U.S. patent application number 17/292031 was filed with the patent office on 2021-12-23 for mxene-based sensor devices.
The applicant listed for this patent is Deakin University, Drexel University. Invention is credited to Genevieve DION, Yury GOGOTSI, Shayan SEYEDIN, Amy L. STOLTZFUS, Simge UZUN.
Application Number | 20210396607 17/292031 |
Document ID | / |
Family ID | 1000005870367 |
Filed Date | 2021-12-23 |
United States Patent
Application |
20210396607 |
Kind Code |
A1 |
UZUN; Simge ; et
al. |
December 23, 2021 |
MXENE-BASED SENSOR DEVICES
Abstract
Provided are sensors comprising one or both of MXene-coated
fibers and MXene-coated yarns. The MXene-coated yarns can be
utilized for various types of smart textile applications where
conductivity is required. These include but are not limited to
sensors (e.g. pressure, strain, moisture, and temperature),
supercapacitors, triboelectric generators, antennas, and
electromagnetic interference (EMI) shielding textiles.
Inventors: |
UZUN; Simge; (Philadelphia,
PA) ; GOGOTSI; Yury; (Warminster, PA) ; DION;
Genevieve; (Philadelphia, PA) ; STOLTZFUS; Amy
L.; (Philadelphia, PA) ; SEYEDIN; Shayan;
(Belmont, AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Drexel University
Deakin University |
Philadelphia
Geelong |
PA |
US
AU |
|
|
Family ID: |
1000005870367 |
Appl. No.: |
17/292031 |
Filed: |
November 8, 2019 |
PCT Filed: |
November 8, 2019 |
PCT NO: |
PCT/US2019/060549 |
371 Date: |
May 7, 2021 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62767092 |
Nov 14, 2018 |
|
|
|
62757321 |
Nov 8, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01L 2019/0053 20130101;
D02G 3/441 20130101; D10B 2401/18 20130101; G01L 1/2287 20130101;
G01L 19/147 20130101; D10B 2401/16 20130101 |
International
Class: |
G01L 1/22 20060101
G01L001/22; D02G 3/44 20060101 D02G003/44 |
Claims
1. A pressure sensor, comprising: a first electrode; a second
electrode; and a dielectric material disposed so as to place the
first electrode into electrical isolation from the second
electrode, at least one of the first electrode and the second
electrode comprising (a) a substrate fiber, the substrate fiber
defining an outer surface coated with a first plurality of MXene
particulates, (b) a yarn comprising a plurality of coating fibers,
each coating fiber comprising a substrate fiber defining an outer
surface coated with a first plurality of MXene particulates, (c) a
yarn comprising a plurality of coating fibers, each coating fiber
comprising a substrate fiber defining an outer surface coated with
a first plurality of MXene particulates and the yarn defining an
outer surface coated with a second plurality of MXene particulates,
or (d) a yarn comprising a plurality of fibers, the yarn defining
an outer surface coated with a second plurality of MXene
particulates.
2. The pressure sensor of claim 1, wherein at least one of the
first electrode and the second electrode is characterized as being
a woven fabric, a knitted fabric, or a nonwoven fabric.
3. The pressure sensor of claim 1, wherein a substrate fiber
comprises a synthetic material or a natural material.
4. The pressure sensor of claim 4, wherein the first plurality of
MXene particulates has an average particle size in the range of
from about 100 to about 1000 nm.
5. The pressure sensor of claim 1, wherein the first plurality of
MXene particulates comprises two different MXene materials.
6. The pressure sensor of claim 1, wherein the first plurality of
MXene particulates defines a unimodal particle size
distribution.
7. The pressure sensor of claim 1, wherein the first plurality of
MXene particulates defines a multimodal particle size
distribution.
8. The pressure sensor of claim 1, wherein the first plurality of
MXene particulates are attached to the substrate fiber by
electrostatic interaction.
9. The pressure sensor yarn of claim 1, wherein the second
plurality of MXene particulates has an average particle size in the
range of from about 500 to about 15,000 nm.
10. The pressure sensor of claim 1, wherein the second plurality of
MXene particulates comprises two different MXene materials.
11. The pressure sensor of claim 1, wherein the second plurality of
MXene particulates defines a unimodal particle size
distribution.
12. The pressure sensor of claim 1, wherein the second plurality of
MXene particulates are attached to the outer surface of the yarn by
electrostatic interaction.
13. The pressure sensor of claim 1, wherein the yarn is
characterized as having a MXene loading of from about 0.1 to about
2.0 mg/cm.
14. The pressure sensor of claim 1, wherein the yarn is
characterized as having a MXene mass loading of from about 10 to
about 75 wt %.
15. The pressure sensor of claim 1, wherein the yarn is
characterized as having a conductivity of from about 30 to about
150 S/cm.
16. The pressure sensor of claim 1, wherein the pressure sensor is
characterized as having a gauge factor of from about 0.1 to about
10.
17. A method, comprising operating a pressure sensor according to
claim 1.
18. A strain sensor, comprising: a sensor region, the sensor region
comprising (a) a substrate fiber, the substrate fiber defining an
outer surface coated with a first plurality of MXene particulates,
(b) a yarn comprising a plurality of coating fibers, each coating
fiber comprising a substrate fiber defining an outer surface coated
with a first plurality of MXene particulates, (c) a yarn comprising
a plurality of coating fibers, each coating fiber comprising a
substrate fiber defining an outer surface coated with a first
plurality of MXene particulates and the yarn defining an outer
surface coated with a second plurality of MXene particulates, or
(d) a yarn comprising a plurality of fibers, the yarn defining an
outer surface coated with a second plurality of MXene particulates;
and a charge collector configured to monitor a signal of the sensor
region related to a strain experienced by the panel.
19. The strain sensor according to claim 18, the sensor region
being characterized as being a knitted fabric, a woven fabric, or a
nonwoven fabric.
20. A method, comprising operating a pressure sensor according to
claim 1.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present disclosure claims priority to and the benefit of
U.S. patent application No. 62/757,321, "MXene Coated Yarns And
Textiles For Functional Fabric Devices" (filed Nov. 8, 2018) and
U.S. patent application No. 62/767,092, "MXene Coated Yarns And
Textiles For Functional Fabric Devices" (filed Nov. 14, 2018), the
entireties of which applications are incorporated herein by
reference for any and all purposes.
TECHNICAL FIELD
[0002] The present disclosure is directed to fabrics and clothing
containing functional textile devices.
BACKGROUND
[0003] The recent surge of interest in textile-based electronics
has directed research efforts towards designing multifunctional
fibers and yarns. Electrically conducting yarns are quintessential
for wearable applications because they can be engineered to perform
specific functions in a wide array of technologies such as energy
storage, sensing, actuation, and communication.
[0004] However, many challenges remain unaddressed regarding
manufacturability of functional fibers and their integration in
textiles. Current wearables utilize conventional batteries, which
are bulky, uncomfortable, and can impose design limitations to the
final product. Therefore, the development of flexible,
electrochemically and electromechanically active yarns, which can
be engineered and knitted into full fabrics provide new and
practical insights for the scalable production of textile-based
devices.
SUMMARY
[0005] In meeting the long-felt needs described above, the present
disclosure provides a pressure sensor, comprising: a first
electrode; a second electrode; and a dielectric material disposed
so as to place the first electrode into electrical isolation from
the second electrode, at least one of the first electrode and the
second electrode comprising (a) a substrate fiber, the substrate
fiber defining an outer surface coated with a first plurality of
MXene particulates, (b) a yarn comprising a plurality of coating
fibers, each coating fiber comprising a substrate fiber defining an
outer surface coated with a first plurality of MXene particulates,
(c) a yarn comprising a plurality of coating fibers, each coating
fiber comprising a substrate fiber defining an outer surface coated
with a first plurality of MXene particulates and the yarn defining
an outer surface coated with a second plurality of MXene
particulates, or (d) a yarn comprising a plurality of fibers, the
yarn defining an outer surface coated with a second plurality of
MXene particulates.
[0006] Also provided are methods, comprising operating a pressure
sensor according to the present disclosure.
[0007] Further provided are strain sensors, comprising: a sensor
region, the sensor region comprising (a) a substrate fiber, the
substrate fiber defining an outer surface coated with a first
plurality of MXene particulates, (b) a yarn comprising a plurality
of coating fibers, each coating fiber comprising a substrate fiber
defining an outer surface coated with a first plurality of MXene
particulates, (c) a yarn comprising a plurality of coating fibers,
each coating fiber comprising a substrate fiber defining an outer
surface coated with a first plurality of MXene particulates and the
yarn defining an outer surface coated with a second plurality of
MXene particulates; and or (d) a yarn comprising a plurality of
fibers, the yarn defining an outer surface coated with a second
plurality of MXene particulates, and a current collector configured
to monitor a signal of the sensor region related to a strain
experienced by the panel.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The present application is further understood when read in
conjunction with the appended drawings. For the purpose of
illustrating the subject matter, there are shown in the drawings
exemplary embodiments of the subject matter; however, the presently
disclosed subject matter is not limited to the specific methods,
devices, and systems disclosed. In addition, the drawings are not
necessarily drawn to scale.
[0009] FIG. 1. Seamlessly knitted MXene-coated cellulose-based
yarns. Concept illustration of a garment integrated with energy
storage and harvesting device with a capacitive pressure sensor.
Insets show actual device prototypes comprising of a) Knitted
energy storing fabric with alternating MXene-coated cotton yarn
(black) and a non-conductive commercial viscose yarn (green). b)
Knitted energy harvesting fabric with alternating MXene-coated
linen yarn (black) and a commercial Teflon yarn (brown) can be
placed strategically to harvest energy from body movements. c)
Capacitive pressure sensor device knitted with MXene-coated bamboo
yarn, where the device can sense different applied pressures
ranging from low to high.
[0010] FIG. 2. Characterization of Ti.sub.3C.sub.2 MXene
dispersions. a) Digital photograph of .about.100 mL of MXene
dispersion (.about.20-25 mg/mL) in a petri dish with a schematic of
the atomic structure of Ti.sub.3C.sub.2 MXene flake. b) Zeta
potential (graph) at pH 6.8 and transmission electron microscopy
(TEM) image (inset) of probe sonicated (S--Ti.sub.3C.sub.2) MXene
flakes. c) Flake-size distribution of as-synthesized
(L-Ti.sub.3C.sub.2) and S--Ti.sub.3C.sub.2 MXene dispersions. The
size is represented as hydrodynamic diameter (d, nm) in nanometers.
