U.S. patent application number 12/728968 was filed with the patent office on 2010-07-08 for multifunctional conducting polymer structures.
This patent application is currently assigned to Santa Fe Science and Technology, Inc.. Invention is credited to Benjamin R. Mattes, Baohua Qi.
Application Number | 20100170886 12/728968 |
Document ID | / |
Family ID | 34115562 |
Filed Date | 2010-07-08 |
United States Patent
Application |
20100170886 |
Kind Code |
A1 |
Qi; Baohua ; et al. |
July 8, 2010 |
MULTIFUNCTIONAL CONDUCTING POLYMER STRUCTURES
Abstract
The present invention includes the use of conducting polymers as
sensors in distributed sensing systems, as sensors and operating
elements in multifunctional devices, and for conducting-polymer
based multifunctional sensing fabrics suitable for monitoring
humidity, breath, heart rate, blood (location of wounds), blood
pressure, skin temperature, weight and movement, in a wearable,
electronic embedded sensor system, as examples. A fabric comprising
conducting polyaniline fibers that can be used to distribute energy
for resistive heating as well as for sensing the fabric temperature
is described as an example of a multifunctional sensing fabric.
Inventors: |
Qi; Baohua; (Albuquerque,
NM) ; Mattes; Benjamin R.; (Santa Fe, NM) |
Correspondence
Address: |
COCHRAN FREUND & YOUNG LLC
2026 CARIBOU DR, SUITE 201
FORT COLLINS
CO
80525
US
|
Assignee: |
Santa Fe Science and Technology,
Inc.
Santa Fe
NM
|
Family ID: |
34115562 |
Appl. No.: |
12/728968 |
Filed: |
March 22, 2010 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
12331010 |
Dec 9, 2008 |
7683643 |
|
|
12728968 |
|
|
|
|
10910169 |
Aug 2, 2004 |
7463040 |
|
|
12331010 |
|
|
|
|
60491885 |
Aug 1, 2003 |
|
|
|
Current U.S.
Class: |
219/482 ;
324/693 |
Current CPC
Class: |
H01B 1/124 20130101 |
Class at
Publication: |
219/482 ;
324/693 |
International
Class: |
H05B 3/02 20060101
H05B003/02; G01R 27/08 20060101 G01R027/08 |
Goverment Interests
STATEMENT REGARDING FEDERAL RIGHTS
[0002] This invention was made with government support under
Contract No. MDA972-99-C-0004 awarded by the U.S. Defense Advance
Research Projects Agency to Santa Fe Science and Technology, Inc.,
Santa Fe, N. Mex. 87507. The government has certain rights in the
invention.
Claims
1. Multifunctional device comprising in combination: (a) a
conducting polymer element having the value of a physical property
responsive to a condition to which said element is exposed, said
element being capable of changing the condition in response to a
stimulus external to said element; (b) means for measuring the
value of the physical property and generating a signal in response
thereto; and (c) means for receiving the signal from said value
measuring means, for generating a stimulus effective for
maintaining the condition at a chosen value or changing the
condition to a new value and for applying the stimulus to said
element.
2. The multifunctional device as described in claim 1, wherein said
conducting polymer element comprises polyanline.
3. The multifunctional device as described in claim 1, wherein the
condition is temperature, the physical property of said element is
resistivity, and the stimulus is electric current.
4. The multifunctional device as described in claim 1, wherein said
element comprises at least one polyaniline fiber.
5. The multifunctional device as described in claim 4, wherein said
at least one polyaniline fiber is woven, knitted, stitched, or
braided into a fabric comprising non-conducting fibers.
6. Apparatus for measuring subject status, comprising in
combination: (a) a first plurality of substantially parallel,
spaced-apart, electrically conducting polymer fibers defining a
first surface; (b) a second plurality of substantially parallel,
spaced-apart, electrically conducting polymer fibers defining a
second surface, such that the first surface and the second surface
are coextensive; (c) means for electrically isolating said first
plurality of polymer fibers from said second plurality of polymer
fibers; (d) means for applying an electrical signal to at least one
polymer fiber of said first plurality of polymer fibers; (e) means
for detecting an electrical signal on at least one polymer fiber of
said second plurality of polymer fibers; and (f) means for
measuring the time dependence of the resistance of at least one
polymer fiber from said first plurality of polymer fibers, or from
said second plurality of polymer fibers.
7. The apparatus as described in claim 6, wherein said means for
applying an electrical signal to said at least one polymer fiber is
adapted to repeatedly apply the electrical signal to said at least
one polymer fiber in said first plurality of polymer fibers in a
first chosen order during a first chosen period, whereby
substantially all of said at least one polymer fibers in turn
receive a signal during the chosen period.
8. The apparatus as described in claim 7, wherein said means for
detecting an electrical signal on said at least one polymer fiber
is adapted to repeatedly sample the electrical signal on said at
least one polymer fiber in said second plurality of polymer fibers
in a second chosen order during a second chosen period, whereby
substantially all of said at least one polymer fibers in said
second plurality of polymer fibers are sampled in turn.
9. The apparatus as described in claim 6, wherein said means for
measuring the time dependence of the resistance of at least one
polymer fiber from said first plurality of polymer fibers, or from
said second plurality of polymer fibers is adapted to repeatedly
sample the resistance on said at least one polymer fiber from said
first plurality of polymer fibers, or from said second plurality of
fibers in a third chosen order during a third chosen period,
whereby substantially all of said at least one polymer fibers in
said first plurality of polymer fibers, or in said second plurality
of fibers are sampled in turn.
10. The apparatus as described in claim 6, wherein said first
plurality of electrically conducting polymer fibers and said second
plurality of electrically conducting polymer fibers comprise
polyaniline fibers.
11. The apparatus as described in claim 10, wherein said
polyaniline fibers are woven, knitted, stitched, or braided into a
fabric comprising non-conducting fibers.
12. The apparatus as described in claim 6, wherein said subject
status comprises subject breathing and subject bleeding.
13. Apparatus for heating, comprising in combination: (a) at least
one conducting polymer fiber; (b) means for applying electric
current to said at least one conducting polymer fiber; and (c)
means for measuring the resistance of said at least one polymer
fiber, such that the temperature of said fiber can be
determined.
14. The apparatus as described in claim 13, further comprising
feedback means for controlling said electric current applying means
in response to the resistance measured by said resistance measuring
means, whereby the temperature of said conducting polymer fiber is
maintained at a chosen temperature.
15. The apparatus as described in claim 13, wherein said conducting
polymer fiber comprises polyaniline.
16. The apparatus as described in claim 15, wherein said
polyaniline fiber is woven, knitted, stitched, or braided into a
fabric comprising non-conducting fibers.
17. A method for heating, comprising the steps of: (a) applying
electric current to at least one conducting polymer fiber; and (b)
measuring the resistance of the at least one polymer fiber, such
that the temperature of the fiber can be determined.
18. The method as described in claim 17, further comprising the
step of controlling said electric current in response to the
resistance measured in said step of measuring the resistance with a
feedback system, whereby the temperature of said conducting polymer
fiber is maintained at a chosen temperature.
