U.S. patent application number 09/568615 was filed with the patent office on 2001-12-06 for method for loading shape memory polymer gripper mechanisms.
Invention is credited to Benett, William J., Fitch, Joseph P., Krulevitch, Peter A., Lee, Abraham P., Schumann, Daniel L..
Application Number | 20010047579 09/568615 |
Document ID | / |
Family ID | 25530712 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010047579 |
Kind Code |
A1 |
Lee, Abraham P. ; et
al. |
December 6, 2001 |
Method for loading shape memory polymer gripper mechanisms
Abstract
A method and apparatus for loading deposit material, such as an
embolic coil, into a shape memory polymer (SMP) gripping/release
mechanism. The apparatus enables the application of uniform
pressure to secure a grip by the SMP mechanism on the deposit
material via differential pressure between, for example, vacuum
within the SMP mechanism and hydrostatic water pressure on the
exterior of the SMP mechanism. The SMP tubing material of the
mechanism is heated to above the glass transformation temperature
(Tg) while reshaping, and subsequently cooled to below Tg to freeze
the shape. The heating and/or cooling may, for example, be provided
by the same water applied for pressurization or the heating can be
applied by optical fibers packaged to the SMP mechanism for
directing a laser beam, for example, thereunto. At a point of use,
the deposit material is released from the SMP mechanism by
reheating the SMP material to above the temperature Tg whereby it
returns to its initial shape. The reheating of the SMP material may
be carried out by injecting heated fluid (water) through an
associated catheter or by optical fibers and an associated beam of
laser light, for example.
Inventors: |
Lee, Abraham P.; (Walnut
Creek, CA) ; Benett, William J.; (Livermore, CA)
; Schumann, Daniel L.; (Concord, CA) ; Krulevitch,
Peter A.; (Pleasanton, CA) ; Fitch, Joseph P.;
(Livermore, CA) |
Correspondence
Address: |
L.E. CARNAHAN
ASSISTANT LABORATORY COUNSEL
LAWRENCE LIVERMORE NATIONAL LABORATORY
P.O. BOX 808, L-703
LIVERMORE
CA
24981
US
|
Family ID: |
25530712 |
Appl. No.: |
09/568615 |
Filed: |
May 10, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09568615 |
May 10, 2000 |
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08984624 |
Dec 3, 1997 |
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6240630 |
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Current U.S.
Class: |
29/447 |
Current CPC
Class: |
Y10T 29/49929 20150115;
Y10T 29/53987 20150115; Y10T 29/49865 20150115; A61B 17/221
20130101; A61B 2017/12072 20130101; A61B 2017/12068 20130101; A61B
17/1219 20130101; A61B 2017/1205 20130101; A61B 2017/00867
20130101; A61B 2017/00871 20130101; A61B 2017/00345 20130101; Y10T
29/53439 20150115 |
Class at
Publication: |
29/447 |
International
Class: |
B23P 011/02 |
Goverment Interests
[0001] The United States Government has rights in this invention
pursuant to Contract No. W-7405-ENG48 between the United States
Department of Energy and the University of California for the
operation of Lawrence Livermore National Laboratory.
Claims
The invention claimed is:
1. An apparatus for loading a shape memory polymer gripper/release
mechanism, comprising: means for heating the shape memory polymer
having a configuration; means for applying pressure to the heated
shape memory polymer to cause a change in the configuration of the
shape memory polymer; and means for cooling the shape memory
polymer to maintain the configuration of shape memory polymer
caused by applying pressure thereto.
2. The apparatus of claim 1, wherein the means for applying
pressure includes means for producing a differential pressure on
the shape memory polymer.
3. The apparatus of claim 2, wherein the means for producing
differential pressure including a vacuum and a hydrostatic or
mechanical pressure.
4. The apparatus of claim 3, wherein said shape memory polymer is
of a hollow configuration, and wherein said differential pressure
is applied by means across at least a portion of a wall surface
forming the hollow configuration.
5. The apparatus of claim 4, wherein the differential pressure is
produced between vacuum means and hydrostatic water pressure
means.
6. The apparatus of claim 5, wherein the vacuum means is applied to
an interior of said hollow configuration and said hydrostatic water
pressure means is applied to an exterior of said hollow
configuration.