Insets: Scanning electron microscopy (SEM) images of
S--Ti.sub.3C.sub.2 (Top) and L-Ti.sub.3C.sub.2 (Bottom) MXene
flakes. Two-step coating process of highly conductive MXene-coated
cotton yarns. First coating step (fiber coating) requires using
S--Ti.sub.3C.sub.2 MXene flakes, which enables MXene penetration
into the fiber level. Second coating step (yarn coating) uses
L-Ti.sub.3C.sub.2 MXene flakes to cover the yarn surface to provide
high conductivity. The schematic illustration of the cross-section
of cotton yarn d) pristine, e) coated with S--Ti.sub.3C.sub.2 MXene
flakes, f) coated with S--Ti.sub.3C.sub.2 and L-Ti.sub.3C.sub.2
MXene flakes. Cross-section SEM images of g) pristine cotton
fibers, h) cotton fibers coated with S--Ti.sub.3C.sub.2 MXene
flakes, i) cotton yarn after being coated with S--Ti.sub.3C.sub.2
and L-Ti.sub.3C.sub.2 MXene flakes. SEM images of the cotton yarn
surface j) pristine, k) coated with S--Ti.sub.3C.sub.2 MXene
flakes, and l) coated with S--Ti.sub.3C.sub.2 and L-Ti.sub.3C.sub.2
MXene flakes.
[0011] FIG. 3. Different stitch patterns commonly used in knitted
fabrics. a) Single jersey. b) Half gauge. c) Interlock. d) attempt
to knit MXene-coated cotton yarn (black) in single jersey pattern.
e) MXene-coated cotton yarn knitted with half gauge pattern
resulted in a porous fabric. f) MXene-coated cotton yarn knitted
with interlock pattern resulted in a dense fabric.
[0012] FIG. 4. Washing durability performance of MXene-coated
cotton yarns (.about.2 mg/cm MXene loading) under various washing
temperatures and times. a) The change in the MXene loading and the
linear resistance as a function of washing temperature ranging from
30.degree. C. to 80.degree. C. Ti.sub.2p XPS spectra of b) unwashed
MXene-coated cotton yarn and c) washed MXene-coated cotton yarn
after 3 min of sputtering. The yarns were washed for 20 washing
cycles at 30.degree. C. and 5 washing cycles at temperatures
ranging from 40.degree. C. to 80.degree. C.
[0013] FIG. 5. Electrochemical performance of MXene-coated cotton
yarns with 78 wt. % (2.5 mg/cm) MXene loading using a
three-electrode cell in 1 M H.sub.2SO.sub.4. a) Cyclic voltammetry
(CV) curves (5 mV/s) at various operation potentials. b) CV curves
of MXene-coated yarns at various scan rates. c) Galvanostatic
charge-discharge (GCD) curves at various current densities. d) Rate
capability of length and linear density capacitance of MXene-coated
cotton yarns. e) Normalized Nyquist plot based on the length of the
yarn, f) Cyclic stability of the MXene-coated cotton yarn during
10,000 cycles at a current density of 30 mA/cm.
[0014] FIG. 6. Evaluation of sensing performance of the capacitive
knitted pressure sensor device. a) Schematic representation of the
capacitive pressure sensor (active area--16 mm.times.26 mm)
assembled by using two knitted fabric electrodes and a dielectric
layer. b) Electromechanical behavior of the knitted sensor. The
applied strain is incrementally increased from 2.8% to 19.7%. Each
cyclic deformation is repeated 20 times. c) Capacitance as a
function of time at different compression strains ranging from 2.8%
to 19.7%. The hold time is 10 seconds. d) Relative capacitance
changes of the sensor at various strains. Gauge factor (GF) is
derived from the linear fit. e) Cyclic stability of the sensor
based on relative capacitance change at 14.1% strain for 2,000
cycles. f) Top: Digital photo of the knitted pressure sensor button
(active area--16 mm.times.5 mm). Bottom: Capacitance output of the
sensor when a gentle, moderate, or hard pressure is applied to the
device by a finger.
[0015] FIG. 7. a) X-ray diffraction (XRD) patterns of pristine
cotton yarn, Ti.sub.3C.sub.2 MXene-coated cotton yarn,
Ti.sub.3C.sub.2 MXene film (made with L-Ti.sub.3C.sub.2), and
Ti.sub.3AlC.sub.2 MAX powder. Asterisk (*) indicates a second layer
of intercalated water within the structure. The prefixes "M" and
"C" in the composite spectra indicate MXene and cotton peaks,
respectively. b) TEM image of L-Ti.sub.3C.sub.2 MXene flake. AFM
images and the line profile of the c) S--Ti.sub.3C.sub.2 MXene
flake and d) L-Ti.sub.3C.sub.2 MXene flake.
[0016] FIG. 8. Cross-section SEM images of cotton (top), bamboo
(middle), and linen (bottom) yarns and fibers before and after
Ti.sub.3C.sub.2 coating.
[0017] FIG. 9. a) Resistance and conductivity change of the
MXene-coated cotton, bamboo, and linen yarns as a function of
length. b) Typical tensile stress-strain curves of pristine and
MXene-coated cellulose-based yarns. c) SEM image of knotted
MXene-coated cotton yarn with 78 wt. % active material loading.
[0018] FIG. 10. SEM images of a) unwashed and b) washed
MXene-coated cotton yarn surface. c) XPS spectrum of the washed
MXene-coated cotton yarn without sputtering. The washed samples
went through 20 washing cycles at 30.degree. C. and 5 washing
cycles ranging from 40.degree. C. to 80.degree. C.
[0019] FIG. 11. SEM images of the a) pristine cotton yarn b) after
10,000 cycles in 1 M H.sub.2SO.sub.4.
[0020] FIG. 12. Electrochemical performance of a symmetric MXene
cotton yarn supercapacitor device using a cotton yarn with 2.2
mg/cm of MXene loading in 1 M PVA--H.sub.2SO.sub.4 gel electrolyte.
a) CV curves at different scan rates, b) GCD curves at different
current densities, c) Specific length and linear density
capacitance of the device calculated from CV curves, d)
Electrochemical impedance spectroscopy of yarn supercapacitor
device, e) Capacitance retention and Coulombic efficiency versus
cycle number at a current density of 5 mA/cm, f) Capacitance
retention of the device under different bending angles. Inset shows
capacitance retention after bending from 0.degree. to
90.degree..
[0021] FIG. 13 provides exemplary showing that capacitance (C)
increased with applied stress (FIG. 13a). Moreover, 20% and 50%
increases in the capacitance response were observed when 5 g and 20
g weights were placed on the textile device, respectively (FIG.
13b).
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0022] The present disclosure may be understood more readily by
reference to the following detailed description taken in connection
with the accompanying figures and examples, which form a part of
this disclosure. It is to be understood that this invention is not
limited to the specific devices, methods, applications, conditions
or parameters described and/or shown herein, and that the
terminology used herein is for the purpose of describing particular
embodiments by way of example only and is not intended to be
limiting of the claimed invention.
[0023] Also, as used in the specification including the appended
claims, the singular forms "a," "an," and "the" include the plural,
and reference to a particular numerical value includes at least
that particular value, unless the context clearly dictates
otherwise. The term "plurality", as used herein, means more than
one. When a range of values is expressed, another embodiment
includes from the one particular value and/or to the other
particular value. Similarly, when values are expressed as
approximations, by use of the antecedent "about," it will be
understood that the particular value forms another embodiment. All
ranges are inclusive and combinable, and it should be understood
that steps may be performed in any order.
[0024] It is to be appreciated that certain features of the
invention which are, for clarity, described herein in the context
of separate embodiments, may also be provided in combination in a
single embodiment. Conversely, various features of the invention
that are, for brevity, described in the context of a single
embodiment, may also be provided separately or in any
subcombination. All documents cited herein are incorporated herein
in their entireties for any and all purposes.
[0025] Further, reference to values stated in ranges include each
and every value within that range. In addition, the term
"comprising" should be understood as having its standard,
open-ended meaning, but also as encompassing "consisting" as well.
For example, a device that comprises Part A and Part B may include
parts in addition to Part A and Part B, but may also be formed only
from Part A and Part B.
[0026] The present invention relates to MXene coated conductive
yarns and knitted fabrics (as well as woven and non-woven fabrics)
and the use of such yarns to create functional textile devices
seamlessly integrated into fabric products including but not
limited to garments. The objective of the system described herein
is to realize a low-cost, yarn coating system to create a variety
of textile-based applications.
[0027] The invention includes the development of a facile and
scalable dip-coating approach for producing highly conductive and
durable MXene coated yarns. Concentration and flake size
distribution of MXene dispersions are tailored to ensure
penetration of MXene flakes at the fiber and/or yarn level. The
coating process can be easily tailored to match specific
conductivity and/or electrochemistry requirements for the desired
final application.
[0028] Fibers are the fundamental units of yarns, and the yarns are
the building blocks of the textiles. The commercial yarns used for
dipping process include but not limited to natural, synthetic
fibers, and their blends, such as cotton, bamboo, linen, modal,
regenerated cellulose, nylon, polyester, viscose, and more.
[0029] The MXene-coated yarns can be utilized for various types of
smart textile applications where conductivity is required. These
include but are not limited to sensors (e.g. pressure, strain,
moisture, and temperature), supercapacitors, triboelectric
generators, antennas, and electromagnetic interference (EMI)
shielding textiles. The coating process can be easily tailored
based on the specific requirements of the target application.
[0030] An exemplary yarn MXene dip coating process is as
follows.
[0031] Coating with small flakes: MXene dispersion with small
flakes (.about.250-400 nm) is used to dip-coat individual fibers.
This type of coating retains the original property of the yarn and
gives sufficient conductivity for variety of applications such as
pressure and strain sensor. In case of a pressure sensor, when
pressure is applied to the yarn, the small MXene flakes between
individual fibers result in higher sensitivity to the changes in
applied pressure due to higher possible number of contact points
between the flakes.
[0032] Coating with large flakes: MXene dispersion with large
flakes (e.g. 9.4%--6789 nm, 85%--940 nm, 5.6%--200.1 nm) is used to
dip-coat yarn surface. When only MXene dispersions with large
flakes are used to coat the yarns, the yarn surface would be
completely covered with the MXene flakes and the pathway to the
individual fibers would be blocked. This coating approach is useful
when the conductivity is the priority for the application. This
uniform, continuous and thin MXene coating on the yarn surface is
ideal for electromagnetic interference (EMI) shielding
applications. On the other hand, in case of electrochemistry
applications, the ion diffusion is poor.
[0033] Coating with small and large flakes: combines the two
methods described above to maximize the MXene loading both on the
fiber and the yarn level. For instance, maximum amount of MXene
coating is desirable for supercapacitors since the specific
capacitance is directly proportional to the active material
loading.
[0034] Electrochemical performance of MXene coated cotton yarns
were evaluated using a standard three-electrode set-up with 1 M
H.sub.2SO.sub.4 electrolyte. After evaluating the performance of
MXene coated cotton yarns, yarn supercapacitors (YSC) are
fabricated by using symmetric device configuration where both of
the electrodes have the same amount of MXene loading. To the best
of the inventors' knowledge, the cotton yarn with 2.2 mg/cm of
MXene loading exhibits the highest specific capacitance among the
cellulose-based yarn-shape supercapacitors reported to date. These
capacitance values achieved from MXene-cotton yarns are higher or
at the upper bound of the highest reported values among best
performance yarn supercapacitors in the literature.