19. The method as described in claim 17, wherein said conducting
polymer fiber comprises polyaniline.
20. The method as described in claim 19, wherein said polyaniline
fiber is woven, knitted, stitched, or braided into a fabric
comprising non-conducting fibers.
Description
RELATED CASES
[0001] This application is a Divisional of patent application Ser.
No. 12/331,010 filed on Dec. 9, 2008, which was a Divisional of
patent application Ser. No. 10/910,169 filed on Aug. 2, 2004 which
issued as U.S. Pat. No. 7,463,040 on Dec. 9, 2008, and claimed the
benefit of Provisional Patent Application Ser. No. 60/491,885, for
"Multifunctional Conducting Polymer Structures" filed on Aug. 1,
2003, the teachings of which were incorporated by reference
therein.
FIELD OF THE INVENTION
[0003] The present invention relates generally to conducting
polymer devices and, more particularly, to the use of conducting
polymer structures as multifunctional devices and distributed
sensors.
BACKGROUND OF THE INVENTION
[0004] The many types and forms of textile materials have one thing
in common: almost all such fabrics are passive, and do not respond
or interact by active human control with the environment into which
they are placed. Typically, technical textiles are prepared from
low volume, high value specialty synthetic fibers, while wearable
(fashion) textiles are prepared from high volume low value natural
or synthetic fibers. If electronic function could be integrated
with technical or wearable textiles, then a new generation of
devices would be possible. However, suitable conducting and
semi-conducting textile fibers are scarce. There is therefore, a
need for fibers that conduct electricity like a metal or an
inorganic semiconductor, while simultaneously being compatible with
conventional textile processing equipment. Such fiber must be
mechanically strong and flexible, yet also be environmentally
stable throughout the lifetime of the fabric.
[0005] Multifunctional electronic fabrics (Smart Fabrics and
Interactive Textiles) can potentially revolutionize the way in
which people interact with their daily environment. However,
electronic devices would have to be brought into close proximity to
the human body. Environmental stimuli (data) would be sensed or
detected and collected through a variety of sensors at different
locations of the fabric. The data collected from the body (or
environment) would then be sent to a signal-processing unit
(controller) for interpretation and, after a controlled response is
achieved, information would be sent to other areas of the fabric
(or an external device) to achieve a desired outcome from a
functional device.
[0006] Organic semiconductors, variously called .pi.-conjugated
polymers, conducting polymers, or synthetic metals, are inherently
semi-conductive due to .pi.-conjugation between carbon atoms along
the polymer backbone. Their structure contains a one-dimensional
organic backbone based on the alternation of single and double
bonds, which enables electrical conduction following n.sup.- or
p.sup.+ type doping. Such materials offer advantages for sensor
technologies, including the ability to tailor structure and
properties, relatively low cost, and simple fabrication techniques;
for example, they can be coated onto various types of substrates.
These materials also have properties traditionally associated with
other inorganic materials, including light absorption and emission;
electrical conductivity; humidity, temperature, and pressure
sensitivity; and electrochromic behavior. Unlike other conductive
fiber materials that have been successfully woven by textile
manufacturing equipment, such as metal wire (heavy, fabric, not
washable), carbon or metal-filled plastic fiber (mechanical
properties degrade with increased loading), graphite fiber (too
stiff and brittle), and piezoelectric fiber (poorly conducting),
conducting polymer fibers such as polyaniline are strong (strength
modulus 2-6 GPa, tenacity 80-300 MPa), light weight (1.5
g/cm.sup.3), flexible (between 3% and 20% elongation), and highly
conductive (300-1000 S/cm), making them suitable for weaving,
knitting, stitching, and braiding.
[0007] Accordingly, it is an object of the present invention to
provide wearable electronic textiles containing embedded wired,
wireless and/or hybrid sensors, and distributed sensor networks
(DSN) for sensing humidity, temperature, applied load (stress) and
dimensional changes (strain), as examples.
[0008] Another object of the present invention is to provide sensor
and DSN fabric for monitoring breathing rate, heart rate, blood
emission (wound location), blood pressure, humidity, weight,
movement, and skin temperature (for predicting the onset of
hyperthermia and hypothermia).
[0009] Yet another object of the invention is to provide fabric
having multifunctional capability.
[0010] Additional objects, advantages and novel features of the
invention will be set forth in part in the description which
follows, and in part will become apparent to those skilled in the
art upon examination of the following or may be learned by practice
of the invention. The objects and advantages of the invention may
be realized and attained by means of the instrumentalities and
combinations particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
[0011] To achieve the foregoing and other objects, and in
accordance with the purposes of the present invention as embodied
and broadly described herein, the multifunctional device hereof
includes: a conducting polymer element having a physical property
the value of which is responsive to a condition to which the
element is exposed, the element being capable of conducting
electrical signals and/or changing the condition in response to a
stimulus external to the element; means for measuring the value of
the physical property and for generating a signal in response
thereto; and means for receiving the signal from the measuring
means and for maintaining the condition at a chosen value or
changing the condition by generating a stimulus effective for
changing the condition and applying the stimulus to the
element.
[0012] In another aspect of the present invention and in accordance
with its objects and purposes, the apparatus for heating hereof
includes: (a) at least one conducting polymer fiber; (b) means for
applying electric current to the at least one conducting polymer
fiber; and (c) means for measuring the resistance of the at least
one polymer fiber, such that the fiber temperature can be
determined.
[0013] In yet another aspect of the present invention and in
accordance with its objects and purposes, the apparatus for
providing humidity hereof, includes: (a) at least one conducting
polymer fiber; (b) means for applying electric current to the at
least one conducting polymer fiber effective for controlling the
amount of water absorbed thereon; and (c) means for measuring the
resistance of the at least one polymer fiber, such that the
relative humidity to which the fiber is exposed can be
determined.
[0014] In yet a further aspect of the present invention and in
accordance with its objects and purposes, the method for heating
hereof includes the steps of: (a) applying electric current to at
least one conducting polymer fiber; and (b) measuring the
resistance of the at least one polymer fiber, such that the
temperature of the fiber can be determined.
[0015] In still another aspect of the present invention and in
accordance with its objects and purposes, the method for providing
humidity hereof includes the steps of: (a) applying electric
current to at least one conducting polymer fiber effective for
controlling the amount of water absorbed thereon; and (b) measuring
the resistance of the at least one polymer fiber, such that the
relative humidity to which the fiber is exposed can be
determined.
[0016] Benefits and advantages of the multifunction device of the
present invention include light weight, compact design, the
capability of large area sensing, and massive redundancy of the
sensor system which leads to improved reliability; that is,
conducting polymer fibers function both as sensors and as
conductors (wires), which enables area sensing since the entire
fiber (or fabric) functions as a sensor. Area sensing gives rise to
the redundant nature since, if a portion of a sensor system
(fabric) fails, other parts of the system may still be able to
acquire the required information and perform the function.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The accompanying drawings, which are incorporated in and
form a part of the specification, illustrate several embodiments of
the present invention and, together with the description, serve to
explain the principles of the invention. In the drawings:
[0018] FIG. 1 is a graph of the DC conductivity for a polyaniline
fiber as a function of temperature.
