Title: Conductive inks for metalization in integrated polymer microsystems
Abstract: A system of metalization in an integrated polymer microsystem. A flexible polymer substrate is provided and conductive ink is applied to the substrate. In one embodiment the flexible polymer substrate is silicone. In another embodiment the flexible polymer substrate comprises poly(dimethylsiloxane).
Patent Number: 7,005,179 Issued on 02/28/2006 to Davidson, et al.
| Inventors:
|
Davidson; James Courtney (Livermore, CA);
Krulevitch; Peter A. (Pleasanton, CA);
Maghribi; Mariam N. (Livermore, CA);
Benett; William J. (Livermore, CA);
Hamilton; Julie K. (Tracy, CA);
Tovar; Armando R. (San Antonio, TX)
|
| Assignee:
|
The Regents of the University of California (Oakland, CA)
|
| Appl. No.:
|
371912 |
| Filed:
|
February 20, 2003 |
| Current U.S. Class: |
428/209; 174/254; 174/255; 174/258; 428/901 |
| Current Intern'l Class: |
B32B 3/00 (20060101) |
| Field of Search: |
428/209,901
174/253,254-255,268,258
|
References Cited [Referenced By]
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| 4759965 | Jul., 1988 | Kato et al.
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| 5047283 | Sep., 1991 | Leatherman et al.
| |
| 5087494 | Feb., 1992 | Calhoun et al.
| |
| 5219655 | Jun., 1993 | Calhoun et al.
| |
| 5346850 | Sep., 1994 | Kaschmitter et al.
| |
| 5369881 | Dec., 1994 | Inaba et al.
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| 5395481 | Mar., 1995 | McCarthy.
| |
| 5414276 | May., 1995 | McCarthy.
| |
| 5468918 | Nov., 1995 | Kanno et al.
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| 5473118 | Dec., 1995 | Fukutake et al.
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| 5512131 | Apr., 1996 | Kumar et al.
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| 5817550 | Oct., 1998 | Carey et al.
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| 6207259 | Mar., 2001 | Iino et al.
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| 6324429 | Nov., 2001 | Shire et al.
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| 6413790 | Jul., 2002 | Duthaler et al.
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| 6426143 | Jul., 2002 | Voss et al.
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| 6596569 | Jul., 2003 | Bao et al.
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| 6841228 | Jan., 2005 | Edwards et al.
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| 2002/0050220 | May., 2002 | Schueller et al.
| |
| 2002/0079219 | Jun., 2002 | Zhao et al.
| |
| Foreign Patent Documents |
| 0 340 376 | Nov., 1989 | EP.
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| 0 935 288 | Nov., 1999 | EP.
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| 2033667 | May., 1980 | GB.
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| WO 99/1660/1 | Apr., 1999 | WO.
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| WO 01/4151/7 | Jun., 2001 | WO.
| |
| WO 01/8978/7 | Nov., 2001 | WO.
| |
Other References
Knobloch, A., et al., "Printed Polymer Transistors," First International IEEE
Conference on Polymers and Adhesives in Microelectronics and Photonics, Incorporating
Poly, Pep & Adhesives in Electronics Proceedings, Potsdam, Germany, Oct. 21-24,
2001, pp. 84-90.
|
Primary Examiner: Lam; Cathy F.
Attorney, Agent or Firm: Scott; Eddie E., Thompson; Alan H.
Goverment Interests
The United States Government has rights in this invention pursuant to Contract
No. W-7405-ENG-48 between the United States Department of Energy and the University
of California for the operation of Lawrence Livermore National Laboratory.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Application No. 60/398,702
filed Jul. 26, 2002 and titled "Conductive Inks for Multilevel Metalization in
Stretchable Integrated Polymer Microsystems." U.S. Provisional Application No.
60/398,702 filed Jul. 26, 2002 and titled "Conductive Inks for Multilevel Metalization
in Stretchable Integrated Polymer Microsystems" is incorporated herein by this reference.