7. The apparatus of claim 1, wherein said means for applying
pressure includes a plurality of members having means for at least
forming indentations in said shape memory polymer.
8. The apparatus of claim 7, wherein said plurality of members are
moved against a surface of said shape memory polymer by means
forming a differential pressure.
9. The apparatus of claim 1, wherein said means for applying
pressure includes a plurality of flexible members at least forming
spaced seals about said shape memory polymer.
10. The apparatus of claim 9, wherein said spaced seals form an
area about said shape memory polymer into which fluid pressure is
directed to form at least one indentation in said shape memory
polymer.
11. The apparatus of claim 1, wherein said heating means is
selected from the group selected from heated fluid and laser
light.
12. The apparatus of claim 1, wherein said heating means, said
pressure applying means, and said cooling means each include a
quantity of fluid.
13. The apparatus of claim 12, wherein said heating means, pressure
applying means, and said cooling means includes the same fluid.
14. The apparatus of claim 11, wherein said heating means includes
at least one optical fiber for directing laser light onto said
shape memory material.
15. The apparatus of claim 14, wherein said shape memory polymer is
of a tubular configuration and said laser light is directed into an
interior of said tubular configurations.
16. The apparatus of claim 1, wherein said cooling means includes a
quantity of cooled water capable of cooling the heated, pressurized
shape memory material to a temperature below a phase transformation
temperature of said shape memory polymer.
17. A method for loading a shape memory polymer to form a
gripper/release mechanism retaining a deposit material, including:
heating a quantity of shape memory polymer, having at least a
section of a deposit material located therein, to a temperature
above a transformation temperature of the shape memory polymer;
applying differential pressure across the heated shape memory
polymer causing a change in the shape memory polymer configuration;
and cooling the shape memory polymer to a temperature below the
transformation temperature to maintain the change in the
configuration of the shape memory and maintain at least contact
between the shape memory polymer and at least a portion of the
section of deposit material therein for retaining at least the
section of deposit material in the shape memory material.
18. The method of claim 17, additionally including heating the
shape memory polymer and then inserting at least the section of
deposit material therein.
19. The method of claim 17, wherein heating the shape memory
polymer is carried out, using heated fluid or laser light.
20. The method of claim 17, wherein applying a differential
pressure is carried out between a vacuum and hydrostatic fluid
pressure.
21. The method of claim 17, wherein cooling the shape memory
polymer is carried out using cool fluid.
22. The method of claim 17, additionally including attaching the
shape memory polymer to a guide wire.
23. The method of claim 17, wherein applying a differential
pressure is carried out using at least mechanical pressure, and
utilizing means for causing the change in shape of the shape memory
polymer.
24. The method of claim 17, wherein the change in shape of the
shape memory polymer is carried out by forming spaced seals about
the shape memory polymer, and directing pressurized fluid onto the
shape memory polymer intermediate the spaced seals.
Description
BACKGROUND OF THE INVENTION
[0002] The present invention relates to the microgrippers,
particularly to shape memory polymer gripper/release mechanisms,
and more particularly to a method and apparatus for loading shape
memory gripper mechanisms.
[0003] In recent years, substantial research and development has
been directed to microactuators, microgrippers, etc. particularly
for medical applications and capable of operating in 250-500 .mu.m
diameter applications, such as the blood vessels in the human body.
Recently a shape memory polymer (SMP) material has been developed
wherein above a certain temperature (Tc) the material becomes soft
and can be shaped by applying pressure, and cooling to a
temperature below Tc, and upon reheating the material to a
temperature above Tc the material returns to its original
shape.
[0004] By the use of the SMP material, microgrippers have been
developed for applications such as depositing material (i.e.,
embolic coils) in the blood vessels. Due to the capability of the
SMP materials, a small SMP tube attached to a guide wire or
catheter is heated, an embolic coil, for example, is inserted in
the tube, and pressure is applied to the SMP material causing it to
conform about the coil, whereafter the SMP material is cooled
thereby freezing the SMP material in the formed shape thereby
gripping the coil, and upon reheating the SMP material the material
returns to its original shape thereby releasing the coil. Such SMP
microgrippers are described and claimed in copending U.S.
application Ser. No. 08/807,412 filed Feb. 28, 1997, entitled,
"Microfabricated Therapeutic Actuators", and assigned to the same
assignee.