[0035] The yarns have shown the ability to withstand prolonged
exposure to aqueous environments, a critical requirement for use in
textile devices. MXene coated cotton yarns can withstand high
washing temperatures (from 30.degree. C. to 80.degree. C.) for 45
washing cycles. Additionally, textiles from MXene-coated yarns have
been produced on industrial machine.
[0036] Textile Devices Made of MXene Coated Yarns
[0037] As a proof of concept, MXene coated bamboo yarns are knitted
into a pressure sensor device using an industrial knitting machine.
The sensor exhibits a constant (linear) gauge factor value of
.about.6 at applied strains of up to .about.20% and demonstrates a
high stability and linearity during the cyclic test (2000 cycles).
The inventors manufactured this technology by using conductive
MXene yarns and non-conductive commercial yarns through
conventional knitting machines without the need of sewing or gluing
conductive parts.
[0038] In addition to the pressure sensor, we demonstrated the
feasibility of a textile interdigitated supercapacitor and
triboelectric generator, and electromagnetic interference (EMI)
shielding fabric devices with MXene coated yarns.
[0039] Advantages and Impact
[0040] Nanomaterials have been incorporated into yarns via a
variety of methods, including dip-coating, drop-casting, and
biscrolling, and processed into fibers via wet-spinning and
electrospinning. The dip-coating process is the most facile,
simple, scalable, and environmentally friendly (no organic solvent
required) method among others.
[0041] Conductive yarns are widely used in smart textile
applications to provide properties like sensing, capacitance and
more. Demonstrating the processability of these conductive yarns is
crucial because high electrical conductivity, electrochemical, and
electromechanical performance do not necessarily mean that the
yarns can undergo industrial knitting or weaving processes. In
order to produce true textile devices, the conductive yarns need to
be knittable or weavable on industrial equipment. In this
invention, we demonstrate that textile using MXene coated yarns can
be produced on industrial equipment. MXene composite yarns produced
with other methods (electrospinning, biscrolling, etc.) are not
currently strong enough to be knitted or woven on industrial
machines.
[0042] The MXene coated yarns demonstrate excellent washability
over 45 washing cycles at temperatures ranging from 30.degree. C.
to 80.degree. C.
[0043] A textile pressure sensor device as knitted with MXene
coated yarns. This is the first wearable device produced with MXene
yarns that does not require any post-processing to demonstrate its
feasibility.
[0044] MXenes
[0045] MXene compositions may comprise any of the compositions
described elsewhere herein. Exemplary MXene compositions include
those comprising:
[0046] (a) at least one layer having first and second surfaces,
each layer described by a formula M.sub.n+1X.sub.nT.sub.x and
comprising:
[0047] substantially two-dimensional array of crystal cells, each
crystal cell having an empirical formula of M.sub.n+1X.sub.n, such
that
[0048] each X is positioned within an octahedral array of M,
wherein
[0049] M is at least one Group IIIB, IVB, VB, or VIB metal or Mn,
wherein
[0050] each X is C, N, or a combination thereof;
[0051] n=1, 2, or 3; and wherein
[0052] T.sub.x represents surface termination groups; or
[0053] (b) at least one layer having first and second surfaces,
each layer comprising:
[0054] a substantially two-dimensional array of crystal cells,
[0055] each crystal cell having an empirical formula of
M'.sub.2M''.sub.nX.sub.n+1T.sub.x, such that each X is positioned
within an octahedral array of M' and M'', and where M''.sub.n are
present as individual two-dimensional array of atoms intercalated
between a pair of two-dimensional arrays of M' atoms,
[0056] wherein M' and M'' are different Group IIIB, IVB, VB, or VIB
metals,
[0057] wherein each X is C, N, or a combination thereof;
[0058] n=1 or 2; and wherein
[0059] T.sub.x represents surface termination groups In certain of
these exemplary embodiments, the at least one of said surfaces of
each layer has surface termination groups (T.sub.x) comprising
alkoxide, carboxylate, halide, hydroxide, hydride, oxide,
sub-oxide, nitride, sub-nitride, sulfide, thiol, or a combination
thereof. In certain preferred embodiments, the MXene composition
has an empirical formula of Ti.sub.3C.sub.2.
[0060] While the instant disclosure describes the use of
Ti.sub.3C.sub.2, because of the convenient ability to prepare
larger scale quantities of these materials, it is believed and
expected that all other MXenes will perform similarly, and so all
such MXene compositions are considered within the scope of this
disclosure. In certain embodiments, the MXene composition is any of
the compositions described in at least one of U.S. patent
application Ser. No. 14/094,966 (filed Dec. 3, 2013), 62/055,155
(filed Sep. 25, 2014), 62/214,380 (filed Sep. 4, 2015), 62/149,890
(filed Apr. 20, 2015), 62/127,907 (filed Mar. 4, 2015) or
International Applications PCT/US2012/043273 (filed Jun. 20, 2012),
PCT/US2013/072733 (filed Dec. 3, 2013), PCT/US2015/051588 (filed
Sep. 23, 2015), PCT/US2016/020216 (filed Mar. 1, 2016), or
PCT/US2016/028,354 (filed Apr. 20, 2016), preferably where the
MXene composition comprises titanium and carbon (e.g.,
Ti.sub.3C.sub.2, Ti.sub.2C, Mo.sub.2TiC.sub.2, etc.). Each of these
compositions is considered independent embodiment. Similarly, MXene
carbides, nitrides, and carbonitrides are also considered
independent embodiments. Various MXene compositions are described
elsewhere herein, and these and other compositions, including
coatings, stacks, laminates, molded forms, and other structures,
described in the above-mentioned references are all considered
within the scope of the present disclosure.
[0061] Where the MXene material is present as a coating on a
conductive or non-conductive substrate, that MXene coating may
cover some or all of the underlying substrate material. Such
substrates may be virtually any conducting or non-conducting
material, though preferably the MXene coating is superposed on a
non-conductive surface. Such non-conductive surfaces or bodies may
comprise virtually any non-electrically conducting organic or
inorganic polymers. In independent embodiments, the substrate may
be a non-porous, porous, microporous, or aerogel form of an organic
polymer, for example, a fluorinated or perfluorinated polymer
(e.g., PVDF, PTFE) or an alginate polymer, a silicate glass.
[0062] The coating may be patterned or unpatterned on the
substrate. In independent embodiments, the coatings may be applied
or result from the application by spin coating, dip coating, roller
coating, compression molding, doctor blading, ink printing,
painting or other such methods. Multiple coatings of the same or
different MXene compositions may be employed.
[0063] The methods described in PCT/US2015/051588 (filed Sep. 23,
2015), incorporated by reference herein at least for such
teachings, are suitable for such applications.
[0064] In independent embodiments, the MXene coating can be present
and is operable, in virtually any thickness, from the nanometer
scale to hundreds of microns. Within this range, in some
embodiments, the MXene may be present at a thickness ranging from
1-2 nm to 1000 microns, or in a range defined by one or more of the
ranges of from 1-2 nm to 25 nm, from 25 nm to 50 nm, from 50 nm to
100 nm, from 100 nm to 150 nm, from 150 nm to 200 nm, from 200 nm
to 250 nm, from 250 nm to 500 nm, from 500 nm to 1000 nm, from 1000
nm to 1500 nm, from 1500 nm to 2500 nm, from 2500 nm to 5000 nm,
from 5 .mu.m to 100 .mu.m, from 100 .mu.m to 500 .mu.m, or from 500
.mu.m to 1000 .mu.m.
[0065] Typically, in such coatings, the MXene is present as an
overlapping array of two or more overlapping layers of MXene
platelets oriented to be essentially coplanar with the substrate
surface. In specific embodiments, the MXene platelets have at least
one mean lateral dimension in a range of from about 0.1 micron to
about 50 microns, or in a range defined by one or more of the
ranges of from 0.1 microns to 2 microns, from 2 microns to 4
microns, from 4 microns to 6 microns, from 6 microns to 8 microns,
from 8 microns to 10 microns, from 10 microns to 20 microns, from
20 microns to 30 microns, from 30 microns to 40 microns, or from 40
microns to 50 microns.
Terms
[0066] In the present disclosure the singular forms "a," "an," and
"the" include the plural reference, and reference to a particular
numerical value includes at least that particular value, unless the
context clearly indicates otherwise. Thus, for example, a reference
to "a material" is a reference to at least one of such materials
and equivalents thereof known to those skilled in the art, and so
forth.
[0067] When a value is expressed as an approximation by use of the
descriptor "about," it will be understood that the particular value
forms another embodiment. In general, use of the term "about"
indicates approximations that can vary depending on the desired
properties sought by the disclosed subject matter and is to be
interpreted in the specific context in which it is used, based on
its function. The person skilled in the art will be able to
interpret this as a matter of routine. In some cases, the number of
significant figures used for a particular value may be one
non-limiting method of determining the extent of the word "about."
In other cases, the gradations used in a series of values may be
used to determine the intended range available to the term "about"
for each value. Where present, all ranges are inclusive and
combinable. That is, references to values stated in ranges include
every value within that range.
[0068] It is to be appreciated that certain features of the
disclosure which are, for clarity, described herein in the context
of separate embodiments, may also be provided in combination in a
single embodiment. That is, unless obviously incompatible or
specifically excluded, each individual embodiment is deemed to be
combinable with any other embodiment(s) and such a combination is
considered to be another embodiment. Conversely, various features
of the disclosure that are, for brevity, described in the context
of a single embodiment, may also be provided separately or in any
sub-combination. Finally, while an embodiment may be described as
part of a series of steps or part of a more general structure, each
said step may also be considered an independent embodiment in
itself, combinable with others.
[0069] When a list is presented, unless stated otherwise, it is to
be understood that each individual element of that list, and every
combination of that list, is a separate embodiment. For example, a
list of embodiments presented as "A, B, or C" is to be interpreted
as including the embodiments, "A," "B," "C," "A or B," "A or C," "B
or C," or "A, B, or C."
[0070] The transitional terms "comprising," "consisting essentially
of," and "consisting" are intended to connote their generally in
accepted meanings in the patent vernacular; that is, (i)
"comprising," which is synonymous with "including," "containing,"
or "characterized by," is inclusive or open-ended and does not
exclude additional, unrecited elements or method steps; (ii)
"consisting of" excludes any element, step, or ingredient not
specified in the claim; and (iii) "consisting essentially of"
limits the scope of a claim to the specified materials or steps
"and those that do not materially affect the basic and novel
characteristic(s)" of the claimed disclosure. Embodiments described
in terms of the phrase "comprising" (or its equivalents), also
provide, as embodiments, those which are independently described in
terms of "consisting of" and "consisting essentially of" Where the
term "consisting essentially of" is used, the basic and novel
characteristic(s) of the method is intended to be the ability to
provide ordered perovskite, perovskite-type, and perovskite-like
films using MXene materials, which exhibit the crystallinity and
properties described herein.