Claims
What is claimed is:
1. An electronic apparatus comprising:
a flexible polymer substrate, said flexible polymer substrate consisting of silicone; and
circuit lines operatively connected to said flexible polymer substrate, said
circuit lines consisting of
three-dimensional microfluidic channels in said flexible polymer substrate and
conductive ink filling said three-dimensional microfluidic channels,
wherein said circuit lines are produced by the method comprising the step of
producing three-dimensional microfluidic channels in said flexible polymer substrate
and the step of applying conductive ink to fill said three-dimensional microfluidic
channels in said substrate to produce the electronic apparatus with said circuit
lines in said flexible polymer substrate comprised of said conductive ink filling
said three-dimensional microfluidic channels.
2. The electronic apparatus of claim 1 wherein said conductive ink filling said
three-dimensional microfluidic channels is electrically conductive screen printable ink.
3. The electronic apparatus of claim 1 wherein said flexible polymer substrate
consisting of silicone comprises poly(dimethylsiloxane).
4. The electronic apparatus of claim 1 including the step of curing said conductive
ink to produce said circuit lines.
5. The electronic apparatus of claim 1 wherein said step of filling said three-dimensional
microfluidic channels with said conductive ink comprises injecting said conductive
ink into said three-dimensional microfluidic channels.
6. The electronic apparatus of claim 1 wherein said step of filling said three-dimensional
microfluidic channels with said conductive ink comprises injecting said conductive
ink into said three-dimensional microfluidic channels using a syringe.
7. The electronic apparatus of claim 1 wherein said step of filling said three-dimensional
microfluidic channels with said conductive ink comprises using a vacuum to draw
said conductive ink through said three-dimensional microfluidic channels.
Description
BACKGROUND
1. Field of Endeavor
The present invention relates to electronics and more particularly to metalization
in integrated polymer microsystems.
2. State of Technology
U.S. Pat. No. 5,817,550 for a method for formation of thin film transistors
on plastic substrates to Paul G. Carey, Patrick M. Smith, Thomas W. Sigmon, and
Randy C. Aceves, issued Oct. 6, 1998, assigned to Regents of the University of
California, provides the following background information, "Recently a process
was developed for crystallizing and doping amorphous silicon on a low cost, so-called
low-temperature plastic substrate using a short pulsed high energy source in a
selected environment, without heat propagation and build-up in the substrate so
as to enable use of plastic substrates incapable of withstanding sustained processing
temperatures higher than about 180° C. Such a process is described and claimed
in U.S. Pat. No. 5,346,850 issued Sep. 13, 1994 to J. L. Kaschmitter et al., assigned
to the Assignee of the instant application. Also, recent efforts to utilize less
expensive and lower temperature substrates have been carried out wherein the devices
were formed using conventional temperatures on a sacrificial substrate and then
transferred to another substrate, with the sacrificial substrate thereafter removed.
Such approaches are described and claimed in U.S. Pat. No. 5,395,481 issued Mar.
7, 1995, U.S. Pat. No. 5,399,231 issued Mar. 21, 1995, and U.S. Pat. No. 5,414,276
issued May 9, 1995, each issued to A. McCarthy and assigned to the assignee of
the instant application."
U.S. Pat. No. 6,324,429 for a chronically implantable retinal prosthesis by
Doug Shire, Joseph Rizzo, and John Wyatt, of the Massachusetts Eye and Ear Infirmary
Massachusetts Institute of Technology issued Nov. 27, 2001 provides the following
information, "In the human eye, the ganglion cell layer of the retina becomes a
monolayer at a distance of 2.5-2.75 mm from the foveola center. Since the cells
are no longer stacked in this outer region, this is the preferred location for
stimulation with an epiretinal electrode array. The feasibility of a visual prosthesis
operating on such a principle has been demonstrated by Humayun, et al. in an experiment
in which the retinas of patients with retinitis pigmentosa, age-related macular
degeneration, or similar degenerative diseases of the eye were stimulated using
bundles of insulated platinum wire."
