] Regardless of which heater assembly is used, the melt head
assembly 100 can be supported within a support assembly. The
support assembly 300, shown in FIG. 9, can include upper and lower
covers 302, 304, side covers 305, 306, upper and lower support
frames 308, 309 and heater assembly support plate 310.
[0068] The lower cover 304 can generally be in the shape of a
square or rectangular plate. In some embodiments, the lower cover
304 can be made of Polytetrafluoroethylene (PTFE), Polyether ether
ketone (PEEK) and/or another electrically insulating and thermally
resistant material. The lower cover 304 can have a recessed region
312 extending distally from an opening 312a in a proximal surface
304a, and can also include a bore 352 extending from the recessed
region 312 to a distal surface 304b of the cover 304. The lower
cover 304 can also have coupling bores 314a that can extend
distally from the proximal surface 304a of the lower cover 304. The
recessed region 312 can be sized and shaped to receive a distal
portion of the insulation sleeve 170. The bore 352 can generally
align with bore 252 of the heater assembly 240 such that it can
receive the nozzle 118 of the syringe assembly 110.
[0069] As illustrated in FIG. 9, the support assembly 300 can
include upper and lower support frames 308, 309, or structural
ribs. In some embodiments, the upper and lower support frames 308,
309 can be made of aluminum. The support frames 308, 309 can
generally be square or rectangular in shape and can have perimeter
dimensions that can be approximately equal to those of the lower
cover 304. The support frames 308, 309 can have passages 316, 318
that extend from proximal surfaces 308a, 309a to distal surface
308b, 309b of the frames. In the illustrated example, the passages
316, 318 have generally square shapes. However, the passages 316,
318 can have any geometry suitable to receive and retain the melt
head assembly 100. In addition to the passages 316, 318 for
receiving the melt head assembly 100, the support frames 308, 309
can have first sets of coupling bores 320a, 321a, second sets of
coupling bores 320b, 321b, and third sets of coupling bores 320c,
321c.
[0070] In the illustrated example, the side covers 305, 306 include
coupling bores 319b. The coupling bores 319b can align with
coupling bores 320b, 321b of the support frames 308, 309 to allow
the side covers 305, 306 to be coupled to the support frames 308,
309 using, e.g., a screw, bolt, or pin. As shown in FIG. 9, the
support plate 306 can also include larger coupling bores 319c as
well as a passage 322. In some embodiments, passage 322 can be used
to feed power cables to the cartridge heaters 154, or to the
heating elements 254, from an external power supply. These cables
can be managed by the use of trunking and labeling. The cables can
further include inlet filters to improve the electro-magnetic
compatibility (EMC) characteristics of the system and/or prevent
the electrical leakage. The bores 320c, 321c can align with bores
319c on the side cover 306, and they can allow the melt head
assembly 100 and the support assembly 300 to be coupled to a
mounting assembly (not shown) using coupling elements such as,
e.g., screws, bolts, or another spacing mechanism such as spacing
posts, rods, or an adaptor plate. In some embodiments the side
covers 305, 306 can be made of aluminum and can be powder coated
white. Although the side cover 305 is illustrated as a three-sided
piece of folded aluminum, each side of the side cover 305 can be an
individual piece similar to side cover 306.
[0071] FIG. 10 shows an enlarged view of the upper cover 302 and
the heater assembly support plate 310. In some embodiments the
upper cover 302 can be made of aluminum and can be powder coated
white, and the heater support plate 310 can be made of Polyether
ether ketone (PEEK). The heater assembly support plate 310 can also
generally be square or rectangular in shape and can have perimeter
dimensions that can be approximately equal to those of the lower
cover 304. The support plate 310 can have a recessed region 324
extending distally from an opening 324a in a proximal surface 310a,
and can also include a bore 326 extending from the recessed region
324 to a distal surface 310b of the support plate 310. The support
plate 310 can also include coupling bores 328a, and first and
second sets of countersunk coupling bores 330a, 332a. Additionally,
the recessed region can include syringe cap 190 mounting bores 325.