[0071] Throughout this specification, words are to be afforded
their normal meaning, as would be understood by those skilled in
the relevant art. However, so as to avoid misunderstanding, the
meanings of certain terms will be specifically defined or
clarified.
[0072] While MXene compositions include any and all of the
compositions described in the patent applications and issued
patents described above, in some embodiments, MXenes are materials
comprising or consisting essentially of a M.sub.n+1X.sub.n(T.sub.x)
composition having at least one layer, each layer having a first
and second surface, each layer comprising
[0073] a substantially two-dimensional array of crystal cells.
[0074] each crystal cell having an empirical formula of
M.sub.n+1X.sub.n, such that each X is positioned within an
octahedral array of M,
[0075] wherein M is at least one Group 3, 4, 5, 6, or 7, or Mn,
[0076] wherein each X is carbon and nitrogen or combination of both
and
[0077] n=1, 2, or 3;
[0078] wherein at least one of said surfaces of the layers has
surface terminations, T.sub.s, independently comprising alkoxide,
alkyl, carboxylate, halide, hydroxide, hydride, oxide, sub-oxide,
nitride, sub-nitride, sulfide, sulfonate, thiol, or a combination
thereof;
[0079] As described elsewhere within this disclosure, the
M.sub.n+1X.sub.n(T.sub.x) materials produced in these methods and
compositions have at least one layer, and sometimes a plurality of
layers, each layer having a first and second surface, each layer
comprising a substantially two-dimensional array of crystal cells;
each crystal cell having an empirical formula of M.sub.n+1X.sub.n,
such that each X is positioned within an octahedral array of M,
wherein M is at least one Group 3, 4, 5, 6, or 7 metal
(corresponding to Group IIIB, IVB, VB, VIB or VIIB metal or Mn),
wherein each X is C and/or N and n=1, 2, or 3; wherein at least one
of said surfaces of the layers has surface terminations, T.sub.s,
comprising alkoxide, alkyl, carboxylate, halide, hydroxide,
hydride, oxide, sub-oxide, nitride, sub-nitride, sulfide,
sulfonate, thiol, or a combination thereof.
[0080] Supplementing the descriptions above,
M.sub.n+1X.sub.n(T.sub.x), compositions may be viewed as comprising
free standing and stacked assemblies of two dimensional crystalline
solids. Collectively, such compositions are referred to herein as
"M.sub.n+1X.sub.n(T.sub.x)," "MXene," "MXene compositions," or
"MXene materials." Additionally, these terms
"M.sub.n+1X.sub.n(T.sub.x)," "MXene," "MXene compositions," or
"MXene materials" also refer to those compositions derived by the
chemical exfoliation of MAX phase materials, whether these
compositions are present as free-standing 2-dimensional or stacked
assemblies (as described further below). Reference to the carbide
equivalent to these terms reflects the fact that X is carbon, C, in
the lattice. Such compositions comprise at least one layer having
first and second surfaces, each layer comprising: a substantially
two-dimensional array of crystal cells; each crystal cell having an
empirical formula of M.sub.n+1X.sub.n, where M, X, and n are
defined above. These compositions may be comprised of individual or
a plurality of such layers. In some embodiments, the
M.sub.n+1X.sub.n(T.sub.x) MXenes comprising stacked assemblies may
be capable of, or have atoms, ions, or molecules, that are
intercalated between at least some of the layers. In other
embodiments, these atoms or ions are lithium. In still other
embodiments, these structures are part of an energy-storing device,
such as a battery or supercapacitor. In still other embodiments
these structures are added to polymers to make polymer
composites.
[0081] The term "crystalline compositions comprising at least one
layer having first and second surfaces, each layer comprising a
substantially two-dimensional array of crystal cells" refers to the
unique character of these MXene materials. For purposes of
visualization, the two-dimensional array of crystal cells may be
viewed as an array of cells extending in an x-y plane, with the
z-axis defining the thickness of the composition, without any
restrictions as to the absolute orientation of that plane or axes.
It is preferred that the at least one layer having first and second
surfaces contain but a single two-dimensional array of crystal
cells (that is, the z-dimension is defined by the dimension of
approximately one crystal cell), such that the planar surfaces of
said cell array defines the surface of the layer; it should be
appreciated that real compositions may contain portions having more
than single crystal cell thicknesses.
[0082] That is, as used herein, "a substantially two-dimensional
array of crystal cells" refers to an array which preferably
includes a lateral (in x-y dimension) array of crystals having a
thickness of a single cell, such that the top and bottom surfaces
of the array are available for chemical modification.
[0083] Metals of Group 3, 4, 5, 6, or 7 (corresponding to Group
IIIB, IVB, VB, VIB, or VIIB), either alone or in combination, said
members including Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. For the
purposes of this disclosure, the terms "M" or "M atoms," "M
elements," or "M metals" may also include Mn. Also, for purposes of
this disclosure, compositions where M comprises Ti, Zr, Hf, V, Nb,
Ta, Cr, Mo, W, or mixtures thereof constitute independent
embodiments. Similarly, the oxides of M may comprise any one or
more of these materials as separate embodiments. For example, M may
comprise any one or combination of Hf, Cr, Mn, Mo, Nb, Sc, Ta, Ti,
V, W, or Zr. In other preferred embodiments, the transition metal
is one or more of Ti, Zr, V, Cr, Mo, Nb, Ta, or a combination
thereof. In even more preferred embodiments, the transition metal
is Ti, Ta, Mo, Nb, V, Cr, or a combination thereof. Specific MXene
metals may be used to provide dopant effects in the perovskite,
perovskite-type, or perovskite-like lattices, or may be chosen to
be chemically identical to one or more of the perovskite,
perovskite-type, or perovskite-like lattices.
[0084] In certain specific embodiments, M.sub.n+1X.sub.n comprises
M.sub.n+1C.sub.n (i.e., where X.dbd.C, carbon) which may be
Ti.sub.2C, V.sub.2C, V.sub.2N, Cr.sub.2C, Zr.sub.2C, Nb.sub.2C,
Hf.sub.2C, Ta.sub.2C, Mo.sub.2C, Ti.sub.3C.sub.2, V.sub.3C.sub.2,
Ta.sub.3C.sub.2, Mo.sub.3C.sub.2, (Cr.sub.2/3
Ti.sub.1/2).sub.3C.sub.2, Ti.sub.4C.sub.3, V.sub.4C.sub.3,
Ta.sub.4C.sub.3, Nb.sub.4C.sub.3, or a combination thereof.
[0085] In more specific embodiments, the M.sub.n+1X.sub.n(T.sub.x)
crystal cells have an empirical formula Ti.sub.3C.sub.2 or
Ti.sub.2C. In certain of these embodiments, at least one of said
surfaces of each layer of these two dimensional crystal cells is
coated with surface terminations, T.sub.s, comprising alkoxide,
fluoride, hydroxide, oxide, sub-oxide, sulfonate, or a combination
thereof.
[0086] The range of compositions available can be seen as extending
even further when one considers that each M-atom position within
the overall M.sub.n+1X.sub.n matrix can be represented by more than
one element. That is, one or more type of M-atom can occupy each
M-position within the respective matrices. In certain exemplary
non-limiting examples, these can be
(M.sup.A.sub.xM.sup.B.sub.y).sub.2C,
(M.sup.A.sub.xM.sup.B.sub.y).sub.3C.sub.2, or
(M.sup.A.sub.xM.sup.B.sub.y).sub.4C.sub.3, where M.sup.A and
M.sup.B are independently members of the same group, and x+y=1. For
example, in but one non-limiting example, such a composition can be
(V.sub.1/2Cr.sub.1/2).sub.3C.sub.2.
[0087] As those skilled in the art will appreciate, numerous
modifications and variations of the present disclosure are possible
in light of these teachings, and all such are contemplated
hereby.
[0088] The disclosures of each patent, patent application, and
publication cited or described in this document are hereby
incorporated herein by reference, each in its entirety, for all
purposes, or at least for the purpose described in the context in
which the reference was presented.
Additional Disclosure
[0089] There are various approaches in the literature to produce
conductive and electrochemically active fibers and yarns. One
common technique is the deposition of active material(s) onto a
fiber/yarn substrate. This method is easily scalable and offers
facile approach for incorporating various active materials into
yarns. However, loading more than 30 wt. % of active material onto
a fiber has remained a challenge for this method, resulting in
fibers with low electrical conductivity and moderate
electrochemical properties.
[0090] These results indicate the need for a more efficient coating
approach that maximizes the active material loading while
preventing their delamination from the yarn substrate during wear
and washing. Wet-spinning has also been widely used to integrate
active materials such as conductive polymers, graphene, and carbon
nanotubes (CNTs) into fibers for energy storage and sensing
applications. A biscrolling technique has also been developed that
produces functional yarns by trapping active materials inside CNT
sheets. These techniques achieved high loadings (up to .about.97
wt. %) of active materials into fibers or yarns. However,
functional fibers or yarns produced using these methods seldom
offer the mechanical properties required by textile processing and
can be challenging to scale-up. In the context of wearables,
manufacturability of the yarns is crucial because high electrical
conductivity and electrochemical performance do not necessarily
correspond to the feasibility of industrial-scale knitting or
weaving processes. When considering the use of functional yarns in
truly wearable applications, washability also becomes important.
The ability to withstand prolonged exposure to aqueous environments
is necessary for practical applications because textiles undergo
various washing cycles after use.
[0091] The above limitations have led the inventors to develop
fabrication of knittable, washable, and highly conductive yarn
electrodes using MXenes. MXenes are a large family of
two-dimensional (2D) transition metal carbides and nitrides which
have a general formula of M.sub.n+1X.sub.nT.sub.x, where M is a
transition metal, X is carbon and/or nitrogen with n=1, 2, or 3,
and T.sub.x denotes the surface termination (--OH, --O, and --F).
MXenes have attracted significant attention due to their high
electrical conductivity (up to 10,000 S/cm as a thin film) and
excellent volumetric capacitance (up to 1,500 F/cm.sup.3). Their
hydrophilic surface, due to the presence of abundant functional
groups, makes them suitable for solution processing by
spray-coating, vacuum-assisted filtration, printing and painting
from aqueous solutions.
[0092] Ti.sub.3C.sub.2T.sub.x MXene (referred to as Ti.sub.3C.sub.2
for simplicity) has demonstrated exceptional cation intercalation
and pseudocapacitive behavior, which is ideal for energy storage
applications. Ti.sub.3C.sub.2 MXene is also biocompatible and does
not present a risk in case of contact with skin. Environmental
degradation or incineration of Ti.sub.3C.sub.2 produces titanium
dioxide (TiO.sub.2) and carbon dioxide (CO.sub.2), which do not
present threats to the environment.