SUMMARY
Features and advantages of the present invention will become apparent from
the following description. Applicants are providing this description, which includes
drawings and examples of specific embodiments, to give a broad representation of
the invention. Various changes and modifications within the spirit and scope of
the invention will become apparent to those skilled in the art from this description
and by practice of the invention. The scope of the invention is not intended to
be limited to the particular forms disclosed and the invention covers all modifications,
equivalents, and alternatives falling within the spirit and scope of the invention
as defined by the claims.
The present invention provides a system of metalization in an integrated flexible
polymer microsystem. A flexible polymer substrate is provided and conductive ink
is applied to the substrate. In one embodiment the flexible polymer substrate is
silicone. In another embodiment the flexible polymer substrate comprises poly(dimethylsiloxane).
In one embodiment an electronic apparatus is produced comprising a flexible polymer
substrate and circuit lines operatively connected to the flexible polymer substrate
wherein the circuit lines are produced by the method comprising the step of applying
conductive ink to the substrate.
The invention is susceptible to modifications and alternative forms. Specific
embodiments are shown by way of example. It is to be understood that the invention
is not limited to the particular forms disclosed. The invention covers all modifications,
equivalents, and alternatives falling within the spirit and scope of the invention
as defined by the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated into and constitute a part
of the specification, illustrate specific embodiments of the invention and, together
with the general description of the invention given above, and the detailed description
of the specific embodiments, serve to explain the principles of the invention.
FIG. 1 illustrates an embodiment of a system incorporating the present invention.
FIG. 2 illustrates another embodiment of a system incorporating the present invention.
FIG. 3 illustrates another embodiment of a system incorporating the present invention.
FIGS. 4A and 4B illustrate an embodiment of an alignment apparatus used in
screen printing multiple layers of metalization.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, to the following detailed description, and
to incorporated materials; detailed information about the invention is provided
including the description of specific embodiments. The detailed description serves
to explain the principles of the invention. The invention is susceptible to modifications
and alternative forms. The invention is not limited to the particular forms disclosed.
The invention covers all modifications, equivalents, and alternatives falling within
the spirit and scope of the invention as defined by the claims.
Referring now to in FIG. 1, an embodiment of a system constructed in accordance
with the present invention is illustrated. The system is generally designated by
the reference numeral
100. As shown in FIG. 1, an electronic unit
104,
a processor chip
105, a battery
106, and an antenna
107 are
connected by a circuit integrated onto a PDMS substrate
101. The circuit
interconnect is comprised of circuit lines
102,
103, and
108.
The substrate
101 comprises a poly(dimethylsiloxane) (PDMS) substrate
that serves as a platform for integrating and packaging the individual components.
The electronic unit
104 can be a wide variety of electronic devices. Examples
of some of the electronic devices that are utilized in different embodiments of
the invention include the following: electrode array, implantable medical device,
radio, recorder, recorder and player, video camera, video player, video recorder,
video recorder and player, cell phone, computer, calculator, phone tap, gadget
that detects phone taps, audio surveillance device, medical device, biosensor,
radiation monitor, power source, battery, solar cell, wireless electronics for
communication, capacitor, resistor, inductor, transformer, light-emitting diode,
optical detector, optical encoder, integrated circuit, microprocessor, digital
to analog converter, display, camera, cell phone, and other electronic devices.
Devices are attached to an activated flexible polymer substrate. In the case of
PDMS substrates both the substrate and the device passivating oxide are cleaned
in ethanol prior to an oxygen plasma. Devices are then permanently bonded to the
substrate upon contact.