[0019] FIG. 2 is a graph of the change in temperature of a 12 mm
long, 95 .mu.m diameter polyaniline fiber resulting from resistive
heating as a function of applied voltage, where the base
temperature is 22.9.degree. C.
[0020] FIG. 3 is a graph of the resistance of a polyaniline fiber
(length: 136.0 mm; diameter: 84 m) as a function of percent
relative humidity at room temperature (26.5.degree.
C..+-.0.5.degree. C.).
[0021] FIG. 4a is a graph of the resistance as a function of time
for an overloading voltage (4.5V) applied to a polyaniline fiber
having a length of 12.0 mm and a diameter 95 .mu.m, while FIG. 4b
is a graph of the temperature change as a function of time for this
fiber, where the base temperature is 22.9.degree. C.
[0022] FIG. 5 is a graph of the resistance of a polyaniline fiber
as a function of applied force for a polyaniline fiber having a
diameter of 118 .mu.m and a length of 60 mm; the temperature was
24.2.degree. C., and the relative humidity was 20%.
[0023] FIG. 6a is a photograph of a 40 denier conducting
polyaniline monofilament (dark fibers) knitted into a fabric with
insulating nylon yarn (light fibers); FIG. 6b shows 2-D tape braid
composed entirely of 40 denier conducting polyaniline monofilament
fibers; and FIG. 6c shows a tubular braid of 40 denier conducting
monofilament polyaniline fiber.
[0024] FIG. 7a shows the percent change of resistance of the
polyaniline monofilament knitted into the fabric shown in FIG. 6
hereof as a function of the percent extension of the fabric, while
FIG. 7b shows the percent change of resistance thereof as a
function of applied force (N).
[0025] FIG. 8a shows a schematic representation of an apparatus for
detecting the presence of an electrolyte, such as blood, and its
location on a fabric made in accordance with the teachings of the
present invention, while simultaneously resistively heating a
wearer of the fabric; FIG. 8b shows signals observed on a set of
substantially parallel fibers when a voltage stimulus is applied to
a second set of substantially parallel fibers perpendicular
thereto; and FIG. 8c shows a block diagram of the control module
for the apparatus shown in FIG. 8a.
[0026] FIGS. 9a-9c show schematic representations of several
embodiments of apparatus for sensing changes in shape; while FIG.
9d shows a block diagram of the control module therefor.
[0027] FIG. 10a shows a schematic representation of a touch sensor
embodiment of the present invention, while FIG. 10b shows a graph
of the resistance of the sensor as a function of sensor
bending.
[0028] FIG. 11 shows a schematic representation of an embodiment of
the present invention showing a conducting polymer heating element
capable of generating heat when current is passed therethrough, the
resistivity of the heating element varying with temperature such
that from the measurement of the resistivity of the element and the
adjustment of the applied current or voltage, a chosen temperature
can be maintained.
DETAILED DESCRIPTION
[0029] Wearable interfaces between electronic devices and people
are achieved using Smart Fabrics and Interactive Textiles (SFIT),
where functional devices are embedded into wearable garments. A
SFIT device, as used herein, includes the following: (a) a fabric
that contains electrically conductive polymer fiber (or yarn)
interlaced (by weaving, knitting, stitching, or braiding) with a
non-conductive structural fiber (or yarn) that is capable of
relaying electrical signals from one location of the fabric to
another; (b) a data acquisition or sensing element (DAE) that
processes changes in electrical signals from the conductive fiber
elements of the fabric; and (c) a controller that receives input
from the sensing elements, and generates an electrical output
directed to functional devices in a controlled fashion (set
points), as collected from the DAE, to achieve the desired outcome.
Additional microelectronic hardware may be incorporated for data
transmission; for example, radiofrequency transmission via
Bluetooth or WIFI, and reception (computer) for data processing.
Due to their multifunctional design, SFIT fabrics are wearable
devices that are flexible and comfortable to wear.
[0030] Both the monitoring of body kinematics and health (including
vital signs detection), would benefit from the implementation of
wearable sensorized systems. In particular, garments with strain
and stress sensing capabilities would enable the tracking and
accurate determination of kinematic variables such as walking,
jumping, and landing, as examples. The integration into
skin-adherent clothes of several kinds of biosensors for health
monitoring would permit daily health promotion and disease
prevention through a continuous, personalized and self-detection of
vital signs and physiological variables.
[0031] Besides sensors, the comfortable embedding into textile
substrates of smart actuators represents a further potentially
useful tool for rehabilitation. Actuators may provide mechanical
support and motion for lost or impaired motor functions for
physiotherapeutic restoration. These actions could be performed
either by following predefined tasks or by exploiting the strain
and stress information produced by co-integrated sensors. The
active support offered by wearable actuators could also improve
sports training techniques or prevent risks related to abnormal
stress distributions and overloading.
[0032] Sensors and actuators used in textiles may be electrically
powered and controlled by power and electronic devices also
advantageously embedded in the fabrics. The integration of active
electronic components would enable the implementation of
closed-loop controls for the system. Furthermore, the possibility
of simultaneously monitoring a set of physiological signals and
variables and processing and transmitting data offers a capability
to support health professionals for remote assistance. Home care of
sick or elderly persons, or treatment of individuals in extreme
conditions such as soldiers or astronauts, are examples of possible
fields of application.
[0033] Wearable multifunctional textiles may be useful for wearable
wireless communication systems (integration into clothes of
resources for the transmission of information; that is, earphones,
microphones or entire mobile phones); personnel telecontrol (for
example, localization and tracking of persons through local
networks or the global positioning system (GPS)), tele-assistance
(for example, embedding accidental fall sensors for elders and
automatic help request sensors into garments); ergonomics (for
example, integration of devices for comfort and safety); and
virtual-augmented reality (for example, simulation wearable systems
for professional training and interactive entertainment).
[0034] As examples of the above applications, the present invention
includes the use of conducting polymers as sensors in distributed
sensing systems, as sensors and operating elements in
multifunctional devices, and conducting-polymer based
multifunctional sensing fabrics suitable for monitoring humidity,
breath, heart rate, blood emission (location of wounds), blood
pressure, skin temperature, weight and movement, in a wearable,
electronic sensor system, as examples. The use of conducting
polymers for such sensing functions, in addition to actuation,
computation and electrical energy generation/storage offers
advantages passive properties in terms of mechanical flexibility
and ease of processing, as well as superiority over inorganic
materials used for such functions.
[0035] There are many ways to layout multi-functionality in the
textile format. For certain applications a fabric or a braided
structure may consist entirely of the conducting polymer fiber
(See, e.g., FIGS. 6a and 6b, where 2-D braided tape or 3-D tubular
braid are respectively shown). In other instances and applications,
it may be desired to co-mingle the conducting polymer fiber (or
yarn) with non-conducting fiber structural or insulating elements
(See, e.g., FIG. 6a, where a conducting polyaniline thread is
co-knitted with an insulating Nylon yarn.). In any case, those
skilled in the art will recognize that the primary methods for
creating multi-functional structures include weaving, knitting,
stitching, or braiding.