[0093] By using Ti.sub.3C.sub.2 as an active material, we employed
a simple two-step dipping and drying procedure and converted
conventional cellulose-based yarns such as cotton, bamboo, and
linen into yarn electrodes. These MXene-coated yarns demonstrate
three orders of magnitude increase in electrical conductivity and
one order of magnitude increase in electrochemical performance when
compared to carbon materials. By optimizing the coating process and
carefully choosing appropriate MXene sheet size at each step of the
coating process, we achieve yarns with a high loading of 78 wt. %
MXene. We demonstrate that these yarns can be washed at
temperatures ranging from 30.degree. C. to 80.degree. C. for 45
washing cycles and with minimal decrease in conductivity. We
further show that for the first time, these yarns can be knitted
into various stitch patterns using an industrial scale knitting
machine, which were only achieved by simulation in previous reports
(FIG. 1). The electrochemical performance of MXene-coated cotton
yarns show that they have the potential to power wearable
electronics as yarn supercapacitor devices. We also demonstrated
that the knitted MXene-coated yarns can be used to make a flexible
and wearable capacitive pressure sensor. While the scope of this
work focuses on MXene-coated cellulose-based yarns and
demonstration of energy storage and pressure sensing applications,
these yarns offer electrical and electrochemical properties that
can meet the requirements of other applications such as in energy
harvesting, other types of sensors (e.g., strain, moisture, and
temperature), antennas, heaters, and electromagnetic interference
(EMI) shielding. Such functional yarns offer a platform technology,
which utilizes these conformal yarns to enable development of
various types of textile-based devices.
[0094] Results
[0095] Production of Conductive MXene-Coated Cellulose-Based
Yarns
[0096] The initial step in producing the MXene-coated yarns begins
with solution processing of MXene into homogenous dispersions (FIG.
2a). X-ray diffraction (XRD) results indicated the successful
etching of Al layers and exfoliation of MXene by the expansion and
disorder of the interlayer spacing according to the (002) peak
(FIG. 7a). The disappearance of the (014) peak in the resulting
Ti.sub.3C.sub.2 films indicated there is no residual MAX phase.
Transmission electron microscopy (TEM) studies confirmed the
synthesis of delaminated MXene nanosheets (small MXene flakes,
S--Ti.sub.3C.sub.2, Inset of FIG. 2b and the large MXene flakes,
L-Ti.sub.3C.sub.2, FIG. 7b). FIGS. 7c and 7d show an atomic force
microscopy (AFM) images of S--Ti.sub.3C.sub.2 and L-Ti.sub.3C.sub.2
MXene flakes, respectively. The concentration of the MXene
dispersions used during dipping was between 25-30 mg/mL.
[0097] MXene flakes are negatively charged and hydrophilic due to
their surface functional groups (e.g., --O, --OH, and --F). As
shown in FIG. 2b, the zeta potential of the Ti.sub.3C.sub.2 MXene
flakes was measured as -56 mV at pH 6.8. When hydrophilic cotton
yarns were dipped into negatively charged MXene dispersions, MXene
flakes attached to the surface of cotton fibers. As a result,
strong electrostatic interactions were established between MXene
flakes and cotton fibers. The XRD pattern for
Ti.sub.3C.sub.2-coated cotton yarn shows signatures of both
Ti.sub.3C.sub.2 MXene and cotton peaks (FIG. 7a). In order to
increase the overall active material loading during the dip-coating
process, MXene dispersions with two different flake size
distributions were used in this study: as-synthesized
(L-Ti.sub.3C.sub.2 MXene) and probe sonicated (S--Ti.sub.3C.sub.2
MXene). According to the dynamic light scattering (DLS) results
(FIG. 2c), L-Ti.sub.3C.sub.2 MXene dispersions were primarily
composed of large flakes with an average particle size of 1 .mu.m,
whereas the S--Ti.sub.3C.sub.2 MXene dispersions were composed of
nanoscale-sized flakes with an average particle size of 340 nm.
Scanning electron microscopy (SEM) images of S--Ti.sub.3C.sub.2 and
L-Ti.sub.3C.sub.2 MXene flakes (Inset of FIG. 2c) are in agreement
with the DLS data. It has been shown that L-Ti.sub.3C.sub.2 MXene
flakes result in higher electrical conductivity compared to
S--Ti.sub.3C.sub.2 MXene flakes, which is most likely due to less
interfacial resistance between L-Ti.sub.3C.sub.2 MXene flakes.
Films made by filtering L-Ti.sub.3C.sub.2 MXene flakes showed
higher electrical conductivity of 9490 S/cm, whereas the films
produced by filtering S--Ti.sub.3C.sub.2 MXene flakes resulted in
electrical conductivity of .about.4080 S/cm.
[0098] Three different approaches for producing conductive yarns
with MXene dispersions were studied: (1) coating with
S--Ti.sub.3C.sub.2 MXene, (2) L-Ti.sub.3C.sub.2 MXene, and (3)
combination of small and large flakes. The pristine cotton yarn
consists of twisted cotton fibers, which have a kidney-shaped
cross-section with a hollow core (lumen) as illustrated in FIG. 2d.
Unlike most synthetic yarns, cotton fibers have a rough surface
(FIG. 2g), which is ideal for nanoparticle adhesion. The first
coating process consisted of using only S--Ti.sub.3C.sub.2 MXene
dispersions to allow for small MXene flakes to infiltrate between
individual fibers (FIG. 2e, h). Using this coating method, the
cotton yarn retained its flexibility. The conductivity of
S--Ti.sub.3C.sub.2-coated cellulose-based yarns with MXene loadings
of 0.6 mg/cm was between 30 and 50 S/cm, which is sufficient for a
variety of applications such as pressure and strain sensing. The
second coating method utilized L-Ti.sub.3C.sub.2 MXene dispersions
to achieve MXene coating only on the surface of the yarn. When only
MXene dispersions with large flakes were used to coat the yarns,
the formation of MXene coating on the yarn surface prevented the
further infiltration of MXene flakes into the internal yarn
structure, thereby leaving the individual fibers closer to the
center uncoated. The conductivity of L-Ti.sub.3C.sub.2-coated
cellulose-based yarns ranges from 60 to 85 S/cm (MXene loading of
0.6 mg/cm), which is higher than the conductivity of the yarns
coated only with S--Ti.sub.3C.sub.2 MXene flakes. Even though
higher conductivity is achieved with L-Ti.sub.3C.sub.2-coated
cellulose-based yarns, the yarns become less flexible. Notably, as
the L-Ti.sub.3C.sub.2 MXene loading increased up to 0.6 mg/cm,
MXene coating easily delaminated from the yarn surface upon forming
the loops during knitting. Thus, the yarns coated with only
L-Ti.sub.3C.sub.2 MXene flakes were not integrated into functional
devices.
[0099] In order to balance the flexibility and the conductivity of
the MXene coated yarns, we first infiltrated the internal yarn
structure with S--Ti.sub.3C.sub.2 MXene in order to coat the
individual fibers before finally coating the external yarn with
L-Ti.sub.3C.sub.2 MXene. This approach, the two-step coating
process, maximizes the MXene loading by coating both on the fiber
and the yarn level.
[0100] In order to maximize MXene loading on the yarn, the fibers
were first saturated with S--Ti.sub.3C.sub.2 MXene flakes before
coating with L-Ti.sub.3C.sub.2 MXenes to cover the yarn surface
(FIG. 2f, i). This coating approach could be ideal for yarn and
textile supercapacitor applications since the capacitance has been
reported to be MXene loading dependent..sup.[10] The cotton yarn
surface after coating with only S--Ti.sub.3C.sub.2 (FIG. 2k)
remained similar to the pristine cotton (FIG. 2j) in terms of
flexibility because majority of the small flakes infiltrated into
the fiber. On the other hand, the twist became no longer visible
after coating with both S--Ti.sub.3C.sub.2 and L-Ti.sub.3C.sub.2
MXene dispersions (FIG. 2l), which created a continuous conductive
pathway along the yarn surface. The yarns produced via two-step dip
coating process were not as flexible as the yarns coated with only
S--Ti.sub.3C.sub.2 MXene dispersions.
[0101] However, they demonstrated easier knittability and less
flaking compared to the yarns coated with only L-Ti.sub.3C.sub.2
MXene dispersions. This is most likely due to a more balanced
weight distribution between the center and the outside of the yarn
achieved with the two-step dip coating process, where the presence
of S--Ti.sub.3C.sub.2 MXene flakes at the internal yarn structure
helped to balance the yarn's weight compared to only the presence
of cotton fibers when the yarn surface only coated with
L-Ti.sub.3C.sub.2 MXene dispersions. The same coating process was
also applied to bamboo and linen yarns to demonstrate the
adaptability of this method to other cellulose-based yarns. More
detailed cross-sectional SEM images of the pristine and
MXene-coated cotton, bamboo, and linen yarns are shown in FIG. 8.
The MXene-coated yarns were dried thoroughly in air and
subsequently placed in a vacuum desiccator prior to further
evaluation.
[0102] To determine the mass loading of MXene, each yarn was
weighed before and after dip-coating with MXene. The masses were
averaged from three skeins with 200 cm length in order to account
for mass variation along the length of the yarn. By following the
two-step coating procedure, the active mass loading of up to 78 wt.
% (2.5 mg/cm) could be achieved with cotton yarns. MXene-coated
bamboo and linen yarns showed similar MXene loadings of .about.75
wt. % (2.2 mg/cm) and .about.77 wt. % (2.2 mg/cm), respectively. To
the best of our knowledge, the active mass loading of .about.78 wt.
% deposited on the yarns is the highest reported value in the
literature for a facile, yarn dip-coating approach.
[0103] Investigation of the changes in resistance and conductivity
of the MXene-coated cellulose-based yarns with length (FIG. 9a)
revealed that the resistance increased linearly as a function of
yarn length, thus the conductivity remained unchanged when the yarn
length increased from .about.1 to .about.210 cm. At the highest
MXene loading of 78 wt. %, the conductivity of the MXene-coated
cotton yarn reached 198.5.+-.1.4 S/cm (1.7.+-.0.2 .OMEGA./cm, yarn
diameter .about.610 .mu.m). While bamboo yarns with 75 wt. % MXene
loading exhibited similar conductivity values with MXene-coated
cotton yarns, the conductivity of the linen yarns with 77 wt. %
MXene loading reached 440.3.+-.0.9 S/cm, which is .about.2.2-times
higher than MXene-coated cotton and bamboo yarns. Since linen yarns
possess the smallest diameter (.about.425 .mu.m) among all examined
yarns (.about.610 .mu.m for cotton and .about.570 .mu.m for
bamboo), the improved conductivity of the MXene-coated linen yarns
can be attributed to the .about.1.8-times higher MXene loading per
unit volume of the linen yarn compared to cotton and bamboo yarns.