The cap mounting bores 325 can align with the mounting bores 197 on
the syringe cap, which can allow the syringe cap 190 to be coupled
to the heater assembly support plate 310 using coupling elements
such as, screws, bolts, or other coupling elements suitable for the
described purpose
[0072] The upper cover 302 can generally be square or rectangular
in shape, and can include coupling bores 334a that can align with
the coupling bores 328a in the support plate 310, and a central
bore 336 that can align with the opening 324a in the support plate
310.
[0073] The support assembly 300 can be assembled by coupling the
various components using coupling elements such as, e.g., screws,
bolts, and/or pins. The distal end 170b of the insulation sleeve
170 can be positioned in the recessed region 312 of the lower cover
304.
[0074] The distal surface 318a of the lower support frame 309 can
be positioned over the proximal surface 304a of the lower cover 304
such that the coupling bores 320a align with coupling bores 314a.
Coupling elements can be inserted into the coupling bores 314a,
320a to couple the lower support frame 309 to the lower cover
304.
[0075] The heater assembly 240 can be inserted into passage 172 of
the insulation sleeve 170 such that bore 252 of the heater assembly
240 aligns with bore 352 of the lower cover 304. Although not
shown, the insulation sleeve 170 can have a radial bore to allow
the port 260 of the heater assembly 240 to pass therethrough. The
electrospinning melt head assembly 100 and the support assembly 300
can be assembled as follows.
[0076] The syringe assembly 110 can be inserted into the heater
assembly 240. A polymer that can be used for electrospinning can be
inserted into the passage 120 of the syringe 112. The polymer can
be in the form of beads.
[0077] The upper support frame 308 can be coupled to the side
covers 305, 306 using coupling elements that can extend through
some of the coupling bores 319b in the side covers 305, 306 and
into the coupling bores 320b on the upper support frame.
[0078] The upper support frame 308, with the side covers 305, 306
releasably attached thereto, can be positioned over the insulation
sleeve 170 such that the remainder of the coupling bores 319b align
with the coupling bores 321b on the lower support frame 309.
[0079] The larger coupling bores 319c on the side cover 306 can be
releasably attached to the third sets of coupling bores 320c, 321c
on the upper and lower support frames 308, 309.
[0080] The heater support plate 310 can be positioned over the
insulation sleeve 170, heater assembly 240 and syringe assembly
110. The heater support plate 310 can be releasably coupled to the
proximal end 240a of the heater assembly 240 by coupling elements
that can be inserted into countersunk coupling bores 330a on the
heater assembly 240 and into coupling bores 246c on the proximal
end 240a of the heater assembly 240. The heater support plate 310
can also be coupled to the upper support frame 308 via coupling
elements that can be inserted into countersunk coupling bores 332a
and into coupling bores 320a on the upper support 308.
[0081] The distal end 190b of the syringe cap 190 can be placed
into the recessed region 324 of the heater support plate 310.
Although not illustrated, the syringe cap 190 can have sealing
elements that extend around its perimeter that can form a seal with
the recessed region 324.
[0082] The upper cover 302 can be attached to the heater support
plate 310 via coupling elements that can be inserted into coupling
bores 334a in the upper cover 302 and into coupling bores 328a in
the support plate 310.
[0083] If a multicomponent heater assembly, such as heater assembly
140, is used, it can be assembled as described above, and it can be
incorporated into the melt head assembly 100 in the same manner as
the heater assembly 240. FIG. 11 shows a cross-sectional view of
the electrospinning melt head assembly 100, shown in FIG. 1, within
the support assembly 300, illustrated in FIG. 9. As shown in FIG.
11, a portion 190c of the cap 190 can extend into the passage 120
of the syringe 112 such that it forms a seal with the wall that
defines the passage 120.
[0084] FIG. 12 shows a diagram of an embodiment of an
electrospinning system 400. The electrospinning system 400 can
include the electrospinning melt head assembly 100, including the
support assembly 300, a collector assembly 402, an imaging system
404, a plunger drive system 406, a probe 408, and a control and
processing system 410. The melt head assembly 100 can be assembled
and coupled with the support assembly 300 as described above, and
it can be mounted on a mount assembly (not shown) that allows the
melt head assembly to be moved along X, Y, and Z axes.