[0005] The present invention involved the loading of the SMP tubing
with deposit material for medical applications, such as an embolic
coil, medication, etc., and for non-medical applications requiring
the delivery and release of components in normally inaccessible
areas. The apparatus of the present invention operates via
differential pressure between vacuum and hydrostatic water pressure
whereby an application of uniform pressure on the exterior of the
SMP tubing, with a vacuum on the interior thereof causes heated SMP
tubing to change shape and grip a device located therein, after
which the SMP tubing is cooled and thereby freezes in its changed
shape. The heating and the cooling of the SMP tubing can be
accomplished by the water utilized to produce the pressure for
changing the shape of the SMP tubing. The heating of the SMP tubing
may also be accomplished using optical fibers and laser light.
Also, either heated water passing through a catheter to which the
SMP tubing is attached or laser light via optical fibers packed to
the SMP tubing may be utilized to reheat the tubing and release the
device therefrom.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to enabling loading
of shape memory polymer material with a deposit material.
[0007] A further object of the invention is to provide a method for
loading a shape memory polymer tubing with a device to be gripped
and released thereby.
[0008] A further object of the invention is to provide a loading
mechanism for shape memory polymer gripper/release mechanisms.
[0009] Another object of the invention is to enable loading of a
shape memory polymer gripper/release mechanism utilizing
differential pressure on the external and internal areas of the
shape memory polymer material.
[0010] Another object of the invention is to provide loading of a
shape memory polymer tube with a device to be gripped/released
thereby, utilizing differential pressure between vacuum and
hydrostatic water pressure.
[0011] Another object of the invention is to provide loading of a
shape memory polymer gripper/release tubing utilizing pressured
water which is heated and cooled on the external area of the tubing
while drawing a vacuum in the internal area thereof, and applying a
mechanism to areas of the heated external area of the tubing to
form depressions therein which are frozen in the tubing by cooling
of the external area.
[0012] Another object of the invention is to provide loading for a
shape memory polymer gripper/release tubing utilizing laser heating
of the tubing and differential pressure and cooling for forming
depressions in the tubing for gripping a device positioned
therein.
[0013] Other objects and advantages will become apparent from the
following description and accompanying drawing. The invention
involves the loading of a shape memory polymer SMP gripper/release
mechanism with a device to be gripped and released. The invention
is carried out by inserting in an SMP tubing a device to be
gripped/released, utilizing differential pressure between the
internal and external areas of a SMP tubing after and/or during the
heating of the tube whereby depressions are formed in the tubing,
and thereafter cooled the tubing causing a freezing of the thus
formed depressions in the tubing which causes gripping of the
device located in the tubing. Release of the device from the SMP
tubing is accomplished by reheating the tubing such that it returns
to its original shape. The method and apparatus of this invention
requires the use of an SMP tubing having a glass transformation
temperature (Tg) which when heated above Tg can be reshaped, and
subsequent cooling below Tg freezes to tubing in its reshaped
configuration. The heating and/or cooling can be provided by the
same water applied for pressurization, or the heating can be
provided by optical fibers packaged with the SMP tubing via which
laser light, for example, is directed onto the tubing. The heating
and cooling may be carried out during pressurization of the tubing
by controlling the temperature of the water used in the
differential pressure application to the tubing.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The drawings, which form a part of the disclosure,
illustrate the method and apparatus of the invention, and together
with the description, exemplify and teach the principles of the
invention.
[0015] FIG. 1 is a partial cross-sectional view of an embodiment of
a loaded shape memory polymer gripper/release mechanism which has
been loaded in accordance with the present invention.
[0016] FIGS. 2-5 illustrate the method for loading the
gripper/release mechanism of FIG. 1.
[0017] FIG. 6 illustrates schematically and in partial
cross-section an embodiment of the differential pressure apparatus
for loading a shape memory polymer tubing in accordance with the
invention.
[0018] FIG. 7 illustrates schematically and in partial
cross-section another embodiment of the loading apparatus, similar
to FIG. 6, but utilizing laser light via optical fibers for heating
the tubing, for both gripping and releasing a deposit material.