[0036] Woven structures can be divided into two principal
categories: simple structures and compound structures. In simple
structures, the ends (warp) and the picks (weft) intersect one
another at right angles and in the fabric are respectively parallel
with each other. In such constructions, there is only one series of
ends and one series of picks, and all threads are equally
responsible for both the utility (performance) of a fabric and its
aesthetic appeal. Compound structures may have more than one series
of ends or picks, some of which may be responsible for the "body"
of the fabric, such as ground yarns, while others may be employed
entirely for ornamental purposes such as "figuring" or "face"
yarns. Pile surface constructions have some threads projecting out
at right angles to the general plane of the fabric.
[0037] There are three types of weaves: plain, twill and satin. All
variations may include elements of one or more basic weaves in each
cloth. In a plain weave, the threads are interlaced in alternate
order, and if the warp and weft threads are similar in thickness
and number per unit space, the two series of threads bend about
equally. The twill order of interlacing causes diagonal lines to be
formed in the cloth. These weaves are employed for the purpose of
ornamentation and to enable a cloth of greater weight, close
setting, and better draping quality to be formed than can be
produced using similar yarns in plain weave. The surface of a satin
weave consists either of a weft or warp float, as in the repeat of
a weave each thread of one series passes over all but one thread of
the other series. Satin weaves have a high degree of smoothness and
luster without any prominent weave features. The present invention
includes biaxial woven, high modulus woven, multilayer woven, and
triaxial woven fabric structures.
[0038] Placement of conducting polymer fibers such as polyaniline
to create multifunctional structures can be achieved by knitting
(See FIGS. 6a and 6b). Knitting is the process of constructing a
fabric by forming loops of yarn with needles and drawing other new
loops through those previously formed, and includes the process of
making a fabric on more than one needle by interloping a thread (or
yarn) or several parallel threads (or yarns). There are two
categories into which all specific types fall: warp knitting and
weft knitting. Warp knitting has two basic types: Tricot and
Raschel. Weft knitting has four basic knit structures: plain, rib,
purl, and interlock. Other embodiments of the present invention
include: weft knit, warp knit, weft knit laid in weft, weft knit
laid in warp, weft knit laid in weft and warp, weft inserted warp
knit, weft inserted warp knit laid in warp, multifunctional
structures.
[0039] Placement of conducting polymer fibers such as polyaniline
to create multifunctional structures can be achieved by stitching.
Stitching is a method for interlacing two (or many) separate
textile parts together. Stitching allows for accurate placement of
interconnects, for creating superficial circuits from conducting
polymer thread, and for attaching electronic components to textile
surfaces. If stitching large areas or three-dimensional
complex-shaped structures are desired, then one-side stitching
techniques may be successfully utilized. Since the work piece can
be accessed from one side only, stitching of complicated structures
is not limited by the design or the size of the stitching
machine.
[0040] A wide range of stitch geometries are possible at various
stitch densities. Besides the conventional double-lock stitch, two
different techniques for one-side stitching are available. The
two-needle one-side simple chain stitching head produces a
double-line seam; the work piece is penetrated by the stitching
thread at different inserting angles. Where local reinforcement or
localized interconnects are needed, a tufting head can be used
which allows insertion of the stitching thread at various angles
and under the lowest possible thread tensions.
[0041] Placement of conducting polymer fibers such as polyaniline
to create multifunctional structures can be achieved by braiding.
Braided structures are intertwined fiber assemblies known for their
torsional stability, high level of formability, and net shape
capability. Braided structures can assume a linear geometry or a
2-D planar geometry, as in tapes (FIG. 6b), and 3-D body of
revolution including tubular structure (FIG. 6c) or solid net-shape
structures. Thus braided structures are ideal for energy
transmitters such as cable or motion generators, as in linear 2-D
and 3-D actuators, as well as for composite stiffening members for
antenna disk or multi-layer interconnects. Other embodiments of the
present invention include: tubular braid, tubular braid laid in
warp, flat braid, flat braid laid in warp, square braid, square
braid laid in warp, 3D braid, and 3-D braid laid in warp.
[0042] Textile structures having different functions may have
woven, stitched or braided conducting polymer fibers strategically
placed throughout the fabric. A connector bus is used for internal
communication among the functional fabrics, and for the data link
between the embedded sensor system and a central computer. Such a
structure has the advantage of being readily upgraded or changed by
changing the functional fabrics, while not decreasing the
reliability of the system.
[0043] As an example, a fabric comprising conducting polyaniline
fibers can be used to distribute energy for resistive heating as
well as for sensing the fabric temperature. An additional advantage
of such a polyaniline fiber structure is that when too high a
voltage or current is applied to the fibers, it has been found that
the fibers lose their conductivity between 40.degree. C. and
60.degree. C., much below the decomposition temperature of the
fibers (between about 150.degree. C. and 250.degree. C.);
therefore, if the temperature control system fails, the heating
fabric will not burn the skin.
[0044] Although polyaniline used for practice of the present
invention was produced from polymerization of unsubstituted
aniline, the term polyaniline as used herein includes the following
polyanilines which are expected to perform in a similar manner.
Polyanilines suitable for use in accordance with the present
invention are homopolymers and copolymers derived from the
polymerization of unsubstituted or substituted anilines of the
form:
##STR00001##
where n is an integer between 0 and 2; m is an integer between 3
and 5, such that n+m=5; R.sub.1 is selected so as to be the same or
different at each occurrence and is selected from the group
consisting of aryl-, alkyl-, alkenyl-, alkylthio- and
alkoxy-moieties having between 1 and about 30 carbon atoms, cyano-,
halo-, acid functional groups, such as those from sulfonic acid,
carboxylic acid, phosphonic acid, phosphoric acid, phosphinic acid,
boric acid, sulfinic acid and derivatives thereof, such as salts,
esters, and the like; amino-, alkylamino-, dialkylamino-,
arylamino-, hydroxyl-, diarylamino-, and alkylarylamino-moieties;
or alkyl, aryl, alkenyl, alkylthio or alkoxy substituted with one
or more acid functional groups, such as sulfonic acid, carboxylic
acid, phosphonic acid, phosphoric acid, phosphinic acid, boric
acid, sulfinic acid and derivatives thereof, such as salts, esters,
and the like. R.sub.2 is the same or different at each occurrence
and, is either one of the R.sub.1 substituents or hydrogen.
[0045] Polyanilines suitable for use in this invention are
generally those which include the following repeat units or a
combination thereof having various ratios of these repeat units in
the polyaniline backbone:
##STR00002##
As an example:
##STR00003##
where x represents that fraction of the reduced repeat units in the
polymer backbone and 7 represents at fraction of the oxidized
repeat units in the polymer backbone, such that x+y=1; and z is an
integer equal to or greater than about 20. For the polymer in its
emeraldine base oxidation state, x=0.5 and y=0.5.