[0085] As described above, the plunger 114 of the syringe assembly
110 can be driven by applying air pressure to the proximal surface
114a, or by using a rigid mechanical connector such as a rod. The
plunger drive system 406 can deliver air or another mechanical
force to the plunger to create proximal or distal displacement to
expel polymer liquid or to draw it back into the syringe 112. In
some implementations, the plunger drive system 406 can include a
pump. The plunger drive system 406 can send and receive signals to
and from the control and processing system 410 to control the
position of the plunger 114, thereby controlling flow of polymer
from the nozzle 118. In some embodiments, the plunger 114 can be
omitted, thereby the applied air pressure directly expels polymer
liquid or draws it back into the syringe 112. The gas that is
supplied into the syringe 112 is not limited to air, but can also
include any inert gases such as, e.g., nitrogen or argon. In some
implementations, omitting the plunger 114 can be advantageous in
some implementations because in implementations that utilize a
plunger, molten polymer can extrude through the nozzle even when no
driving force is applied. Due to the air tight fit between the
piston and the walls of the melt chamber, any expanded air in the
system during the heating phase may drive molten polymer through
the nozzle as it may not be relieved.
[0086] As polymer is expelled from the nozzle 118, it can be
deposited onto a collector 412 of the collector assembly 402. The
collector assembly 402 can include the collector 412, a base 414,
and one or more load sensors 416 that can be used to determine the
amount of polymer that has been deposited onto the collector 412.
By measuring the amount of polymer that has been deposited onto the
collector, a rate of polymer extrusion from the nozzle 118 can be
determined. In some embodiments, the nozzle 118 can be grounded,
and high voltage power can be supplied to the collector 412 such
that an electric field is created between the collector 412 and the
nozzle 118. In some embodiments, the collector 412 can have a
conductive coating that can allow it to function as an electrode.
In other embodiments, the collector 412 can be conductive.
[0087] In addition to, or as an alternative to, using load sensors
416 to measure the amount of polymer deposited onto the collector
412, the imaging system 404 can be used in conjunction with machine
vision software to determine an extrusion rate of the polymer and
to track the amount of extruded polymer. The imaging system 404 can
have a field of view (FOV) that includes the nozzle 118 and the
collector 412.
[0088] As the polymer threads are deposited onto the collector 412,
in a region sometimes referred to as the boundry, and the polymer
scaffold increases in height, an electric field generated between
the nozzle 118 and the collector 412 can change and/or weaken due
to insulating properties of the polymer. The probe 408 can measure
the electric field between the nozzle 118 and the collector 412.
The probe 408 can be, e.g., a field mill, or an electric field
meter (EFM). Alternatively, or additionally, the probe 408 can
measure charge of the collector 412 and/or the polymer on the
collector. Information about the electric field between the nozzle
118 and the collector 412 can be used to adjust power delivered to,
or voltage of, the collector 412, thereby allowing the electric
field density to be maintained. The information about the electric
field can also be used to adjust the position of the
electrospinning melt head assembly 100 in the Z direction with each
pass, thereby altering the electric field. In some embodiments, the
collector 412 can have a stippled and/or spiked surface, which can
allow for a more consistent electric field density during polymer
deposition. In some embodiments, the stipples and/or spikes can
extend between approximately 1 mm and 2 mm, or less than 10 mm,
from the surface of the collector. The stipples and/or spikes can
be arranged in an array, they can have varying pitch. Regions of
the collector 412 can also have stipples and/or spikes that can
arranged in patterns with varying density. In other words, certain
regions of the collector 412 can have stipples and/or spikes that
can be more closely packed than they are in other regions of the
collector 412.