[0019] FIGS. 8-11 illustrate embodiments of loading mechanisms
utilizing mechanical pressure to load a shape memory polymer
tubing.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention is directed to loading shape memory
polymer gripper/release mechanisms with a deposit material. The
invention involves a method and loading apparatus to enable
gripping and release of a deposit material utilizing a shape memory
polymer (SMP) tubing and heating the tubing to be above the glass
transformation temperature (Tg) while reshaping the tubing via
differential pressure, and subsequently cooling the tube to below
the Tg to freeze the shape. Upon reheating the SMP tubing to a
temperature above the Tg it returns to its original shape. Thus, by
utilizing the SMP tubing as a gripper/release mechanism, it can be
utilized for gripping/releasing devices such as embolic coils,
medicine, etc. at a point of use as described and claimed in
above-referenced application Ser. No. 08/807,412. The loading of
the SMP gripper/release mechanism is carried in accordance with the
present invention by utilizing a differential pressure between the
interior and exterior of the heated SMP tubing. For example, the
differential pressure between vacuum on the interior of the tubing
and hystrostatic water pressure on the exterior of the tubing is
used to form indentations in the SMP tubing which function to grip
a device positioned in the tubing. Also, by applying vacuum to the
interior, mechanical pressure can be applied to the exterior. In
addition, the water utilized to produce the hydrostatic pressure on
the tubing can be heated to cause the tubing temperature to raise
above the Tg temperature, and the same water can be cooled to cool
the tubing to below the Tg temperature which results in a freezing
of the tubing in its reformed shape. Also, controls may be utilized
to enable simultaneous heating and pressurization of the water,
and/or simultaneous pressurization and cooling to enable a
continuous heating, pressurization, and cooling sequence. Also,
instead of utilizing water to heat the SMP tubing, laser light may
be directed into the interior of tubing via optical fibers. Either
laser light or warm water may be used to reheat the SMP tubing
above its Tg temperature to allow it to return to its original
shape and to release any device previously gripped therein. The
apparatus of the present invention enables the application of
uniform pressure to secure a grip on a deposit material via
differential pressure.
[0021] In addition to medical applications for depositing materials
in blood vessels in the human body, having a 250-500 .mu.m
diameter, the SMP gripper/release mechanism can be used for various
non-medical applications, such as assembly of read-write heads for
disk drives and other microassembly applications.
[0022] As pointed out above, the SMP gripping principle is based on
the unique property of the shape memory polymer. This polymer
possesses a glass transformation temperature (Tg) above which the
material enters a reversible glassy phase where it becomes soft and
flexible and easy to reshape. Once reshaped and cooled below Tg,
the new shape is frozen in place and the material becomes hardened
to over five (5) times the elastic modules of the glassy phase.
Upon reheating the material to a temperature above Tg it returns to
its original shape. By way of example, the Tg of the SMP material
is in the range of 25 to 75.degree. C., and the material may be
manufactured to produce a Tg anywhere in this range. In the SMP
tubing utilized to experimentally verify the present invention the
SMP tubing, manufactured by Mitsubishi, had a Tg of 55.degree.
C.
[0023] Prior to a detailed description of the method and apparatus
of the present invention, a broad description thereof is as
follows: First, the SMP tubing, which may be retained at the end of
catheter, guide wire, or optical fiber, as illustrated in the
drawings, will be heated above its transformation temperature Tg
by, for example, warm water, as shown in FIG. 6, or laser light via
an optical fiber, as shown in FIG. 7, and will become soft for
conforming to gripped configurations, such as shown in FIGS. 1, 6,
and 7. then the loading mechanism (see FIGS. 6 and 7) will provide
a force to conform the SMP tubing about a deposit material or
device, such as an end of an embolic coil. The loading apparatus is
operated by providing a pressure difference inside and outside of
the SMP tubing, for example, either by providing vacuum to the
inside or hydrostatic pressure to the outside, or both. As the
pressure is applied, the SMP tubing conforms into or partially into
grooves in the device positioned therein and provide a packaged
locking configuration. At this point, the warm water or laser light
heating is replaced with cold water or other cooling means to cool
the SMP tubing below the Tg to freeze it into the locking
configuration. In the loading apparatus illustrated in FIGS. 6 and
7, a plurality of movable members containing O-rings are utilized
to provide a sealed compartment for water to produce
heating/cooling for conforming of the SMP tubing as described in
detail hereinafter. These movable members may be located on
opposite sides of the tubing, or spaced around tubing so that
pressure thereon, such as hydrostatic water pressure moves the
members into contact with the tubing and the water pressure passing
through openings in the members form indentations in the tubing to
secure the deposit material or device therein. In addition to the
use of water to heat, pressurize and cool the SMP tube, the water
can be used to heat and cool the tubing and mechanical pressure can
be used to move the members against the outer surface of the SMP
tube, with or without a vacuum within the tubing. Also, a
combination of laser light heating and water cooling can be
utilized with either hydrostatic water or mechanical pressure being
applied to conform the tubing about a device therein. FIGS. 8-10
illustrate mechanical arrangements for conforming the SMP tubing
about a device to be retained therein.