[0046] I. Preparation of Conducting Polymer Fibers:
[0047] The conducting polymer fibers and fabrics used to illustrate
the present invention were prepared as follows:
[0048] A. Synthesis of High Molecular-Weight Polyaniline:
[0049] Water (6,470 g) was first added to a 50 L jacketed reaction
vessel fitted with mechanical stirrer. Phosphoric acid (15,530 g)
was then added to the water, with stirring, to give a 60 mass %
phosphoric acid solution. Aniline (1,071 g, 11.5 moles) was added
to the reaction vessel over a 1 h period. The stirred aniline
phosphate was then cooled to -35.0.degree. C. by passing a cooled
50/50 by mass, methanol/water mixture through the vessel jacket.
Ammonium persulfate oxidant (3,280 g, 14.37 moles) was first
dissolved in water (5,920 g), and the resulting solution was added
to the cooled, stirred reaction mixture at a constant rate over a
30 h period. The temperature of the reaction mixture was maintained
at -35.0.+-.1.5.degree. C. during the duration of the reaction.
[0050] The reactants were typically permitted to react for 46 h,
after which the polyaniline precipitate was filtered from the
reaction mixture and washed with about 25 L of water. The wet
polyaniline filter cake was then mixed with a solution of 800 mL of
28% ammonium hydroxide solution mixed with 20 L of water and
stirred for 1 h, after which the pH of the suspension was measured
to be 9.4, to convert the as-synthesized polyaniline from its
conductive, emeraldine salt oxidation state to its emeraldine base
oxidation state (PANI-EB).
[0051] The polyaniline slurry was then filtered and the polyaniline
filtrate washed 4 times with 10 L of water per wash, followed by a
washing with 2 L of isopropanol. The resulting polyaniline filter
cake was placed in plastic trays and dried in an oven at 35.degree.
C. until the water content was below 5 mass %. The recovered mass
of dried polyaniline emeraldine base was 974 g (10.7 moles)
corresponding to a yield of 93.4%. The dried powder was sealed in a
plastic bag and stored in a freezer at -18.degree. C. The weight
average molecular weight (M.sub.w) of the powder was determined to
be 280,000 gmol.sup.-1, although M.sub.w values between about
100,000 and about 350,000 gmol.sup.-1 have been obtained using this
synthesis by controlling the reaction temperature between 0 and
-35.degree. C., respectively. Gel permeating chromatograph
molecular weight data was obtained using a 0.02 mass % solution of
EB in NMP containing 0.02 mass % lithium tetrafluoroborate. The
flow rate of the solution was 1 mLmin..sup.-1, and the column
temperature was 60.degree. C. The Waters HR5E column utilized was
calibrated using Polymer Labs PS1 polystyrene standards.
[0052] All reported solutions were made using PANI-EB having a
weight average molecular weight (M.sub.w) of about 300,000
gmol.sup.-1. However, fibers have been successfully produced using
polyaniline having weight average molecular weights between about
90,000 and about 350,000 gmol.sup.-1 (defined as high molecular
weight polyaniline herein). The use of higher molecular weight
polyaniline enables the fibers to survive greater stretch ratios in
the spin line without breaking. High stretch ratios are important
for obtaining fibers having high electrical conductivity, high
modulus and high peak stress.
[0053] B. Fiber Spinning of Spin Solutions Having 6 Mass %
PANI.AMPSA.sub.0.6 in DCAA:
[0054] Polyaniline emeraldine base (84.2 g, 0.93 moles of aniline
repeat units) and 2-acrylamido-2-methyl-1-propanesulfonic acid
(AMPSA, 115.8 g, 0.56 moles) were added to a 2 L plastic vessel
containing a ceramic grinding media. The contents were milled for 2
h, and 1.0 g of water was added to the vessel contents 30 min.
after the milling process was commenced. Dichloroacetic acid (DCAA,
940 g) was placed in a vessel that was maintained at a temperature
between 10 and 15.degree. C.
[0055] A Silverson SL4RT mixer having a duplex head was immersed in
the DCAA and stirred at 1500-2000 rpm. PANI.AMPSA.sub.0.6 powder
(60 g) was added with stirring to the DCAA over a 3 h period to
produce 1 kg of a 6 mass % solution. The temperature of the stirred
solution was kept below 35.degree. C. at all times to prevent
gelling. After the powder addition, the solution was further mixed
for 18 h before being degassed under a dynamic vacuum of .about.50
mbar for 1 h.
[0056] The degassed solution was placed inside of a pressure vessel
and 20 psi of nitrogen gas pressure was applied to the vessel to
direct the solution to a gear pump. The solution was passed through
a 230 .mu.m pore filter prior to entering the gear pump, (Mahr
& Feinpruf) which included 2 interlocking cogs which deliver
0.08 cm.sup.3 of solution per revolution. The gear pump was
adjusted to deliver the spin solution at a rate of 1.3
cm.sup.3min..sup.-1. The solution was then passed through 230 and
140 .mu.m pore filters before entering a 250 .mu.m diameter
spinneret (l/d=4). The spinneret was immersed in an ethyl acetate
coagulation bath (wet spinning), and the nascent fiber was passed
through the coagulation bath for about 1 m before being taken up on
a pair of rotating (12.0 rpm; 6.2 mmin..sup.-1.), 16.5 cm diameter
godet drums immersed in a 1 M solution of phosphoric acid.
[0057] The fiber was then passed through a 1.2 m long heat tube
maintained at a temperature of 90.+-.10.degree. C. and wound onto a
second godet pair having the same diameter and the first pair, and
turning at 15.6 rpm (8.1 mmin..sup.-1), thereby stretching the
fiber with a 1.3:1 stretch ratio. The fiber was then collected on a
15 cm diameter bobbin turning at 18 rpm (8.5 mmin..sup.-1) and
allowed to dry at ambient conditions for several weeks. About one
month later, a section of the fiber was measured and found to have
a diameter of 56.+-.2 .mu.m, a conductivity of 270.+-.30
Scm.sup.-1, a peak stress of 108.+-.9 MPa, a modulus of 4.1.+-.0.3
GPa, and an extension at break of 20.+-.4%.
[0058] C. Fiber Spinning of Spin Solutions Having >6 Mass %
PANI.AMPSA.sub.0.6 in DCAA:
[0059] Solutions having between 7 and 14 mass % PANI.AMPSA.sub.0.6
in DCAA were prepared on the 1 kg scale in accordance with the
procedure set forth hereinbelow. The PANI-EB powder was dried to
achieve the desired individual residual water contents listed in
TABLE 1 under ambient conditions or using a vacuum oven at
approximately 60.degree. C. The water content of the PANI-EB powder
was determined by thermogravimetric analysis (TGA). If the mass %
of water in the PANI-EB powder was found to be lower than the
chosen amount, additional deionized water was added to the powder
prior to preparing the spin solution to achieve the chosen water
content. The percentage water in the spinning solutions was between
0.1 and 0.6 mass %, which corresponds to a water content in the
polyaniline of between 2 and 12 mass %.