[0089] The electrospinning process occurs over a short separation
distance between the collector 412 and the nozzle 118. In a similar
fashion to the electric field, as the scaffold increases in height
with every pass, the separation between the collector 412 and the
nozzle 118 can increase as well to retain a consistent deposition
distance between the nozzle 118 and the previously laid fiber of
polymer.
[0090] A position of the nozzle 118 can be monitored, and feedback
can be used to increase the separation distance with every pass.
The nozzle 118 can be monitored and controlled and combined with
any control of the electric field to ensure consistency of the
process theatre with every pass of the nozzle 118 over a given
point on the collector 412.
[0091] FIG. 13 shows a diagram of signal communication between the
control and processing system 410 and various other components of
the electrospinning system 400. As shown in FIG. 13, the control
and processing system 410 can include an image processing module
422, an electric field module 424, a load module 426, a plunger
module 428, a heater module 430, and a collector module 432.
[0092] The heater module 430 can send and receive signals to and
from the temperature senor 129 and the heating elements 254. In
operation, a desired polymer temperature can be selected via the
control and processing system 410. The selected temperature can
correspond to an initial power that can be provided to the heating
elements from a power supply. The temperature of the nozzle 118 can
be measured using the temperature sensor 129 in temperature
measurement channels 128a, 128b of the syringe assembly 110. The
temperature sensor 129 can send temperature signals to the heater
module 430, which can analyze the signals, calculate the
temperature, determine an appropriate action for the heating
elements 254, and send a corresponding heating signal to the to the
heating elements 254. System behavior can be coordinated in
hardware and software developed to signal condition multiple inputs
(e.g., temperature, stage location, and material deposition rate)
and perform computations on the inputs to produce outputs (e.g.,
heater coil power, plunger excursion, electric field potential). In
some embodiments, a resistance temperature detector (RTD) such as a
PT100 RTD can be used to measure the temperature of the nozzle 118.
In that case, the heater module 430 can measure the resistance
across the temperature sensor 129, and correlate that resistance to
a temperature value. In other embodiments, a thermocouple, e.g., a
type-K thermocouple, can be used to measure the temperature of the
nozzle 118. A melting temperature of the polymer can be determined
empirically prior to loading the polymer into the syringe 112. For
example, phase change experiments can be conducted by heating and
melting the polymer and measuring the temperature of the polymer
throughout the heating and melting process. In some embodiments,
the heating signal can come from a power supply of the heater
module. The heater module 430 can include a proportional
integral-derivative (PID) controller and can utilize PID control
with an auto-tuning function to control power that is delivered to
the heating elements 254. The input can be the temperature signal
from the temperature sensor 129, and the output can be the heating
signal. The auto-tuning function can determine a thermal response
of the system over time and can calculate a system parameter to
correctly drive the system. As described above, the temperature
sensor 129 can be an RTD, a thermocouple, or both. If more than one
temperature sensor 129 is implemented, one sensor can be used as a
reference for the PID controller and another sensor can be used for
monitoring the melting temperature of the polymer. Use of a type K
thermocouple can be more dynamic than the PT100 temperature sensor.
This can reduce or prevent overshoot of the polymer as the heater
reaches a desired setpoint quicker and so can be close to a steady
state by the time sufficient conduction occurs. This can include a
gradual heating process compared to some embodiments. In addition,
the use of separate monitor and control temperature probes can
allow for fine temperature adjustment of the melt set point, which
combats natural losses. In some implementations, the PID controller
reference temperature can be built into the heating head such that
it cannot be removed, which reduces the chance of overheating the
system to the point of irreversible damage.
[0093] Once the temperature sensor is outputting a signal
corresponding to the desired temperature of the polymer, the melt
head assembly 100 can be left to heat for a period of time to
ensure that it has reached thermal equilibrium. The polymer that is
not in direct contact with the syringe 112 will melt due to the
thermal conductivity of the loaded polymer. The time taken to melt
all of the polymer will depend on the mass of the polymer and its
thermal conductivity.
[0094] The PID temperature can further include a dual relay control
on the heater power lines, temperature lockouts and internal
alarms/latches to improve the user-safety and/or the performance of
the device.