[0024] Referring now the FIGS. 1-5, wherein FIG. 1 illustrates an
embodiment of a shape memory polymer (SMP) gripper/release
mechanism, made by the method schematically illustrated in FIGS.
2-5. The method for producing the embodiment of FIG. 1, as
illustrated in FIGS. 2-5 is exemplified as follows:
[0025] 1. Heat is applied to an SMP tubing 10, having a glass
transformation temperature of 35-65.degree. C., as indicated by
legend and arrows 11 in FIG. 2 to a temperature above Tg. The heat
may be produced by a fluid such as hot water, gas, oil, etc.,
having a temperature of 45 to 65.degree. C., applied to the
external surface 12 of tubing 10, or by laser light transmitted to
the interior surface 13 of tubing 10 via optical fibers adapted to
be positioned in an opening 14 of a tube 15, secured in one end 16
of tubing 10. The optical fibers may replace the tube 15. By way of
example, the tubing 10 may have an internal diameter of 200 .mu.m
to 1000 .mu.m and an external diameter of 250 .mu.m to 1050 .mu.m.
The tube 15 may be replaced with a solid guide wire.
[0026] 2. An end section 17 of a deposit material 18, such as an
embolic coil, is inserted through an end 19 of tubing 10 into the
interior of the tubing 10, as shown in FIG. 3, with end section 17
provided with one groove or a plurality of spaced grooves 20. If
desired the end section 17 can be inserted prior to heating the
tubing. The external diameter of end section 17 being slightly
smaller than the internal diameter of tubing 10 so as to provide
easy insert of the end section 17 into tubing 10. By way of
example, the grooves 20 may have a width of 25 .mu.m to 200 .mu.m
and diameter of 150 .mu.m to about 500 .mu.m, and spaced about a
distance of 50 .mu.m to 150 .mu.m, with end section 17 having an
external diameter of 180 .mu.m to about 500 .mu.m.
[0027] 3. Pressure is applied to the external surface of heated
tubing 10 as indicated by legend and arrows 21 in FIG. 4, while a
vacuum is drawn on the internal surface 13 of tubing 10 as
indicated by legend and arrows 22. The pressure 21 may be produced
by hydrostatic water, gas, or oil pressure or mechanical pressure.
The vacuum 22, produced by a pump, not shown, may be at a Torr of
10.sup.-4 to 1. If produced by hystrostatic pressure, the water
used to heat the tubing 10 may be pressurized to a pressure of 800
to 3000 Torr. As seen in FIG. 4, the pressure on heated tubing 10
causes sections of the tubing adjacent grooves 20 of end section 17
to conform or indent as indicated at 23. While not shown in FIG. 4,
heat 11 may be applied to tubing 10 simultaneously with pressure 21
to maintain the tubing 10 soft and pliable. Also, pressure 21 may
be applied without vacuum 22 but such decreases the differential
between the external and internal surfaces of tubing 10 and thus
the external pressure would need to be increased to produce the
same results. The indentations 23 provide a locking between tubing
10 and end section 17.