In order for the PDMS substrate
101 to be an ideal, low cost, integration
and packaging platform, demonstration of metalization to create the circuit lines
102,
103, and
108 is important. The metalization comprises
metal interconnect using conductive inks to create the circuit lines
102,
103, and
108. The electronic unit
104 and processor chip
105
are connected by the conductive lines
102. The processor chip
105
and battery
106 are connected by the conductive lines
103. The processor
chip
105 and antenna
107 are connected by the conductive line
108.
The battery
105 provides power to the processor chip
105 and the
electronic unit
104. The antenna
107 allows information that has
been obtained by the system
100 to be transmitted to a remote receiver.
The drawings and written description illustrate a number of specific embodiments
of the invention. These embodiments and other embodiments give a broad illustration
of the invention. Various changes and modifications within the spirit and scope
of the invention will become apparent to those skilled in the art. Applicants will
describe four (4) embodiments of creating the circuit lines
102,
103,
and
108. The first method utilizes "3D Microfluidic Networks."
In one embodiment, applicants produce three-dimensional microfluidic channels
in the PDMS substrate
101. Applicants then fill the microfluidic networks
with liquid conductive ink. Applicants then cure the ink to produce embedded conducting
networks within the PDMS substrate
101. A syringe is used to inject the
ink into the channels to allow for an even distribution throughout the structure.
Alternatively, a vacuum can be used to draw the ink through the microfluidic network.
After the ink is dispersed throughout the channels it is then cured producing conductive
micron-scale wires.
In a preliminary experiment, a set of four channels with different diameters
was
created in a 49 mm long block of PDMS with the conductive ink (Conductive Compounds,
AG-500, silver filled electrically conductive screen printable ink/coating) injected
into each channel. Channel sizes ranged from 100 microns to 378 microns in diameter.
After curing, all four lines were found to be electrically continuous.
The Microfluidic Networks can be produce as described in International Patent
No. WO0189787 published Nov. 29, 2001 and May 30, 2002, titled "MICROFLUIDIC SYSTEMS
INCLUDING THREE-DIMENSIONALLY ARRAYED CHANNEL NETWORKS," to the President and Fellows
of Harvard College invented by Anderson et al. This patent describes methods for
fabricating improved microfluidic systems, which contain one or more levels of
microfluidic channels. The microfluidic channels can include three-dimensionally
arrayed networks of fluid flow paths therein including channels that cross over
or under other channels of the network without physical intersection at the points
of cross over. The microfluidic networks of the can be fabricated via replica molding
processes. International Patent No. WO0189787 and the information and disclosure
provided thereby is incorporated herein by reference.
In another embodiment, applicants produce three-dimensional microfluidic channels
in the PDMS substrate
101 using a stamp to place the ink in a desired pattern
on layers of PDMS. An description of a deformable stamp for patterning a surface
is shown in U.S. Patent Application No. 2002/0050220 for a deformable stamp for
patterning three-dimensional surfaces by Olivier Schueller, Enoch Kim, and George
Whitesides published May 5, 2002. U.S. Patent Application No. 2002/0050220 is incorporated
herein by reference.
The stamp can be placed in contact with an entire 3-dimensional object, such
as a rod, in a single step. The stamp can also be used to pattern the inside of
a tube or rolled over a surface to form a continuous pattern. The stamp may also
be used for fluidic patterning by flowing material through channels defined by
raised and recessed portions in the surface of the stamp as it contacts the substrate.
The stamp may be used to deposit self-assembled monolayers, biological materials,
metals, polymers, ceramics, or a variety of other materials. The patterned substrates
may be used in a variety of engineering and medical applications. This approach
can be used to pattern the conductive inks to produce multi level metalization
as follows:
1. An etched substrate of silicon, glass, or comparable type is used to
mold the PDMS to a desired pattern. Photoresist or other material can also be patterned
onto the silicon or glass substrate to create the mold.
2. The PDMS is applied on the mold, allowed to cure and then peeled away
from the substrate forming a stamp.
3. The conductive ink is then spin coated onto a second application wafer
to achieve a thin coating.