[0095] When the system has reached thermal equilibrium, the polymer
can be extruded through the nozzle 118. High voltage power can be
supplied to the collector 412 from the collector module 432. The
collector module 432 can also monitor the voltage at the collector
412, and a position of the nozzle 118 in the X, Y, and Z
directions. The plunger module 428 can also deliver a drive signal
to the plunger drive system 406. The plunger drive system 406 can
receive the drive signal and can provide air pressure to space
between the proximal end 114a of the plunger 114 and a distal end
190b of the syringe cap 190 to drive the plunger 114 distally
within the passage 120 of the syringe 112 to force polymer liquid
from the nozzle 118. Alternatively, if the plunger is driven by a
rod, the plunger drive system 406 can apply a force to the rod to
displace the plunger. If the air pressure directly drives the
melted polymer without a plunger, the plunger drive system 406 can
receive the drive signal and can provide air pressure to space
between the proximal end of the melted polymer and the distal end
190b of the syringe cap 190 to force polymer liquid from the
nozzle. The rate of this natural extrusion can be dependent on the
viscosity of the melted polymer. Low viscosity melted polymers can
extrude very fast while high viscosity polymers can extrude very
slowly.
[0096] At a critical point, as a polymer droplet extends from the
nozzle 118 toward the collector, a stream of polymer liquid can
erupt from the droplet. During travel from the nozzle 118 to the
collector 412, the stream can dry. As the stream dries, or cools, a
mode of current flow can change from ohmic to convective as charge
migrates to the surface of the forming fiber. While traveling
toward the collector 412, the collector module 432 can deliver a
motion signal to the mounting assembly (not shown) that retains the
melt head assembly 100 to move the melt head assembly 100 in the
X-Y plane to create small bends in the fiber, which can cause the
fiber to thin and lengthen, until it is deposited onto the
collector. In some implementations, the mounting assembly retains
the collector 412 to move the collector in the X-Y plane to crease
the small bends in the fiber, which can cause the fiber to then and
lengthen, until it is deposited onto the collector 412. The
thinning and elongation as a result of the X-Y motion can lead to
the formation of uniform fibers with nanometer scale diameters. The
X-Y motion of the melt head assembly 100 and/or the collector 412
can be achieved by a XYZ drive system that can be implemented with
various actuation mechanisms such as, e.g., a ball-and-screw drive
system or a linear positioner. When the linear positioner is used,
linear interpolation can be facilitated to maintain a constant
speed during curve operations, with which there is no acceleration
or deceleration during cornering and hence grids with round
features can be deposited. In addition, constant linear speed can
prevent curly melt electrospun fibers.
[0097] In some embodiments, G-code can be used to create polymer
scaffolds at certain porosity and density. In other embodiments,
position table logic can be used to command the motion of the melt
head assembly 100. An excursion profile of linear stages of motion
can be important to creating thin, straight fibers. Extrusion and
deposition of straight fibers can be dependent on the velocity
profile of the linear stages of motion. If the velocity is not
suitably matched to the extrusion rate (the rate of
electrospinning), i.e., the extrusion rate is too fast or too slow,
the deposited fibers can be curly, rather than straight. An
excursion profile 500 can be seen in FIG. 14a. The excursion
profile 500 shows that each pass has a first portion 502 that shows
linear acceleration, a second portion 504 that shows constant
velocity, and a third portion 506 that shows constant linear
deceleration at the end of the pass. This excursion profile 500 is
abrupt in its nature given the short and fast nature of the
excursion. Rather than using the excursion profile 500 shown in
FIG. 14a, an excursion profile 600 that utilizes a rectified
sinusoidal profile 602, as shown in FIG. 14b, can provide smoother
linear excursions and hence better deposited fibers.