[0028] 4. The tubing 10 is cooled as indicated by legend and arrows
24, as shown in FIG. 5, to a temperature below Tg, whereby the
indentations 23 are frozen, and the indentations 23 of tubing 10
remain in their locked position within grooves 20 of end section
17. The cooling 24 may be carried out using cold water or other
cooling means (gas, oil, etc.), and can be carried simultaneously
with pressure 21 remaining applied. If cooling 24 is carried out by
water, a water temperature of 5 to 25.degree. C. may be used, and
the cooling water may be the same as used for heating tubing 10
and/or for producing the hystrostatic pressure 21. Upon cooling of
the tubing 10, an SMP gripper/release mechanism 25, as illustrated
in FIG. 1, is produced, wherein end section 17 of the deposit
material 18 is gripped by tubing 10 which is attached to tubing 15,
which may, for example, be attached to a catheter or guide wire for
insertion into a blood vessel of a human body, or a guide wire may
be utilized in place of tubing 15 to insert the gripper release
mechanism 25 and a deposit material 18 into a non-medical
inaccessible area.
[0029] Upon the SMP gripper/release mechanism and loaded deposit
material be positioned by the guide wire at a point of use, the SMP
tubing 10 is heated to a temperature above the Tg of tubing 10,
which allows the tubing 10 to revert to its original configuration
thereby removing the indentations 23 in tubing 10 allowing the end
section 17 of deposit material 18 to be released up removing the
tubing 10 from the area of use of the deposit material 18.
Reheating of the tubing 10 to above it temperature Tg can be
carried out, for example, by injecting hot water through the
opening 14 of tubing 15 into the interior of tubing 10, or by
directing laser light via optical fibers in opening 14 of tubing 15
into the interior of tubing 10. Also, a solid guide wire with
optical fibers wrapped therearound may be utilized in place of
tubing 15.
[0030] FIG. 6 illustrates schematically an embodiment of a loading
mechanism utilizing differential pressure involving hydrostatic
pressure and vacuum on the exterior and interior of the SMP tubing.
Components corresponding to components of the FIG. 1 embodiment
will be given corresponding reference numerals. As shown, an end
section 17 of a deposit material 18 is positioned in an SMP tubing
10 secured at one end to a guide wire or optical fiber 15', the end
section 17 including a plurality of spaced grooves 20. In this
embodiment arrows 11/21/24 are utilized to indicate heating of,
pressure on, and cooling of the SMP tubing 10, as in the
operational sequence described above with respect to FIGS. 2 and 5,
using water to apply the pressure (21) and warm water for heating
(11), or cold water for cooling (24). A pressure differential
loading mechanism generally indicated at 30 comprises a plurality
of members positioned about the SMP tubing 10, two members 31 and
32 being illustrated in this embodiment, with members 31, 32 being
provided with openings 33 to allow passage of
heating/pressure/cooling water as indicated by arrows 11/21/24.
Each of members 31-32 is provided with at least one groove 34 in
which flexible members or O-rings 35 and 36 are retained around SMP
tubing 10. As differential pressure indicated by arrows 21' is
applied against the members 31-32 and a vacuum 22 is drawn on the
interior of tubing 10, the flexible members or O-rings 35 and 36
are pressed against the external surface of heated SMP tubing 10
producing indentations 23' in the tubing, and forming a seal around
the tubing 10 which defines a compartment or area 37 between
O-rings 35-36 and between tubing 10 and members 31-32. As
pressurized fluid (water) flows through opening 33, indentations 38
are formed in tubing 10 which provide locking between the SMP
tubing 10 and the end section 17 of the deposit material 18. As
described above, the pressure 21' on members 31-32 can be
maintained during cooling. Note that the sealing indentations 23'
in FIG. 6 have been illustrated as not extending into the grooves
20 of end section 17 while indentations 38 extend into grooves 20.
The location of the indentations 23' and 38 with respect to the
grooves 20 of end section 17 is dependent on the location of end
section 17 within SMP tubing 10 and the location of the flexible
members or O-rings 35-36.
[0031] Various modification of the loading apparatus 30 may be
utilized. For example, the members 31 and 32 may be provided with a
plurality of openings therein to provide for passage of
heating/cooling water. Also, there may be a plurality of loading
members located in spaced relation around the SMP tubing so that
the sealing indentations 23' extends around the tubing. The spacing
of the loading members must be such as to allow movement thereof by
hydrostatic pressure, for example, or by mechanical pressure if
desired, to produce the desired sealing indentations in the SMP
tubing. In addition, if desired, additional flexible members or
O-rings, such as shown at 35 and 36 located in additional grooves
in members 31-32 may be utilized to form additional compartments or
areas therebetween. Also, instead of flexible members or O-rings,
balls secured in the grooves of the members 31-32 may be utilized
to mechanically provide tubing indentations as shown in FIG. 8.