[0060] Solution A was prepared by first dissolving 1/2 of the AMPSA
(17.4 g) in the DCAA solvent. The remaining AMPSA (17.4 g) was then
ground with the PANI-EB powder forming a PANI/AMPSA powder mixture,
and added to the DCAA solution in discrete portions with mixing
over a 7 h period. Solutions B, C and D were prepared by dissolving
all of the AMPSA in the DCAA, and adding the PANI-EB powder to the
DCAA solution in discrete portions with mixing over a 5-7 h period.
The total mixing time for each of these solutions is also listed in
TABLE 1 which provides a summary of compositions for PANI.AMPSA
solutions dissolved in DCAA. Other solutions, not reported here,
were prepared by combining the PANI-EB and AMPSA powders using a
ball mill and added to the DCAA in discrete portions. The final
solution properties have been found to be independent of the method
for powder addition, so long as the rate of powder addition of each
portion was chosen to maintain the solution temperature below
35.degree. C. (to avoid gelation).
[0061] As the solutions become more concentrated, the viscosity
thereof increases. This results in additional heat being generated
by viscous dissipation; therefore, the temperature of the mixing
solutions was continuously monitored to ensure that the solution
temperature did not exceed 35.degree. C. Entrapped air resulting
from the mixing process was removed by degassing the solutions
under vacuum at 50 mbar for 1 h before use.
TABLE-US-00001 TABLE 1 Solids % water in % water in Total Max.
Content Scale PANI-EB PANI AMPSA DCAA solution mixing temp Label
(mass %) (g) (mass %) (g) (g) (g) (mass %) time (h) (.degree. C.) A
12 500 10 27.4 34.8 437.2 0.5 11.5 28 B 12 500 10 27.4 34.8 437.2
0.5 12.5 33 C 12 1,500 10 84.0 104.4 1311.6 0.5 15 28 D 11 1,000 4
46.3 63.7 890 0.2 10 31
[0062] In a representative spin using the equipment described
hereinabove, with a 150 .mu.m diameter spinneret and a pump flow
rate was 0.10 cm.sup.3min..sup.-1, the residence time in the ethyl
acetate bath was 77 s. The heating tube temperature was 85.degree.
C., and 18.8 g of fiber having a diameter of 86.+-.2 .mu.m were
collected over 150 min. The speed of the first godet was 3.0 rpm
(.about.1.56 mmin.sup.-1). The speed of rotation of the second
godet was varied between 1.2 and 2.7 times faster than the first
godet, in steps (3.6; 4.5; 5.4; 6.3; 7.2; and 8.1 rpm, as
examples). Fiber samples were collected for several minutes at each
speed for further measurements. When the stretch ratio was higher
than 3.0 for these fiber processing conditions, it was found that
continuous fiber spinning became difficult, suggesting that the
limit of the stretch ratio for these conditions is .ltoreq.3
(2.sup.nd godet speed of rotation.ltoreq.9 rpm). TABLE 2 shows the
variation of fiber properties with increasing amounts of stretch
between the godets.
TABLE-US-00002 TABLE 2 Peak Speed ratio Diameter Conductivity
Stress Modulus Extn. at godet 2:godet 1 (.mu.m) Denier* (S
cm.sup.-1) (MPa) (GPa) break (%) 1.2 93 .+-. 2 103 335 .+-. 25 62
.+-. 5 0.6 .+-. 0.1 84 .+-. 8 1.5 84 .+-. 2 79 445 .+-. 40 77 .+-.
5 1.1 .+-. 0.1 60 .+-. 4 1.8 78 .+-. 2 68 525 .+-. 4 70 .+-. 8 1.4
.+-. 0.1 42 .+-. 10 2.1 70 .+-. 2 55 630 .+-. 65 79 .+-. 2 2.1 .+-.
0.1 29 .+-. 10 2.4 66 .+-. 2 48 750 .+-. 80 97 .+-. 5 2.6 .+-. 0.2
14 .+-. 4 2.7 62 .+-. 2 43 810 .+-. 100 111 .+-. 3 2.9 .+-. 0.4 12
.+-. 4 *Denier is defined as the number of grams per 9000 m of
fiber.
[0063] D. Dopant Exchange of the Polyaniline Fibers
[0064] Since the performance of conducting-polymer-based devices is
known to be dependent on the properties of dopant anions, for
certain applications it may be desirable to replace the dopants
(AMPSA and DCAA, as examples), present in the polyaniline fibers as
a result of the acid-spinning process, with other dopants. Dopants
present in polyaniline fibers can be partially or totally replaced
with selected dopants during: (a) the spinning process; (b)
post-spinning dopant manipulation; and (c) fiber conversion to the
insulating EB form (dedoped) as part of the spinning process,
followed by redoping with a selected acid. The three approaches
have been fount to generate the same electrical and mechanical
properties in the doped form of the fibers. The removal of DCAA
from the as-spun fiber is advantageous since residual DCAA has been
found to slowly degrade the mechanical properties of polyaniline
fiber, and because it is a hazardous compound.
[0065] A dedoping procedure for removing dopants (AMPSA and DCAA,
as examples) from the as-spun fibers which results in fibers having
low room-temperature conductivity is now described. Essentially all
of the dopants can be removed from as-spun fiber without
substantially changing the mechanical properties of the fiber,
which converts the fibers from their conductive emeraldine salt
oxidation state into their neutral emeraldine base oxidation state.
Polyaniline fibers were dedoped by placing them in contact with a
0.1 M aqueous solution of NH.sub.4OH as either part of the spinning
process or by a subsequent post-treatment process for between 15
min. and 3 h. The high volatility of ammonium hydroxide compared
with sodium hydroxide permits its complete removal from the fiber.
By contrast, it was found that use of sodium hydroxide results in
the incorporation of sodium ions into the resulting dedoped
fiber.
[0066] The dedoped polyaniline fibers could then be rendered
conductive by immersing the fibers in an acidic solution having
pH.ltoreq.3. In a typical procedure, the dedoped polyaniline fiber
was redoped by immersing the fiber in a 1.0 M solution of the
desired acid for 24 h. The redoped fibers were then dried under
ambient conditions for at least 48 h before being incorporated into
a device.
[0067] E. Measurement of the Conductivity of the Polyaniline
Fibers
[0068] Conductivity as a function of temperature, conductivity and
temperatures as a function of applied constant current, and
conductivity and temperature as a function of applied constant
voltage were studied for doped polyaniline fiber using
chromel-constantan differential thermocouples (chromel contains 90%
Ni and 10% Chromium; and constantan contains 45% nickel and 55%
copper).
[0069] II. Characteristics of Polyaniline Fibers:
[0070] A. Temperature-Dependent Conductivity of Polyaniline
Fibers:
[0071] FIG. 1 is a graph of the DC conductivity for a polyaniline
fiber (PANI.AMPSA.sub.0.2.
DCAA.sub.0.27.(H.sub.3PO.sub.4).sub.0.35, where each of these
numbers corresponds to the number of acid molecules per nitrogen
atom on the polyaniline backbone) a function of temperature, while
FIG. 2 shows the change of temperature of a 12 mm long, 95 .mu.m
diameter polyaniline fiber resulting from resistive heating as a
function of applied voltage, where the base temperature is
22.9.degree. C. Thermogravimetric analysis of this polyaniline
fiber indicates that the onset of thermal decomposition occurs when
the temperature exceeds 180.degree. C.