[0098] Referring back to FIG. 13, as polymer fibers are deposited
onto the collector 412, the imaging system 404 can monitor the rate
and volume of polymer extrusion from the nozzle 118. The imaging
system 404 can deliver imaging signals to the image processing
module 422. The image processing module 422 can deliver rate
signals to the collector module 432 and the plunger module 428. The
collector module 432 and plunger module 428 can receive the rate
signals and can deliver signals to the collector 412 and to the
plunger drive system 406 to adjust the voltage of the collector 412
and the pressure applied to the plunger 114, respectively. By
adjusting the voltage at the collector 412, the electric field
density can be maintained.
[0099] The load sensors 416 can measure pressure from the weight of
the polymer fibers on the collector 412 and can deliver
corresponding signals to the load module 426. The load module 426
can receive the signals, determine how much polymer is on the
collector 412, as well as the rate of extrusion, and can deliver
corresponding load signals to the collector module 432 and the
plunger module 428. For example, the mass of the polymer on the
collector 412 can be determined by the load sensors 416 and the
load module 426. A volume of polymer can be determined using a
known density, molar mass, and/or molecular weight of the polymer,
in conjunction with measured mass on the collector 412. A rate of
polymer extrusion can be found by determining a change in the
mass/volume of polymer on the collector 412 and dividing by a time
that elapsed between measurements. Load signals can be analog and
can be converted to digital by the load module 426. The collector
module 432 and the plunger module 428 can deliver signals to the
nozzle 118 and to the plunger drive system 406 to adjust the
voltage of the nozzle 118 and the rate of extrusion,
respectively.
[0100] The probe 408 can measure the strength of the electric field
between the nozzle 118 and the collector 412 and can deliver field
signals to the electric field module 424. The field signals can
correspond to the strength of the electric field between the nozzle
118 and the collector 412, and/or the charge of the collector 412.
In some embodiments, the electric field module 424 can include a
micro-ammeter or other charge/current detector. Therefore, the
collector 412 can deliver charge signals to the electric field
module 424. The charge signals can correspond to the charge of the
collector 412. The electric field module 424 can receive the field
signals and charge signals from the probe 408 and collector 412,
respectively, and can deliver a signal to the collector module 432.
The collector module 432 can receive the signal and can adjust the
voltage of the collector 412 or adjust the position of the melt
head assembly 100 in the Z axis, thereby adjusting a gap distance
between the nozzle 118 and the collector 412. The collector module
432 can also deliver a signal to the plunger module 428, which can
deliver a signal to the plunger drive system 406 to adjust the rate
of extrusion.
[0101] The rate of polymer extrusion can also be reduced or stopped
at any point during the extrusion process. For example, of the rate
of polymer extrusion determined to be too high, or if extrusion is
complete, the plunger module 428 can deliver a signal to the
plunger drive system 406 indicating that the plunger 114 should be
retracted. The plunger drive system 406 can create vacuum pressure
behind the plunger 114 to draw it proximally within the passage 120
of the syringe 112, thereby drawing the polymer liquid away from
the nozzle 118. In other words the air pressure applied to the
proximal end of the plunger 114 can be reduced sufficiently to draw
the plunger proximally within the passage 120 to stop, or reduce,
flow of polymer from the nozzle 118.
[0102] In the embodiment of the electrospinning system 400
described above, the nozzle 118 is grounded while a voltage is
applied to the collector 412. However, in some embodiments, a
voltage can be applied to the nozzle 118 and the collector 412 can
be grounded or provided another voltage. Such a configuration can
generate an electric field between the nozzle 118 and the collector
412 that can facilitate polymer extrusion.
[0103] In some embodiments, electric, fluidic and temperature
subsystems can be integrated into a single enclosure. The
subsystems can further include a safety circuitry for improved
user-safety. Moreover, the electric, fluidic and temperature
subsystems can be controlled by a closed-loop control by, e.g., a
programmable logic controller (PLC) over an Ethernet IP protocol.
Using a PLC can reduce the manufacturing assembly time and allow
the user to store operating parameters into memory for repeatable
deployment. Further, by using a PLC, the system can be setup so
that it is operable when all operating parameters are within an
acceptable range. The PLC can also include safety features to
prevent the heater overheating, to control the high voltage module,
and to monitor the system pressure. In addition, the PLC of the
system can have a human-machine interface (HMI) to provide a
standalone operating without requiring a PC to interact with an
operator in regards to operating parameters such as pressure,
temperature, speed, and number of cycles, to provide the operator
with feedback, errors, current program, temperatures, speeds,
pressure values and voltage values.