4. The PDMS stamp is then applied to this wafer allowing for the ink to
transfer from the application wafer to the stamp.
5. The PDMS stamp with the ink applied to it is aligned with the PDMS-coated
substrate wafer and placed in contact, then removed, transferring the ink.
6. The ink is then allowed to cure at the appropriate temperature for proper adhesion.
7. Once the ink is cured a layer of photoresist is applied and patterned
to produce posts that will form the interconnects between metal layers. This is
done using photolithography techniques.
8. A second layer of PDMS is applied to the substrate wafer to passivate
the first layer of metal without exceeding the height of the photoresist posts.
9. After curing the PDMS, the photoresist posts are removed in acetone,
leaving vias down to the underlying metal layer.
10. The holes are filled either by filling with conductive ink or by electroplating.
11. For multi-layer metalization steps 3-11 are repeated until the desired
number of levels are achieved.
Another embodiment of a system for creating the circuit lines
102,
103, and
108 is photolithography. Photoresist is spun onto the substrate
wafer and patterned, exposing the underlying PDMS layer in regions where the conductive
ink is to be applied. The conductive ink is then spread onto the substrate, either
by spin-coating or spraying. After curing, the photoresist is removed in acetone,
lifting off the undesired conductive ink. This process can be replicated until
the desired levels are completed.
Another embodiment of a system for creating the circuit lines
102,
103, and
108 is screen printing. To avoid the use of photoresist
and the possibility of losing excessive amounts of ink in the photolithography
process, the ink can simply be screen printed on using traditional techniques.
A permeable screen mesh of either monofilament polyester or stainless steel is
stretched across a frame. The frame with a stencil with the desired pattern is
placed on top of the wafer with cured PDMS. Using a squeegee the conductive ink
is pushed through the stencil and onto the substrate wafer. Another screen mesh
with stencil is used to apply the appropriate interconnections for each layer of
metalization. After which a second layer of PDMS is applied to the substrate wafer
to passivate the first layer of metal without exceeding the height of the metal
interconnections. This process is repeated until the desired number of levels is achieved.
Referring now to FIG. 2, another embodiment of a system constructed in
accordance with the present invention is illustrated. The system provides an electronic
apparatus. The system is generally designated by the reference numeral
200.
In the system
200 the electronic apparatus is produced by the steps (
201)
providing a flexible polymer substrate and (
202) applying conductive ink
to the flexible polymer substrate. Circuit lines are produced by applying the conductive
ink to the flexible polymer substrate. In one embodiment the flexible polymer substrate
is silicone. In another embodiment the flexible polymer substrate comprises poly(dimethylsiloxane).
The electronic apparatus can be a wide variety of electronic devices. Some examples
of electronic apparatus that can be produced include, but are not limited to, the
following: electrode array, implantable medical device, radio, recorder, recorder
and player, video camera, video player, video recorder, video recorder and player,
cell phone, computer, calculator, phone tap, gadget that detects phone taps, audio
surveillance device, medical device, biosensor, radiation monitor, power source,
battery, solar cell, wireless electronics for communication, capacitor, resistor,
inductor, transformer, integrated circuit, microprocessor, digital to analog converter,
display, camera, cell phone, and other electronic devices. Devices are attached
to an activated flexible polymer substrate. In the case of PDMS substrates both
the substrate and the device passivating oxide are cleaned in ethanol prior to
an oxygen plasma. Devices are then permanently bonded to the substrate upon contact.
FIG. 2 shows six different embodiments of steps for applying the conductive
ink to the flexible polymer substrate to create the circuit lines. The six different
steps of applying the conductive ink to the flexible polymer substrate are: step
203 spraying, step
204 spin-coating, step
205 screen printing,
step
206 creating three-dimensional microfluidic channels,
207 photolithography,
and
208 stamping.