Also, forming protruding sections on the members 31-32 in place of
the grooves and flexible members or O-rings may be utilized to
produce the desired indentations in the heated SMP tubing.
[0032] FIG. 7 illustrates a loading mechanism similar to that of
FIG. 6 except that heating of the SMP tubing is carried out by
directing laser light into the interior of the tubing via optical
fibers. In FIG. 7, the end section of the deposit material is shown
only partially inserted into the SMP tubing to enable dearer
illustration of the laser beam heating the SMP tubing. Components
similar to the components of FIG. 6 are given corresponding
reference numerals. As shown, an optical fiber 40 positioned in
opening 14 of tubing 15 is secured to one end of SMP tubing 10. A
plurality of optical fibers 40 may be utilized. Laser light
indicated at 41 is passed through optical fiber 40 into the
interior 42 of SMP tubing 10 for heating the tubing to a
temperature above the Tg, as described above. In this embodiment,
as in FIG. 6, the end section 17 of the deposit material may be
inserted into the SMP tubing after or prior to heating of the
tubing. However, where laser light is utilized to heat the tubing
it is more efficient to only partially insert the end section prior
to heating, as shown in FIG. 7, whereby the laser light will bounce
off the end of the end section 17 rather than passing out the end
of the SMP tubing, thereby providing more efficient heating. By way
of example the laser light 41 may be at a wavelength of 400 nm to
1000 nm. As pointed out above, a solid guide wire with optical
fiber wrapped around or along the external surface thereof may be
utilized in place of tubing 15 with optical fiber 40 therein.
[0033] After heating of the SMP tubing 10 by laser light as shown
in FIG. 7, and the end section 17 of the deposit material is
inserted into the SMP tubing, as in FIG. 6, the operation of the
loading mechanism 30 as described above with respect to FIG. 6 is
carried out to produce and freeze the indentations 38 in SMP tubing
10, not shown in FIG. 7.
[0034] While not shown, the hydrostatic water pressure 21, as well
as the heating water and/or cooling water, may utilize the same
water which flow is controlled and passes through a heating means,
a pressurizing pump, and a cooling means, or means for a
heating/pressurization operation and/or a pressurization/cooling
operation. Such controlled systems can be readily utilized using
computer control known in the art. Such
heating/pressurization/cooling operations can be carried out in a
controlled sequence to enable efficient manufacturing of shape
memory polymer gripper/release mechanisms in various sizes and for
various applications.
[0035] FIG. 8 illustrates a loading apparatus generally similar to
FIG. 6 except that the indentations in the SMP tubing are formed
mechanically instead of hydrostatically. Similar components to
those of FIG. 6 are given corresponding reference numerals. The
only structural difference from the FIG. 6 embodiment is the
replacement of the flexible members or O-rings with a plurality of
ball, only four (4) such balls being shown in FIG. 8 at 50-53. As
in the FIG. 6 embodiment, warm or cold water indicated by arrows
11/24 is utilized to heat and/or cool the SMP tubing, but
mechanical pressure indicated by arrows 21' in FIG. 8 is used to
form indentations 23', the only indentations formed in SMP tubing
10. The depth of the indentations 23' is dependent on the relative
location of balls 50-53 with respect to grooves 20 in end section
17 of deposit material 18. As shown in FIG. 8, the indentations 23'
are sufficient to retain the end section 17 within SMP tubing 10,
even though such do not fully extend into grooves 20 of end section
17 as does indentations 38 in the FIG. 6 embodiment. The mechanical
pressure 21' on members 31 and 32 may be provided by conventional
press technology, for example. While only four (4) balls 50-53 are
shown, grooves 34 in members 31 and 32 may contain any desired
number of balls, each forming an indentation 23' in the SMP tubing
10 when pressure 21' is applied.