[0072] B. Humidity Dependent Conductivity of Polyaniline
Fibers:
[0073] The electrical conductivity of doped PANI changes with the
humidity of the environment and other gas vapors. The humidity
dependent conductivity change is not due to a chemical reaction,
and is not a result of the degradation of the conducting polymers,
but due to a change of the Fermi level of the polymer when an
electron-donating or electron-withdrawing gas is absorbed to its
surface. Therefore, such changes have a high degree of
reversibility. FIG. 3 shows the resistance change of a polyaniline
fiber (length: 136.0 mm, diameter: 84 .mu.m) as a function of
relative humidity at room temperature (26.5.degree.
C..+-.0.5.degree. C.). Resistance measurements in FIG. 3 are taken
when the change in resistance at a particular relative humidity is
less than 1% (approximately at equilibrium).
[0074] If there is no dimensional change, the resistance of
polyaniline fibers changes with both temperature and humidity. To
decouple the data acquired from a sensor fabric, the conducting
polymers are separated into two groups. One group is kept in a
humidity controlled environment, so that the resistance changes
only with temperature. The other group is exposed to ambient air,
and the resistance changes both with temperature and humidity. By
using a differential amplifier (either digital or analog), or a
lookup table method, the temperature and humidity signals are
decoupled and acquired.
[0075] C. Behavior of Polyaniline Fibers Under an Overloading
Electrical Stimulus:
[0076] As can be seen from FIG. 2 hereof, the temperature of
conducting polymer fibers increases when an electrical stimulus,
either an applied voltage or current, is applied to the fiber as a
result of resistive heating. Unlike most conductive wires, which
melt when the applied current or voltage is excessive, the
temperature at which polyaniline fibers lose their conductivity can
be much lower than the thermal decomposition temperature of the
fiber. FIG. 4a is a graph of the resistance as a function of time
for a 4.5 V voltage applied to a polyaniline fiber
(PANI.AMPSA.sub.0.2. DCAA.sub.0.27.(H.sub.3PO.sub.4).sub.0.35,
where each of these numbers corresponds to the number of acid
molecules per nitrogen atom on the polyaniline backbone) having a
length of 12.0 mm and a diameter 95 .mu.m, while FIG. 4b is a graph
of the temperature change as a function of time for this fiber. The
base temperature of the fiber was 22.9.degree. C. The temperature
at which the conductivity of the fiber is destroyed is seen to be
about 47.9.degree. C., which is much lower than its thermal
decomposition temperature (180.degree. C.) for this fiber. As
stated hereinabove, typically, the decomposition temperature of
conducting polyaniline fibers depends on the dopant employed, and
ranges between about 120 and 250.degree. C. For example, HCl-doped
polyaniline fibers decompose at around 120.degree. C., those doped
with phosphoric acid decompose at about 250.degree. C., and those
doped with sulfonic acids generally decompose at approximately
200.degree. C. The fiber resistance at 47.9.degree. C. should be
29.5.OMEGA..
[0077] D. Conductivity of Polyaniline Fibers as a Function of
Linear Extension:
[0078] FIG. 5 is a graph of the change of resistance of a
polyaniline fiber as a function of applied force for a fiber having
a diameter of 118 .mu.m and a length of 60 mm; the temperature was
24.2.degree. C., and the relative humidity was 20% RH. As shown in
FIG. 6a, the 40 denier polyaniline monofilament (dark fibers) are
knitted into a fabric with Nylon yarn (light fibers).
[0079] FIG. 7a shows the percent change of resistance of the
polyaniline monofilament knitted into the fabric shown in FIG. 6
hereof as a function of the percent extension of the fabric, while
FIG. 7b shows the percent change of resistance thereof as a
function of applied force (N). Hence, the conducting polymer fiber
in the knitted fabric can monitor both the amount of applied load
(stress) as well as geometric displacement (strain) of the
fabric.
[0080] Having generally described the invention, the following
EXAMPLES provide further detail.
Example 1
Location of Blood Emission from a Wound and Resistive Heating
[0081] In a grid of conductive fibers shown in FIG. 8a, where a
first plurality of substantially parallel fibers (shown as vertical
fibers in FIG. 8a) is separated from a second plurality of
substantially parallel fibers oriented approximately
perpendicularly (shown as horizontal fibers in FIG. 8a) to the
first set of fibers using an insulator fabric layer 102, if a
conducting liquid, 100, say, a drop of blood is absorbed by
insulating layer 102 near the intersection of conducting polymer
fibers; for example, near the intersection of fiber, 104, and
fiber, 106, respectively, the electrical insulation between the two
fibers will change significantly. By measuring electrical signals
resulting from the change in the conductivity of the fibers, the
position of the electrolyte can be determined.
[0082] Voltage from power source, 108, is connected to the two sets
of parallel fibers by means of switch SW.sub.x, 110, and SW.sub.y,
112, respectively. The voltage on the fibers is measured using volt
measuring device, 120, through switch circuit, 118, using a
scanning method; one fiber at a time. If Pulse Width Modulation
(PWM) signal, 122, is introduced onto the first set of parallel
fibers (See, FIG. 8b), when the voltage on the second set of
parallel wires is measured, as a result of the electrolyte present
at the intersection of fibers 104 and 106, a voltage pulse will be
observed. Such a signal indicates that there is electrolyte present
on fiber 106. When a similar PWM signal is applied to the second
set of parallel fibers, a voltage pulse will appear on the first
set of fibers on fiber 104, which means that electrolyte is present
on that fiber. Combining these two pieces of information, the
position of the electrolyte is obtained. The PWM signals can also
be used to control the temperature of the dual purpose fabric
through resistive heating. The sampling rate of the fabric fibers
determines the minimum duty cycle and the highest repeat frequency
of the PWM, the highest achievable duty cycle being 50%, since the
two sets of fibers cannot be stimulated simultaneously. Signals in
the fabric are controlled and acquired by a control module, the
block diagram of which is depicted in FIG. 8c. In the control
module, power source 108, multichannel voltage measuring device,
114, consisting of switch circuit, 118, voltage measuring device,
120, and switches SW.sub.x (110) and SW.sub.y (112) are controlled
by microprocessor-based central controller, 126.
Example 2
Breathing Sensor Fabric
[0083] The woven fabric shown in FIGS. 6a and 6b can also be used
to sense breathing rate, since breathing is a continuously
repeating movement, and the frequency and amplitude of resistance
change caused by breathing are significantly different from that
affected by the temperature and humidity. Therefore, decoupling can
readily be achieved.