Moreover, linen fibers (60-120 cm) are the longest fibers studied
in this paper when compared to cotton (1-4 cm) and bamboo (5-8 cm)
fibers. Similar to S--Ti.sub.3C.sub.2 vs. L-Ti.sub.3C.sub.2 MXene
flakes, longer fibers infiltrated with MXene flakes help to
decrease the overall interfacial resistance along the yarn length
by creating more effective conduction paths. Mechanical testing of
MXene-coated cellulose-based yarns at the maximum active material
loading (75-78 wt. %) shows that MXene addition also reinforces the
yarn, improving the mechanical properties (FIG. 9b). For instance,
at 78 wt. % MXene, the cotton yarn showed a Young's modulus of
5.0.+-.0.3 GPa and a tensile strength of 468.4.+-.27.1 MPa, which
were .about.7% and .about.40% higher than those of the pristine
cotton yarns, respectively. Moreover, MXene-coated cotton yarn (78
wt. % MXene loading) can form a knot (FIG. 9c), indicating good
flexibility and knittability. Thus, coating of cellulose-based
yarns with Ti.sub.3C.sub.2 MXene dispersions resulted in flexible
and mechanically stable yarns that offer good electrical
conductivity and high active material loading for a variety of
promising applications.
[0104] Knittability of MXene-Coated Cellulose-Based Yarns
[0105] We investigated the knittability of the MXene-coated
cellulose-based yarns, including cotton, linen, and bamboo into
full fabrics on an industrial machine using different stitch
patterns. Knitting, the intermeshing of yarn loops to form a
textile, was chosen due to its flexibility in programming and rapid
prototyping. During industrial knitting process, the yarns are
subjected to uniaxial tensile and bending stresses, making the
overall stress much higher in comparison to hand knitting. Knitting
cotton yarns coated with active materials with industrial machines
was not possible for a long time as discussed in previous
literature.
[0106] One of the reasons is that the cotton fibers are more likely
to pull apart from each other while under tension during knitting
since they consist of shorter fibers (1-4 cm) in comparison to
other cellulose-based yarns (5-8 cm for bamboo and 60-120 cm for
linen). The MXene-coated yarns are stronger and less flexible
compared to their pristine counterparts. We addressed their reduced
flexibility (after coating) by optimizing the stitch patterns
through extensive parametric studies.
[0107] Here, we successfully knitted MXene-coated cotton and other
cellulose-based yarns into swatches (fabric samples with 60
mm.times.65 mm in total area and 16 mm.times.26 mm in active area)
and investigated different stitch patterns (geometric construction
of the knitted loops) including single jersey (FIG. 3a), half-gauge
(FIG. 3b), and interlock (FIG. 3c). The stitch pattern dictates how
the yarns are inter-looped to create different knit structures.
Single jersey is the most common fabric type and simplest loop
structure among knitted textiles. However, it is not necessarily
the ideal stitch pattern when it comes to knitting the coated yarns
since these yarns exhibit lower flexibility compared to their
pristine states. In jersey knits, the loops are formed using every
needle adjacent to each other on the needle bed. This can result in
yarn-to-yarn rubbing and breakage due to a smaller bending radius
of the yarn during knitting (FIG. 3d). To prevent the yarn
breakage, a half-gauge pattern can be knitted. Half-gauge knit uses
every other needle on the bed in each machine pass, resulting in a
more porous fabric (FIG. 3e). The interlock pattern (FIG. 30, also
uses every other needle but knits all needles in two passes. Odd
needles (denoted with asterisks) are knitted in the first machine
pass and the even needles (denoted with triangles) are knitted
during the second pass of the sequence. The interlock pattern (FIG.
30 results in a fabric closer in density to single jersey and is
denser compared to the half-gauge pattern. Thus, utilization of
half-gauge and interlock stitch patterns increased the space
between each line of the loops and reduced the yarn-to-yarn
friction and yarn breakage. The ability to knit MXene-coated
cellulose-based yarns with different stitch patterns allowed us to
control the fabric properties such as porosity and thickness for
various applications. Understanding the properties and the
limitations of conductive yarns enabled us to adjust the stitch
patterns and the corresponding knitting parameters in order to knit
these yarns.
[0108] Washability of MXene-Coated Cellulose-Based Yarns
[0109] The ability of conducting fibers to withstand prolonged
exposure to aqueous environments is critical for use in wearable
applications. The impact of washing was studied using
Ti.sub.3C.sub.2-coated cotton yarns produced by the two-step
dip-coating process. S--Ti.sub.3C.sub.2 MXene was used to coat the
individual fibers in the internal yarn structure, then
L-Ti.sub.3C.sub.2 MXene was used to coat the external yarn surface.
The outer MXene coating thickness on the yarn surface was
15.2.+-.0.8 .mu.m based on the cross-sectional SEM images. The
MXene loading remained relatively unchanged (<1% decrease) after
45 hours of washing cycles at temperatures ranging from 30.degree.
C. to 80.degree. C., as shown in FIG. 4a. This is due to the strong
interactions between MXene flakes so that even vigorous shaking did
not redisperse the flakes as shown in free-standing films.
[0110] MXene-coated cotton yarns showed minimal change in linear
electrical resistance after 20 washing cycles at 30.degree. C. As
the washing temperature increased from 30.degree. C. to 80.degree.
C., the linear resistance increased only by .about.3%. SEM images
of the unwashed (FIG. S10a) and washed (FIG. 10b) MXene-coated
cotton yarns after 45 washing cycles revealed very little material
loss even after 45 h at elevated temperature in water. The washed
MXene-coated cotton yarns demonstrated similar mechanical
properties to the unwashed MXene-coated yarns with tensile strength
of 460.1.+-.25.2 MPa, Young's modulus of 4.8.+-.0.2 GPa, and
failure at strain value of 0.0844.+-.0.004. This result is the
first to demonstrate the negligible detrimental effect of washing
MXene-coated yarns on their mechanical properties.
[0111] X-ray photoelectron spectroscopy (XPS) was used to
investigate if the washing process resulted in oxidation or
degradation of MXene. XPS is inherently a surface sensitive
technique due to the shallow escape depth of the photoelectrons
generated from the material, therefore, the spectra gathered are
indicative of only the outer <15 nm surface layer. FIG. 4b
showed that the MXene in the unwashed fibers exhibited very low
degree of oxidation whereby .about.7.3 at % of Ti in MXene was in
the form of Ti.sup.4+ (indicative of TiO.sub.2) which is the
product of Ti.sub.3C.sub.2 MXene oxidation. After washing the yarns
at 30.degree. C. for 20 washing cycles followed by 25 washing
cycles from 40 to 80.degree. C., the MXene in the thin outer
surface layer was oxidized with the Ti.sup.4+ comprising
.about.43.6 at % (FIG. 10c). After sputtering for just 3 mins, the
measured degree of oxidation decreased to .about.24.6 at % (FIG.
4c). Bulk properties, such as electrical conductivity, are often
governed by the overall state of the material. The resistance of
the MXene-coated cotton yarn increased by less than 5% after
washing at temperatures ranging from 30.degree. C. to 80.degree. C.
for 45 washing cycles, as shown in FIG. 4a. Partial surface
oxidation (<1 .mu.m in thickness compared to .about.15.2 .mu.m
in thickness of the external MXene layer) does not seem to
significantly affect the overall conductivity of the yarns. The
remaining MXene flakes in both the fiber and the yarn levels are
able to provide similar conductivity values to unwashed
MXene-coated cotton yarn. The summary of the high-resolution
Ti.sub.2p XPS region is provided in Table 1 herein for unwashed and
washed MXene-coated cotton yarns before and after sputtering. These
results further support our findings of the stability of
MXene-coated cotton yarns under harsh environments. Unlike the
colloidal MXene dispersions, once the MXene flakes are assembled
and dried, there are no more reactive pathways for oxidation
because additional water cannot easily rehydrate the structure. As
a result, the exposure to water and temperature does not seem to
affect the overall electrical conductivity of the MXene-coated
cotton yarns as observed in case of assembled MXene flakes in
films.
[0112] Electrochemical Properties of MXene-Coated Cotton Yarns
[0113] Electrochemical performance of MXene-coated cotton yarns was
evaluated using a standard three-electrode set-up with 1 M
H.sub.2SO.sub.4 electrolyte to assess the feasibility of using
these yarns for energy storage applications. Cotton yarn with 78
wt. % (2.5 mg/cm) of MXene loading was used as the working
electrode without any current collector during the test. Using
cyclic voltammetry (CV), the stable potential range for the
MXene-coated cotton yarns was identified to be between -0.55 and
0.25 V versus Ag/AgCl (FIG. 5a). The representative CV and
galvanostatic charge-discharge (GCD) curves of the MXene-coated
cotton yarns at different scan rates and current densities were
shown in FIGS. 5b and 5c, respectively. The CV curves demonstrated
a quasi-rectangular shape with close to .about.100% Coulombic
efficiency under anodic potential at all scan rates indicating the
capacitive behavior of MXene-coated cotton yarns. An increased
capacitance under high cathodic potentials is due to H.sup.+
induced redox behavior of Ti.sub.3C.sub.2 (pseudo-capacitance). The
GCD curves at different current densities, are highly symmetrical
even at high discharge current density of 24 mA/cm. The specific
capacitances as a function of scan rates were determined using CV
curves as shown in FIG. 5d. The specific capacitance decay as a
function of scan rate was most likely to be due to the diffusion
limitations of the ionic transport. Similar
intercalation/deintercalation rate limitation was also observed in
case of thick planar MXene electrodes. The MXene-coated cotton yarn
displayed a length capacitance (C.sub.L) of .about.759.5 mF/cm at 2
mV/s. The areal capacitance (C.sub.A) and volumetric capacitance
(C.sub.V) values were also calculated from CV curves at 2 mV/s as
.about.3965.0 mF/cm.sup.2 and .about.260.0 mF/cm.sup.3,
respectively. Gravimetric capacitance (C.sub.G) is dependent on the
thickness and density of the electrodes as well as weight of the
other components, which results in unreliable comparison between
different supercapacitors. However, mass is an important parameter
and cannot be neglected. Both the gravimetric (mass) and the
linear, areal, or volumetric capacitances need to be considered
when evaluating the capacitance performance. Tex, mass of the yarn
in grams per 1,000 meter, is a common metric used in the textile
industry. It takes into consideration both the mass and the length
of the yarns to avoid the faulty assumption of yarns being perfect
cylinders with fixed diameters. The linear density of the cotton
yarns at 2.5 mg/cm MXene loading (mass of the pristine cotton yarn
.about.0.7 mg/cm) was measured as 320 Tex. Thus, the linear density
capacitance of the electrode (C.sub.Tex) was 2.1 mF/Tex at 2 mV/s.
To the best of authors' knowledge, the cotton yarns with 78 wt. %
MXene loading exhibited the highest specific length capacitance
among the cellulose-based yarn-shaped supercapacitors reported to
date.