[0036] FIG. 9 illustrates a loading apparatus utilizing a
mechanical clamp arrangement. In this embodiment of an apparatus
generally indicated at 30', a coil or deposit material 18 is
positioned in a SMP tubing 10, as in FIG. 6, and a pair of
mechanical clamps 60 and 61 having liners or members 62 and 63,
constructed of a polymer or high CTE material, which are forced
against the heated SMP tubing 10 when the damps 60 and 61 are
forced toward each other causing indentations in the heated SMP
tubing 10, the pressure on the clamps 60 and 61 being maintained
until the SMP tubing 10 has cooled below the Tg temperature
thereof, whereby the indentations are frozen in the SMP tubing
until it is reheated above its Tg, and the pressure on the clamps
60-61 withdrawn. Movements of the clamps 60-61 being shown by
double arrow 64. The liners members 62 and 63 may be of a variety
of configurations including spaced sections, protruding sections,
etc., and located to form indentations at any desired location on
the deposit material or coil 18 so as to retain same within the
cooled SMP tubing 10.
[0037] FIG. 10 schematically illustrates a loading mechanism using
mechanical damping with alignment pins. In this arrangement an SMP
tubing 70 is secured at one end to a guide wire, optical fiber or
catheter 71, with an end 72 of a deposit material 73 being inserted
into an opposite end of SMP tubing 70, by a retain means 74. The
loading mechanism comprises a pair of annular matching spaced
members, only a portion of each pair shown at 75 and 76 and having
openings 77 and 78, respectively, within which the SMP tube 70 and
the end 72 of deposit material 73 are inserted, with opening 78
being of a smaller diameter than opening 77. Members 75 and 76
additionally include openings 79-80 and 81-82 through which
alignment pins 83 and 84 are inserted to align members 75 and 76,
which are spaced from each other to define compartments or areas 85
and 86. Member 76 is provided with a tapered surface 87 adjacent
opening 78.
[0038] In operation of the FIG. 10 mechanism, pressure is applied
to the pairs of members which cause member 75 and tapered surface
87 of member 76 to contact the SMP tubing 70 forming a seal
therebetween whereafter fluid pressure indicated by arrows 88 is
directed through compartments of areas 85 and 86 causing an end 89
of the SMP tubing 70 to conform to the shape of the end 72 of
deposit material 73, and upon cooling the SMP tubing 70 as
described above, the end 72 of deposit material 73 is retained
within the end 89 of SMP tubing 70. However, pressure applied by
the tapered surface 87 may be utilized as a clamping surface to
cause the end of 89 of tubing 70 in conforming to the shape of the
end 72 of deposit material 73.
[0039] FIG. 11 illustrates an inverted version of the loading
mechanism of FIG. 10, the difference being that the end 72' of
deposit material 73 is inserted into the end 89 of SMP tubing 70,
thus eliminating the retainer mechanism 74 of FIG. 10, whereafter
the SMP tubing 70 and the deposit material 73 are inserted through
opening 77 of member 75 and into opening 78 in member 76 as
indicated by arrow 90 until the end 89 of SMP tubing contacts
tapered surface 87 of member 76, whereafter pressure fluid is
directed into areas 85 and 86 causing the end 89 of SMP tubing 70
to fully conform to the external surface of end 72 of deposit
material 73, as described above. In the FIG. 11 embodiment the
initial I.D. of SMP tubing 70 is slightly greater than the O.D. of
the end 72 of the deposit material 73 so that the deposit material
is initially retained in the end of the SMP tubing 70 by the close
fit.
[0040] It has thus been shown, that the present invention provides
a method and apparatus for loading shape memory polymer (SMP)
gripper/release mechanism. The invention utilizes differential
pressure, such as between vacuum and hydrostatic water pressure, to
produce indentations in SMP tubing for retaining deposit material
therein. The invention utilizes heated water or laser light to heat
the SMP tubing, and water to cool the tubing after the indentations
are formed to freeze same in a locking position about the deposit
material. The same water may be utilized for heating,
pressurization, and cooling of the SMP tubing. The invention
enables the efficient and inexpensive manufacture of SMP
gripper/release mechanisms for various applications, particularly
those requiring operation in areas of 250-500 .mu.m diameters.
[0041] While particular embodiments of the invention have been
illustrated and/or described and particular operational sequences
have been described, along with exemplary parameters, materials,
etc., such are not intended to be limiting. Modifications and
changes may become apparent to those skilled in the art, and it is
intended that the invention be limited only by the scope of the
appended claims.
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