Example 3
Shape Sensor Fabrics
[0084] As stated hereinabove, resistance of the polyaniline fibers
varies with the application of a force to the fiber which gives
rise to a dimensional change along its length (See, FIGS. 7a and 7b
hereof). Based on this characteristic, shape/stress sensors can be
made using polyaniline fibers. FIGS. 9a to 9c show three types of
shape sensors. In FIG. 9a, a first set of parallel conducting
polymer fibers, fiber, 208, as an example are attached to frame,
206, and a second set of parallel fibers, fiber, 210, as an
example, the two sets of parallel fibers being electrically
isolated by isolation layer, 212. For either the first set or the
second set of parallel fibers, two pieces of conducting polymer
fiber, one exposed to air, 215, and the other coated, 220, are
immobilized on frame 206 and electrically connected to fiber 210 in
the second set of fibers, as an example, for temperature and
humidity sensing. As shown, fiber 215 is connected to fiber 210 at
point 214, and fiber 220 is connected to fiber 215 at point 216.
Resistance of the 3 polyaniline fibers is measured by applying a
constant current from current source, 200, through switch circuit,
204, and the voltages measured one at a time by voltage measuring
device, 202, through switch circuit 204 using a scanning method at
points 214, 216 and 218. The voltage at point 216 only changes with
the temperature, while that between 214 and 216 changes with
temperature and humidity. The voltage between 218 and 216 is
affected by the temperature, humidity and the stress on fiber 210.
Accordingly, by using differential amplifiers (not shown in the
figure) or differential or lookup table algorithms (employed by a
microprocessor), the humidity, temperature and shape change on
fiber 210 can be obtained. The change of shape of the wires within
the frame can be monitored by scanning the fiber matrix.
[0085] FIG. 9b shows another type of sensor. Here the first set of
parallel fibers and the second set of parallel fibers are composed
of single fibers. One end of each fiber is grounded, while the
other end is connected to a constant current source, 232.
Resistance of the sensing pieces is acquired by dividing the
voltage difference by the current i, and the voltages are measured
by voltmeter 230 through switch 234 at electrical contacts 242,
244, 246, and 248 using a scanning method. Resistances of the
fibers fixed on the frame, for example 252 and 254, are used to
decouple the effects of temperature and humidity by differential
amplifiers (not shown in the figure) or microprocessors (using
differential or lookup table algorithms). Compared to that shown in
FIG. 9a, the sensor shown in FIG. 9b has the current source
connected directly to one end of the fibers and, therefore, the
switch circuit is simplified. However, as shown in FIG. 9b, any
broken fiber piece will cause the failure of the entire device.
Thus, the reliability of this sensor is not as good as that for the
device illustrated in FIG. 9a.
[0086] For the sensors shown in FIG. 9a and FIG. 9b, the force can
only be applied in one direction. In FIG. 9c, the 3-D shape sensor,
on which the force can be applied in three dimensions is
schematically shown. In this sensor, conducting polymer fibers, for
example 270 can be inserted on an elastic body 272 to form a 3-D
shape sensor, which is used to sense the shape change in 3-D space.
In FIG. 9c, the second set of parallel conductive coating lines,
for example 268, and the first set of parallel coating lines, for
example, 274, are connected with a switch circuit, 264, and the
resistances of the conducting polymer fibers are measured using a
scanning method by applying constant current from a current source,
260, and measuring the voltage by using voltmeter, 262. Since the
conducting polymer fibers are sealed in the elastic body, humidity
change will have little effect on the resistance of the fibers.
Effects of temperature can be compensated in data processing, and
an extra temperature sensor is needed. The scanning process is
controlled by a control module (FIG. 9d), which is also used for
acquiring the signals, and data processing. In the control module,
a microprocessor-based central computer, 286, is used to control
the multi-channel, 290, that consists of a switch circuit, 282, and
a voltage meter, 284.
Example 4
Touch Sensor
[0087] FIG. 10a is a schematic representation of a polyaniline
touch sensor, 314, which includes a polyaniline fiber, 308, and a
metal wire coated with varnish, 304. Varnish, 310, is used to
attach the metal wire to the polyaniline fiber. The top of the
metal wire is placed in electrical connection with the polyaniline
fiber using silver conducting paint, 312. When the sensor is
touched it will bend, 314, and the polyaniline fiber is extended.
By monitoring the resistance change schematically shown in FIG.
10b, for example, between 318 and 320, knowledge that the device
has been touched or has touched something is obtained. This type of
sensor has been made with a diameter of between 50 and 200 .mu.m,
and therefore, by using a spectrum division approach, the touch
sensor can be used as a probe to measure the geometry of
sub-millimeter structures in a number of manufacturing areas,
including optical fibers, automotive (fuel injectors), and
electronics (microwave attenuation standards), in which the optical
methods have unsolved problems with diffraction.
[0088] By adding two pieces of fiber, one is coated only for
temperature sensing, 326, and the other one is exposed to air for
temperature and humidity sensing, 324, on a fixed frame, the touch
sensor can also be used for temperature and humidity sensing and
therefore, by using differential amplifiers (not shown in the
figure) or differential of lookup table algorithms (employed by a
microprocessor), it can be used in an environment in that the
temperature and humidity change. Resistance of the sensing pieces
is measured by applying a constant current from a constant current
source, 322, and then voltages on the coated fiber piece on frame,
326, the exposed fiber piece on frame, 324, and the touch sensor
piece, 314, are measured by the voltage meter 300 through switch
circuit 302.
Example 5
Multifunction Conducting Polymer Devices
[0089] FIG. 11 shows a schematic representation of a conducting
polymer heating element, 400, capable of generating heat when
current is passed therethrough, the resistivity of the heating
element varying with temperature such that from the measurement of
the resistivity of the element and adjustment of the applied
current, a chosen temperature can be maintained. Also in FIG. 11, a
single controller, 402, is shown for providing both the temperature
sensing and the voltage generation functions. Differential
algorithms or lookup table methods can be used by the controller
for temperature sensing.
[0090] Different from other resistive heating devices that use a
separate temperature sensor (e.g. a thermocouple or a thermistor)
for temperature feedback, the present multifunctional devices
monitor the temperature of the heating element by measuring its
resistance change. In addition, as illustrated in FIG. 11, from
room temperature to about 100.degree. C., the conductivity change
of the polyaniline fibers is significant (>30%). Accordingly, a
simple resistance measuring device other than high precision
devices, which are needed to measure the resistance change of some
metal wires such as copper or aluminum due to the tiny conductivity
change in this temperature range, can be used for monitoring the
temperature. The multifunctional feature of the polyaniline
fibers--as a resistive temperature device, and a wire that can
conduct a large current enables the compact and economical
resistive heating fabric. Other multifunction devices can also be
envisioned using conducting polymer fibers and fabrics. As an
example, humidity control in a chamber can be achieved by supplying
current to a conducting polymer fiber onto which water is absorbed,
where the current is controlled by a feedback system which receives
resistance measurements from the fiber which are responsive to the
relative humidity to which the fiber is exposed.
[0091] The foregoing description of the invention has been
presented for purposes of illustration and description and is not
intended to be exhaustive or to limit the invention to the precise
form disclosed, and obviously many modifications and variations are
possible in light of the above teaching. The embodiments were
chosen and described in order to best explain the principles of the
invention and its practical application to thereby enable others
skilled in the art to best utilize the invention in various
embodiments and with various modifications as are suited to the
particular use contemplated. It is intended that the scope of the
invention be defined by the claims appended hereto.
* * * * *