[0104] FIG. 20A-F illustrate some aspects of an example
implementation of the current subject matter. Melt electrospinning
can be considered as an alternative polymer processing technology
that can enable fabrication of three dimensional scaffolds. Some
implementations can be solvent free and allow the use of polymers
that do not dissolve easily. Some implementations can enable
advances in the field of tissue engineering, where solvent
retention and toxicity can be a concern. Some implementations of
the current subject matter can include a melt electrospinning
instrument capable of melting polymers with melting points up to
250 degrees Celsius. Some implementations can enable melt
electrospinning writing (MEW) through the use of an x-y stage as
the collection platform. FIG. 20A illustrates the interplay between
process and operational parameters for MEW including polymer,
collector, voltage, software, distance, heating element,
translational speed, and flow rate. FIG. 20B illustrates a
schematic diagram of an MEW instrument. FIG. 20C illustrates a
table of polymer, molecular weight, and melting temperature. The
polymers include Polycaprolactone (PCL), Polydioxanone (PDS), poly
lactic-co-glycolic acid (PLGA), Thermoplastic polyurethane (TPU),
and Polystyrene (PS). FIGS. 20D-F illustrate output scaffolds built
using an example MEW system, illustrating morphology, resolution,
and versatility of different structures and materials.
[0105] FIG. 21 shows a table that details certain technical
specifications of an embodiment of an electrospinning system that
can be similar to electrospinning system 400.
[0106] In some implementations, the control system conditions and
buffers signal to a robust industry scheme (0-10 volts). Data
acquisition hardware is employed and values provided to a software
module, which drives outputs through analogue output (e.g., 12 bit
Pulse Width Modulation). Alarms, boundaries, maximum, minimum and
average values can be calculated.
[0107] In some implementations, the melt head assembly can move in
more than the x, y, z directions. For example, the melt head
assembly can move in any specified coordinate system such as polar,
spherical, or cylindrical coordinates. Further, the melt head
assembly can move in 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and/or
more directions. In some implementations, the x and y directions
are separated by 90 degrees, and the z direction is separated by 90
degrees from a plane formed in the x and y directions. In some
implementations, the collector moves such that the motion of the
melt head assembly is relative to the collector. In some
implementations, the collector can also be cylindrical and rotate
around its own central axis
[0108] Other embodiments are within the scope and spirit of the
disclosed subject matter.
[0109] The techniques described herein can be implemented using one
or more modules. As used herein, the term "module" refers to
computing software, firmware, hardware, and/or various combinations
thereof. At a minimum, however, modules are not to be interpreted
as software that is not implemented on hardware, firmware, or
recorded on a non-transitory processor readable recordable storage
medium (i.e., modules are not software per se). Indeed "module" is
to be interpreted to always include at least some physical,
non-transitory hardware such as a part of a processor or computer.
Two different modules can share the same physical hardware (e.g.,
two different modules can use the same processor and network
interface). The modules described herein can be combined,
integrated, separated, and/or duplicated to support various
applications. Also, a function described herein as being performed
at a particular module can be performed at one or more other
modules and/or by one or more other devices instead of or in
addition to the function performed at the particular module.
Further, the modules can be implemented across multiple devices
and/or other components local or remote to one another.
Additionally, the modules can be moved from one device and added to
another device, and/or can be included in both devices.
[0110] One or more aspects or features of the subject matter
described herein can be realized in digital electronic circuitry,
integrated circuitry, specially designed application specific
integrated circuits (ASICs), field programmable gate arrays (FPGAs)
computer hardware, firmware, software, and/or combinations thereof.