[0114] Electrochemical impedance spectroscopy (EIS) was conducted
to understand the charge transfer and ion transport properties of
the MXene-coated cotton yarns. As shown in FIG. 5e, the equivalent
series resistance (ESR) was calculated as 1.8 .OMEGA./cm from the
high frequency intercept of the Nyquist plot. MXene-coated cotton
yarns showed a short Warburg region with a 45.degree. angle, which
indicated good ion diffusion efficiency, and a linear behavior in
the low-frequency region, demonstrating close to the ideal
capacitive behavior. As shown in FIG. 5f, MXene-coated cotton yarns
exhibited excellent cyclic stability with 100% Coulombic efficiency
after 10,000 cycles at a current density of 30 mA/cm. It should be
noted that the MXene coated cotton yarn electrode has not been
precycled prior to the cyclability test and the .about.5% increase
in capacitance stabilized back to 100% retention after .about.2,000
cycles. This result shows that for practical applications, the
textile supercapacitors built using MXene-coated cotton electrodes
need to be preconditioned prior to use. SEM images (FIG. 11) of the
MXene-coated cotton yarns before and after 10,000 cycles show that
the morphology of the yarns as well as the MXene coating remained
almost unchanged.
[0115] The electrochemical results indicate that MXene-coated
cotton yarns can be a potential candidate in powering wearable
electronics. They can be incorporated into symmetric yarn
supercapacitors to offer sufficient energy and power for a variety
of applications. To demonstrate this, yarn supercapacitors were
fabricated using a symmetric device configuration where both of the
electrodes had the same amount of MXene loading. The electrodes
were separated by a polyvinyl alcohol (PVA)--H.sub.2SO.sub.4 gel
electrolyte. The voltage window was kept at 0.6 V to prevent the
oxidation of Ti.sub.3C.sub.2 MXene as suggested by previous
studies. From the CV curves shown in FIG. 12a, the specific
capacitance values of the device (at 2 mV/s) were calculated as
C.sub.L of .about.306.9 mF/cm (0.6 mF/Tex), CA of .about.1865.3
mF/cm.sup.2, and C.sub.V of .about.142.4 mF/cm.sup.3. The GCD
curves (FIG. 12b) are highly symmetric at all current densities
investigated with negligible iR drop. The rate handling of the
symmetric yarn supercapacitor device shown in FIG. 12b can be
adjusted by using a yarn electrode with smaller diameter, which
would reduce the overall thickness of the device and improve the
ion diffusion at higher scan rates. The Nyquist plot (FIG. 12d)
showed nearly vertical behavior at all frequencies, suggesting fast
ion diffusion with an estimated ESR value of 7.1 .OMEGA./cm. The
yarn supercapacitor device showed a long-term capacitance retention
of .about.100% after 10,000 charge-discharge cycles while
maintaining 100% Coulombic efficiency (FIG. 12e) when tested with
GCD cycles at 5 mA/cm. Further increase in the voltage window and
energy storage can be achieved by using organic electrolyte. The
stability and performance of free-standing yarn supercapacitor
devices (5 cm long) were also tested under bending cycles at
various bending angles as shown in FIG. 11f. The device
demonstrated stable response with a .about.100% capacitance
retention after 1,000 cycles when bent at 90.degree.. The
performance of the device remained stable when repeated
deformations were applied during the test.
[0116] Knitted Capacitive Pressure Sensor Device
[0117] To demonstrate multifunctionality of MXene-coated yarns, we
also used them to make a textile pressure sensor device. Since
MXene-coated cotton yarns were used to demonstrate the feasibility
of energy storage applications, MXene-coated bamboo yarns have been
chosen for the pressure sensor device assembly. We knitted
MXene-coated bamboo yarns (MXene loading 0.6 mg/cm) into a
rectangular swatch (16 mm by 26 mm) surrounded by a knitted viscose
yarn using interlock stitch (FIG. 6a). The capacitive textile
sensor device was then prepared by carefully placing two identical
knitted swatches on top of each other with a dielectric layer of
thin nitrile rubber sandwiched in between. The electromechanical
measurement of the textile sensor showed that the capacitance (C)
increased with compression strain (FIG. 6b) and applied stress
(FIG. 13a), and returned to initial value (C.sub.0) when released.
The capacitance response of the sensor as a function of various
magnitudes of cyclic compression strains (FIG. 6c) showed that the
textile sensor was able to respond to a wide range of compression
strains (.epsilon.) from 2.8% to 19.7%, equivalent to pressures of
0.002 and 66 kPa (per whole sensor area, not considering textile
porosity), respectively. Notably, the relative change in
capacitance (.DELTA.C/C.sub.0) showed a linear relationship with
the magnitude of compression strain, indicating the linearity of
the sensing response (FIG. 6d). Fitting a linear line to
.DELTA.C/C.sub.0 vs. .epsilon. data, revealed a slope of 6.02. This
slope corresponds to the gauge factor (GF) of the sensor, defined
as .DELTA.C/.epsilon.C.sub.0. GF is an important sensing metric as
it determines the sensitivity of the sensor device. This GF is
comparable to other capacitive textile-based pressure sensors,
indicating the high sensitivity of the knitted MXene-coated yarn
pressure sensor device. When repeatedly compressed and relaxed for
2,000 cycles at 14.1% strain, the capacitive response of the
textile device remained constant (FIG. 6e), indicating excellent
cyclic stability. This long-term sensing stability demonstrates
that the sensor's response is reproducible.
[0118] We also prepared a capacitive pressure sensor button (FIG.
6f) by knitting the MXene-coated yarn into fully functional device,
i.e. two textile electrodes and a sandwiched dielectric layer, in
one step using an industrial-scale knitting machine. The knitted
pressure sensor button was capable of sensing various levels of
finger pressures and weights. For instance, the capacitance
response of the sensor increased approximately two, three, and four
times its initial value when gentle, moderate, and hard pressures
were applied, respectively (FIG. 60. Moreover, 20% and 50%
increases in the capacitance response were observed when 5 g and 20
g weights were placed on the textile device, respectively (FIG.
13b). These examples show that the knitted fabric sensor is capable
of distinguishing various levels of applied pressures and can may
be used in practical applications. The performance of the knitted
pressure sensor can be further improved in the future by changing
the yarn type, stitch pattern, active material loading, and the
dielectric layer to result in higher capacitance changes under
applied pressure to achieve more reliable devices for wearable
applications.
[0119] This work introduced a simple two-step dip-coating process
using colloidal solutions of small- and large-size Ti.sub.3C.sub.2
MXene flakes, which transformed traditional cellulose-based yarns
into highly conductive, electrochemically and electromechanically
active yarns. MXene loadings of up to 77 wt. % (2.2 mg/cm) were
achieved, which resulted in yarns with a remarkable electrical
conductivity of up to 440.3.+-.0.9 S/cm. By adjusting the stitch
pattern between single jersey, half-gauge and interlock,
MXene-coated cellulose-based yarns were successfully knitted into
full fabrics using an industrial knitting machine. When washed at
temperatures ranging from 30.degree. C. to 80.degree. C., the MXene
loading remained almost unchanged with negligible change in the
yarn resistance and conductivity. The MXene-coated cotton yarn
exhibited a high length capacitance (C.sub.L) of up to 759.5 mF/cm
(2.1 mF/Tex). The C.sub.L of 306.9 mF/cm (0.5 mF/Tex) at 2 mV/s was
achieved when two MXene-coated cotton yarns were assembled into
free-standing, symmetric yarn supercapacitor. By using the knitted
MXene-coated bamboo yarns as electrodes, we achieved a
textile-based capacitive pressure sensor that demonstrated a high
sensitivity (GF .about.6.02), a sensing range of 20% compression,
and excellent cycling stability at .about.14.1% strain for 2,000
cycles. The MXene-coated yarns offer suitable properties that can
meet the performance requirements of applications other than energy
storage and sensing, such as triboelectric energy harvesting, EMI
shielding, and heated fabrics. The established approach in this
study, which combines the versatile chemistry and promising
electrical and electrochemical properties of MXenes with the
existing cellulose-based yarns, offers a platform technology for
various textile-based devices by allowing tunability in performance
for the building blocks of textiles.
[0120] Experimental Section
[0121] Synthesis of Ti.sub.3C.sub.2Tx MXene:
[0122] Ti.sub.3AlC.sub.2 MAX phase powder was synthesized according
to the method described previously. Ti.sub.3C.sub.2 was synthesized
by selective etching of Al atomic layers from Ti.sub.3AlC.sub.2 MAX
phase. To prepare the MXene dispersion, 3 g of Ti.sub.3AlC.sub.2
was added slowly to a 60 mL of chemical etchant (6:3:1 ratio)
consisting of 36 mL of 12 M hydrochloric acid (HCl, Alfa Aesar,
98.5%), 18 mL of deionized (DI) water, and 6 mL of hydrofluoric
acid (HF, Acros Organics, 49.5 wt. %). The mixture was stirred at
500 rpm for 24 h at room temperature. After etching, the solution
was washed by repeated centrifugation at 3,500 rpm for 5 min
cycles. The acidic supernatant was decanted after centrifuging and
DI water was then added to wash the MXene powder several times
until its pH reached .about.5-6.
[0123] Delamination and Preparation of MXene:
[0124] For delamination, 2 g of lithium chloride (LiCl, Chem-Impex
Int., 99.3%) dissolved in 100 mL of DI water was added to the
sediment after washing. The lithium-ions intercalate between the
interlayer spacings of multilayered MXene to facilitate subsequent
delamination into few layered sheets. The mixture was first
dispersed by manual shaking and then stirred at room temperature
for 4 hours. The MXene solution was then washed four times by
centrifugation until the supernatant was dark, indicating
delamination. To separate unreacted Ti.sub.3AlC.sub.2 MAX and
multi-layer Ti.sub.3C.sub.2 MXene flakes, centrifugation at 3,500
rpm for 5 min was repeated. The supernatant was collected, and the
sediment was redispersed with more water before beginning the next
centrifuge cycle. The concentration of the MXene dispersion was
measured by vacuum filtration of a known volume of solution and
measuring the mass of the resulting free-standing film. To increase
the concentration, the MXene dispersion was centrifuged at 9,000
rpm for 2 hours, the clear supernatant was decanted, and the
sediment was redispersed in a known volume of DI water. The new
concentration of the MXene dispersion, also called as-synthesized
MXene, was measured again before being used for dip-coating. Half
of the as-synthesized MXene dispersion was probe sonicated (Fisher
Scientific model 505 Sonic Dismembrator, 500 W) for 20 min under a
pulse setting (8 s on pulse and 2 s off pulse) at an amplitude of
50%. The MXene dispersion in a 50 mL glass bottle was inserted in
an ice bath to keep the dispersion cool during sonication.