In step
203 spraying, photoresist is spun onto the flexible polymer substrate
and patterned. This exposes the underlying flexible polymer substrate layer in
regions where the conductive ink is to be applied. The conductive ink is then spread
onto the flexible polymer substrate by spraying. After curing, the photoresist
is removed in acetone, lifting off the undesired conductive ink. This process can
be replicated until the desired levels are completed.
In step
204 spin-coating, photoresist is spun onto the flexible polymer
substrate and patterned, exposing the underlying flexible polymer substrate layer
in regions where the conductive ink is to be applied. The conductive ink is then
spread onto the flexible polymer substrate by spin-coating. After curing, the photoresist
is removed in acetone, lifting off the undesired conductive ink. This process can
be replicated until the desired levels are completed.
In step
205 screen printing, the conductive ink is screen printed using
traditional techniques. A permeable screen mesh of either monofilament polyester,
polyamide or stainless steel is stretched across a frame. The frame with a stencil
with the desired pattern is placed on top of the flexible polymer substrate. Using
a squeegee the conductive ink is pushed through the stencil and onto the subsequent
flexible polymer substrate. Another screen mesh with stencil is used to apply the
appropriate interconnections for each layer of metalization. After which a second
layer of flexible polymer substrate is applied to the flexible polymer substrate
to passivate the first layer of ink/metal without exceeding the height of the metal
interconnections. This process is repeated until the desired number of levels is
achieved. Stencil types can be direct or indirect mechanical or photomechanical.
In step
205b screen printed interconnect transfers, the conductive
ink is screen printed as in step
205 onto a carrier backing material such
as mylar or Kapton. The ink is cured before it is transferred in a decal fashion
onto the flexible polymer substrate. Multilple conductive ink transfer decals with
fiducial alignment marks are used to complete multiple interconnect routing levels.
In step
206 creating three-dimensional microfluidic channels, three-dimensional
microfluidic channels are created in the flexible polymer substrate. The microfluidic
networks are filled with liquid conductive ink. The ink is cured to produce embedded
conducting networks within the flexible polymer substrate. A syringe can be used
to inject the ink into the channels to allow for an even distribution throughout
the structure. Alternatively, a vacuum can be used to draw the ink through the
microfluidic network.
In step
207 photolithography, the circuit lines are created using photolithography.
Photoresist is spun onto the flexible polymer substrate and patterned, exposing
the underlying flexible polymer substrate layer in regions where the conductive
ink is to be applied. The conductive ink is then spread onto the flexible polymer
substrate. After curing, the photoresist is removed in acetone, lifting off the
undesired conductive ink. This process can be replicated until the desired levels
are completed.
In step
208 a stamp is used to place the ink in a desired pattern on layers
of PDMS. The stamp can be placed in contact with an entire 3-dimensional object,
such as a rod, in a single step. The stamp can also be used to pattern the inside
of a tube or rolled over a surface to form a continuous pattern. The stamp may
also be used for fluidic patterning by flowing material through channels defined
by raised and recessed portions in the surface of the stamp as it contacts the
flexible polymer substrate. The stamp may be used to deposit self-assembled monolayers,
biological materials, metals, polymers, ceramics, or a variety of other materials.
Referring now to FIG. 3, another embodiment of a system constructed in
accordance with the present invention is illustrated. This embodiment is generally
designated by the reference numeral
300. Integrated Microsystems are expected
to play an increasingly important role in Homeland Security. Examples of such integrated
microsystems include: microfluidic systems for chem/bio threat detection, distributed
sensors for tracking terrorist activities, radiation detectors, and cargo container
monitoring devices. These Integrated microsystems require small, low cost, rugged,
field-operable devices. Deployable sensors with wireless communication capability
are required for numerous counter-terrorism and intelligence applications. Examples
include monitoring cargo shipments, tracking troop, individual personnel, and vehicle
movement, and detecting chemical and biological signatures associated with various
threats. These sensor modules must meet several requirements for widespread deployment.