These various aspects or features can include implementation in one
or more computer programs that are executable and/or interpretable
on a programmable system including at least one programmable
processor, which can be special or general purpose, coupled to
receive data and instructions from, and to transmit data and
instructions to, a storage system, at least one input device, and
at least one output device. The programmable system or computing
system may include clients and servers. A client and server are
generally remote from each other and typically interact through a
communication network. The relationship of client and server arises
by virtue of computer programs running on the respective computers
and having a client-server relationship to each other.
[0111] These computer programs, which can also be referred to as
programs, software, software applications, applications,
components, or code, include machine instructions for a
programmable processor, and can be implemented in a high-level
procedural language, an object-oriented programming language, a
functional programming language, a logical programming language,
and/or in assembly/machine language. As used herein, the term
"machine-readable medium" refers to any computer program product,
apparatus and/or device, such as for example magnetic discs,
optical disks, memory, and Programmable Logic Devices (PLDs), used
to provide machine instructions and/or data to a programmable
processor, including a machine-readable medium that receives
machine instructions as a machine-readable signal. The term
"machine-readable signal" refers to any signal used to provide
machine instructions and/or data to a programmable processor. The
machine-readable medium can store such machine instructions
non-transitorily, such as for example as would a non-transient
solid-state memory or a magnetic hard drive or any equivalent
storage medium. The machine-readable medium can alternatively or
additionally store such machine instructions in a transient manner,
such as for example as would a processor cache or other random
access memory associated with one or more physical processor
cores.
[0112] To provide for interaction with a user, one or more aspects
or features of the subject matter described herein can be
implemented on a computer having a display device, such as for
example a cathode ray tube (CRT) or a liquid crystal display (LCD)
or a light emitting diode (LED) monitor for displaying information
to the user and a keyboard and a pointing device, such as for
example a mouse or a trackball, by which the user may provide input
to the computer. Other kinds of devices can be used to provide for
interaction with a user as well. For example, feedback provided to
the user can be any form of sensory feedback, such as for example
visual feedback, auditory feedback, or tactile feedback; and input
from the user may be received in any form, including, but not
limited to, acoustic, speech, or tactile input. Other possible
input devices include, but are not limited to, touch screens or
other touch-sensitive devices such as single or multi-point
resistive or capacitive trackpads, voice recognition hardware and
software, optical scanners, optical pointers, digital image capture
devices and associated interpretation software, and the like.
[0113] In the descriptions above and in the claims, phrases such as
"at least one of" or "one or more of" may occur followed by a
conjunctive list of elements or features. The term "and/or" may
also occur in a list of two or more elements or features. Unless
otherwise implicitly or explicitly contradicted by the context in
which it is used, such a phrase is intended to mean any of the
listed elements or features individually or any of the recited
elements or features in combination with any of the other recited
elements or features. For example, the phrases "at least one of A
and B;" "one or more of A and B;" and "A and/or B" are each
intended to mean "A alone, B alone, or A and B together." A similar
interpretation is also intended for lists including three or more
items. For example, the phrases "at least one of A, B, and C;" "one
or more of A, B, and C;" and "A, B, and/or C" are each intended to
mean "A alone, B alone, C alone, A and B together, A and C
together, B and C together, or A and B and C together." In
addition, use of the term "based on," above and in the claims is
intended to mean, "based at least in part on," such that an
unrecited feature or element is also permissible.
[0114] The subject matter described herein can be embodied in
systems, apparatus, methods, and/or articles depending on the
desired configuration. The implementations set forth in the
foregoing description do not represent all implementations
consistent with the subject matter described herein. Instead, they
are merely some examples consistent with aspects related to the
described subject matter. Although a few variations have been
described in detail above, other modifications or additions are
possible. In particular, further features and/or variations can be
provided in addition to those set forth herein. For example, the
implementations described above can be directed to various
combinations and subcombinations of the disclosed features and/or
combinations and subcombinations of several further features
disclosed above. In addition, the logic flows depicted in the
accompanying figures and/or described herein do not necessarily
require the particular order shown, or sequential order, to achieve
desirable results. Other implementations may be within the scope of
the following claims.
* * * * *