They need to be inexpensive, rugged for air-drop deployment and abusive conditions,
inconspicuous, able to withstand severe environmental factors (temperature extremes,
water submersion), and self-sufficient (integrated power, electronics, sensing,
and communications).
The embodiment
300 comprises a PDMS body
301, an optical sensor
302, a microfluidic channel
303, an antenna
304, a MEMS sensor
305, and an
Application-
Specific
Integrated
Circuit (ASIC)
307.
The optical sensor
302, microfluidic channel
303, antenna
304,
MEMS sensor
305, and
Application-
Specific
Integrated
Circuit (ASIC)
307
are operatively connected to the PDMS body
301. Metal traces circuits
306
are integrated into the PDMS body
301 that connect the optical sensor
302,
microfluidic channel
303, antenna
304, MEMS sensor
305, and
Application-
Specific
Integrated
Circuit (ASIC)
307.
The metal traces circuits
306 are integrated into the PDMS body
301
by various methods. In one embodiment the metal traces circuits
306 are
integrated into the PDMS body
301 by applying conductive ink to the PDMS
body
301. In another embodiment the metal traces circuits
306 are
integrated into the PDMS body
301 by producing three-dimensional microfluidic
channels in the flexible polymer substrate and filling the three-dimensional microfluidic
channels with the conductive ink. The conductive ink cured to produce the circuit
lines. In another embodiment the three-dimensional microfluidic channels are filled
with the conductive ink by injecting the conductive ink into the three-dimensional
microfluidic channels. In another embodiment the three-dimensional microfluidic
channels are filled with the conductive ink by injecting the conductive ink into
the three-dimensional microfluidic channel using a syringe. In another embodiment
the three-dimensional microfluidic channels are filled with the conductive ink
by injecting the conductive ink into the three-dimensional microfluidic channels
using a vacuum to draw the conductive ink through the three-dimensional microfluidic channels.
In another embodiment the metal traces circuits
306 are integrated into
the PDMS body
301 by applying conductive ink to the flexible polymer substrate
using a stamp to place the conductive ink in a desired pattern on the flexible
polymer substrate. In another embodiment the metal traces circuits
306 are
integrated into the PDMS body
301 by applying conductive ink to the flexible
polymer substrate using photolithography. In another embodiment the metal traces
circuits
306 are integrated into the PDMS body
301 by spreading the
conductive ink onto the flexible polymer substrate. In another embodiment the metal
traces circuits
306 are integrated into the PDMS body
301 by spreading
the conductive ink onto the flexible polymer substrate by spin-coating.
In another embodiment the metal traces circuits
306 are integrated into
the PDMS body
301 by spreading the conductive ink onto the flexible polymer
substrate by spraying. In another embodiment the metal traces circuits
306
are integrated into the PDMS body
301 by screen printing. In another embodiment
the screen printing uses a permeable screen mesh. In another embodiment the screen
printing uses a permeable screen mesh of monofilament polyester. In another embodiment
the screen printing uses a permeable screen mesh of stainless steel.
In another embodiment the screen printing uses a screen mesh of polyamide. In
another embodiment the screen printing uses a mechanical stencil of a direct type.
In another embodiment the screen printing uses a mechanical stencil of an indirect
type. In another embodiment the screen printing uses a photomechanical stencil
of a direct type. In another embodiment the screen printing uses a photomechanical
stencil of an indirect type. In another embodiment the screen printing uses screen
printed interconnect transfers. In another embodiment the screen printing uses
conductive ink screen printed onto a carrier backing material. In another embodiment
the carrier backing material is mylar. In another embodiment the carrier backing
material is Kapton.
In another embodiment the metal traces circuits
306 are integrated into
the PDMS body
301 by applying conductive ink to the PDMS body
301
and the conductive ink is cured and transferred in a decal fashion onto the flexible
polymer substrate. In another embodiment the metal traces circuits
306 are
integrated into the PDMS body
301 by applying conductive ink to the PDMS
body
301 and the conductive ink is cured and transferred in a decal fashion
onto the flexible polymer substrate using multilple conductive ink transfer decals
with fiducial alignment marks to complete multiple interconnect routing levels.
The embodiment
300 comprises a polymer-based platform that will enable
the development of hybrid microsystems with integrated sensors, electronics, optical
elements, power, and microfluidics. The platform is capable of incorporating off-the-shelf
components as well as custom fabricated devices, and features a low cost packaging
approach. Polydimethylsiloxane (PDMS) serves as the integration backbone, with
microfluidic structures molded into the silicone polymer, and other components
such as silicon sensors and circuits directly bonded to the PDMS, forming a leak-proof
seal. Electrical traces are patterned on the PDMS to interconnect the various components.
The ACIC chip
307 and the other components are irreversibly bonded to the
PDMS substrate
301 to make electrical contact to the metal traces
306
and seal the device
300, protecting active elements from the environment.
The antenna
304 facilitates communication with a remote receiver.
Referring now to FIGS. 4A and 4B, an embodiment of an alignment system
used in screen printing multiple layers of metalization is illustrated. The system
is designated generally by the reference numeral
400 and is includes a transparent
hard surface and spacers calibrated to suspend the transparent surface a few microns
above the substrate to be printed. In one embodiment the spacers are variable in
height to accommodate arbitrary substrate thickness. FIG. 4A is a side view and
FIG. 4B is a plan view of the alignment system
400. FIGS. 4A and 4B depicts
the alignment process.
Metalization required for integrated polymer microsystems are either
single level (layer) or multiple levels depending on the complexity of the device.
As in conventional photolithography, an electrically insulating layer is applied
between each layer of metalization. The first layer is often placed arbitrarily
on the substrate while subsequent layers require registration of features to the
first base layer. Typical screen printing emulsions are fairly opaque and are by
nature of the machine hardware between the operator and the substrate making visible
alignment extremely difficult if not impossible.
As shown in FIG. 4A, the alignment system
400 comprises a number of components
and elements of the device being produced. The following elements and components
are included: a spacer
401, a transparent surface
402 such as glass
or rigid plastic such as Plexiglas, printing screen
403, substrate
404,
thin substrate positioner/carrier, first metal layer
406, fixed placement
guide
407, vacuum table
408, and screen alignment on transparent
surface transfer.
The first alignment step is to roughly position the alignment apparatus on the
vacuum table
408 such that it is oriented to the pattern on the printing
screen. A placement guide is then fixed to the table
408 for subsequent
removal and exact repositioning of the alignment apparatus. Next ink is screen
printed onto the transparent surface producing a registration pattern for subsequent
alignment of the substrate. The substrate
404 is placed on a piece of Mylar,
Kapton, or other thin material, which is used as a carrier and positioner
405.
The carrier is perforated to permit vacuum pull down on the substrate. The substrate
is then positioned under the transparent surface
402 and aligned to features
on the substrate surface such as first or subsequent layers of metalization. After
the substrate is properly registered to the pattern on the transparent surface
the alignment apparatus is removed from the table and the vacuum is turn on securing
the substrate.
The substrate is now ready for screen printing of an aligned pattern. After printing
the substrate is removed and the alignment apparatus is replaced on the surface
accurately as it is pushed up against the placement guide. Now another substrate
is placed on the carrier and aligned as detailed above. The entire process is repeated
for each subsequent substrate to be printed.
While the invention may be susceptible to various modifications and alternative
forms, specific embodiments have been shown by way of example in the drawings and
have been described in detail herein. However, it should be understood that the
invention is not intended to be limited to the particular forms disclosed. Rather,
the invention is to cover all modifications, equivalents, and alternatives falling
within the spirit and scope of the invention as defined by the following appended claims.
*