[0125] Characterization:
[0126] The flake size distributions and the zeta potential
measurements of the MXene dispersions were conducted using dynamic
light scattering (DLS). Diluted MXene dispersion was transferred
into a polystyrene cuvette (Zetasizer Nano ZS, Malvern Instruments,
USA), and a total of five measurements from each sample were taken
for the DLS average. The weight of the yarn was measured using a
scale (Mettler Toledo, Columbus, Ohio) before and after dip-coating
to determine the MXene loading. Scanning electron microscopy (SEM)
images were taken on a Zeiss Supra 50 VP with an accelerating
voltage of 3 kV to observe the MXene coating on the individual
fibers and the yarn surface. Yarn cross-sections were obtained by
submerging the yarn in liquid nitrogen and then manually breaking
the frozen yarn. X-ray diffraction (XRD) was conducted to study the
structure of the precursor Ti.sub.3AlC.sub.2 MAX, Ti.sub.3C.sub.2
MXene film, pristine cotton and MXene-coated cotton yarn. A Rigaku
Miniflex II--Gen. 6 (Rigaku Co. Ltd. USA) with Cu K.sub..alpha.
(.lamda.=0.1542 nm) source and graphite K.sub..beta. filter was
used for measurements and the spectra were acquired at 40 kV
voltage and 15 mA current for 2-theta values from 2 to 65 degrees.
AFM measurements were done using a NX-10 (Park Systems, Korea) in a
standard tapping mode in air. The drive frequency was 272 kHz. The
image was collected at 15 by 15 .mu.m scan size at a scan rate of
0.3 Hz. AFM samples were prepared by spin-coated MXene solutions on
Si/SiO.sub.2 (300 nm) at 3000 rpm for 60 s. The substrates were
then dried at 7000 rpm for 15 s. X-ray photoelectron spectroscopy
(XPS) was conducted using PHI VersaProbe 5,000 instrument (Physical
Electronics, USA) with a 200 .mu.m and 50 W monochromatic
Al-K.sub..alpha. (1486.6 eV) X-ray source. Charge neutralization
was accomplished through a dual beam setup using low energy
Ar.sup.+ ions and low energy electrons at 1 eV/200 .mu.A.
Sputtering on 2.times.2 mm.sup.2 area was conducted using
Ar.sup.+-ion source at 4 kV accelerating voltage and 5 mA cm.sup.-2
current density for up to 3 minutes. High-resolution Ti-2p region
spectra were collected using pass energy and energy resolution of
23.5 eV and 0.05 eV, respectively. No binding energy scale
correction was applied as the samples were conducting, charge
neutralization was adequate, and no irregular shifts in the spectra
were observed even after sputtering. Quantification and peak
fitting were conducted using CasaXPS V2.3.19. Mixed
Gaussian-Lorentzian, GL(30), peak shape was used for oxygen related
moieties (TiO.sub.2), and asymmetric Lorentzian, LA(2,4,6), was
used for metal related moieties (Ti--C, Ti--O, Ti--F).
[0127] The electrical resistance of the MXene-coated yarns was
measured using a two-point probe with Keysight 2400 multimeter by
repeating the test on at least ten different positions. The
diameter of the yarns was measured using an Olympus PMG 3 (Olympus,
Center Valley, Pa.) optical microscope from an average of ten
different locations along the yarn length. Conductivity (a) was
calculated by .sigma.=I/RA.sub.C, where l, R, and Ac are the
length, resistance, and the cross-sectional area of the yarn,
respectively. The mechanical properties of the MXene-coated
cellulose-based yarns were analyzed using a DHR-3 (TA Instruments,
DE) rheometer with a 50 N load cell and crosshead speed of 1.5
mm/min. Samples were prepared by attaching the yarn vertically onto
a rectangular paper frame with 25 mm gauge length. After mounting
the frame on the grips, the paper was cut in the middle and the
yarn was stretched at a strain rate of 0.001/s (6%/min) until
failure.
[0128] Knitting:
[0129] The MXene-coated cellulose-based yarns were knitted using a
15-gauge, SWG041N Shima Seiki computerized knitting machine. The
Apex-3 Design software was used to program knitted devices and
samples. Rectangular swatches were knitted using interlock and
half-gauge stitch patterns. The pressure sensor button was fully
knitted from start to finish using MXene-coated bamboo yarns (0.6
mg/cm MXene loading) as the electrode material. The sensor consists
of two electrodes that were independently knitted on two separate
planes (front surface and back surface). Two individual feeders,
each carrying a MXene-coated bamboo yarn, were used to
simultaneously knit the two independent fabric electrodes with
reflective symmetry. A key consideration was to avoid contact
between the two electrodes to prevent short circuiting. This was
achieved by carefully designing the knitting program. After
knitting of active material was completed, the machine signalled a
programmed stop. The dielectric layer (nitrile rubber) was then
carefully placed between the fabric electrodes and the pocket was
closed by knitting a commercial viscose yarn on the subsequent row,
securing the dielectric layer.
[0130] Washability:
[0131] MXene-coated cotton yarns were washed with 1 mg/mL
Synthrapol solution, where they were loosely secured onto a mesh to
prevent tangling during the washing process. Synthrapol is a mild
detergent commonly used in yarn and fabric dyeing, which
facilitates removing loose dye particles from the substrate. The
MXene-coated cotton yarns fixed to the mesh were placed into a vial
with the Synthrapol and stirred at 500 rpm, where the mesh was free
to move during stirring. Two sets of 100 cm long MXene-coated
cotton yarns were washed for 20 washing cycles (60 min stirring for
each cycle at 500 rpm) at 30.degree. C. Then, the same yarns
(washed at 30.degree. C. for 20 washing cycles) were further washed
5 more cycles at each listed temperature consecutively: 40.degree.
C., 50.degree. C., 60.degree. C., 70.degree. C., and 80.degree. C.
As a result, the yarns were washed 45 washing cycles in total. For
each set of yarns, the MXene loading and the linear resistance
along ten .about.1 cm long yarn segments were measured and
compared. Next, the yarns were rinsed with deionized water (DI) and
air dried at room temperature for at least 6 h and then dried in a
vacuum desiccator for 4 h prior to measuring the mass loss and
linear resistance.
[0132] Fabrication of Yarn Electrodes:
[0133] The electrochemical properties of the MXene-coated cotton
yarns were studied in a three-electrode configuration. The counter
and the reference electrodes were graphite rod and Ag/AgCl (3 M
KCl), respectively and 1 M H.sub.2SO.sub.4 was used as the
electrolyte. The working electrode was prepared by attaching a
.about.25-30 mm long MXene-coated cotton yarn (2.5 mg/cm of MXene
loading) to the end of a fine silver wire using conductive silver
paste. The connection and the silver wire were sealed using epoxy
glue to avoid contact of silver paste with the electrolyte.
[0134] Fabrication of Yarn Supercapacitor Devices (YSC):
[0135] For the yarn supercapacitor (YSC) device,
PVA--H.sub.2SO.sub.4 gel electrolyte was prepared by dissolving 3 g
of PVA powder (Sigma-Aldrich, MW=89,000-98,000) in 30 mL of water
at 85.degree. C. under vigorous stirring. 3 g of sulfuric acid (98
wt. %, H.sub.2SO.sub.4, Fisher Chemical) was added to the PVA
solution after it cooled down to room temperature and a homogenous
gel was achieved. For preparation of YSCs, MXene-coated cotton
yarns (length of each yarn .about.60 mm) were immersed in the
PVA--H.sub.2SO.sub.4 gel electrolyte for .about.10 mins and dried
in air overnight. The YSC device was prepared in parallel
configuration by placing two MXene-coated cotton yarn electrodes
next to each other and coating twice with PVA--H.sub.2SO.sub.4 gel
electrolyte to ensure a complete coating.
[0136] Characterization of Yarn Electrodes and YSC:
[0137] Cyclic voltammetry (CV), galvanostatic charge-discharge
(GCD), and electrochemical impedance spectroscopy (EIS) were
performed using an electrochemical workstation (VMP 3, BioLogic,
France) at room temperature. Yarn electrodes and devices were
pre-cycled using CV at 100 mV/s for 20 cycles prior to recording
the electrochemical data. The current density values extracted in
the CV and GCD curves were normalized to the length of the yarn
electrode. For the three-electrode setup, CV and GCD curves were
recorded at a potential window of 0.25 to -0.55 V (vs. Ag/AgCl) at
the scan rates ranging from 2 to 100 mV/s and at the specific
current per length of 2 to 24 mA/cm, respectively. For the
two-electrode setup, CV and GCD curves were recorded in a voltage
window of 0 to 0.6 V at the scan rates ranging from 2 to 100 mV/s
and at the specific current per length of 0.5 to 12 mA/cm. The
electrochemical impedance spectroscopy (EIS) was performed at
open-circuit potential within a frequency range from 1 mHz to 1 MHz
at an alternating-current voltage with 10 mV amplitude. Cycling
stability was measured by repeating the GCD test for 10,000 cycles
at a current density of 30 mA/cm and 5 mA/cm for three-electrode
and two-electrode setups, respectively.
[0138] The capacitance was calculated by integrating the discharge
portion of the CV data using the following equation:
C D = .intg. 0 t .times. idV v .times. .times. .DELTA. .times.
.times. V ( 1 ) ##EQU00001##
[0139] where i is the instantaneous current at the potential of V,
.nu. is the scan rate (V/s), and .DELTA.V is the potential/voltage
window (V). The numerator of the equation is the integral of the
discharge portion of the CV curve. The length (C.sub.L, mF/cm),
areal (C.sub.A, mF/cm.sup.2), volumetric (C.sub.V, F/cm.sup.3), and
linear density (C.sub.Tex, mF/Tex) specific capacitances of the
electrode were obtained by normalizing the capacitance to the
length, outer surface area, volume, and the linear density (Tex) of
the yarn electrode respectively (for three-electrode
configuration). The specific capacitances of the supercapacitor
device were calculated by normalizing the capacitance to the length
of the whole device, total area, total volume, and the total linear
density of the device, respectively (including both electrodes with
same length).
[0140] The outer surface area (A) and volume (V) of the yarn
electrode were calculated using the following equations:
Area:A=2.pi.rl, (2)
Volume:V=.pi.r.sup.2l, (3)
where l denotes the length of the electrode, r is the radius of the
yarn electrode. The capacitance retention (C.sub.Ret) of the
electrode and the YSC device were calculated from the specific
capacitance in the first cycle (C.sub.1) and the specific
capacitance after the cycle number i, using the following
equation:
C Ret = C i C 1 .times. 100 .times. % ( 4 ) ##EQU00002##
[0141] Characterization of the Pressure Sensor:
[0142] The pressure sensing properties of the knitted samples were
measured by real-time monitoring of the capacitance response during
the cyclic compression-relaxation tests. Synchronized mechanical
and electrical (electromechanical) data were collected using an
Instron 3300 (Model 3365, Norwood, Mass.) with a 100 N load cell at
a crosshead speed of 5 mm/min and a multimeter (Model 34461A,
Keysight, Santa Rosa, Calif.). Dimensions of each electrode used
for the electromechanical test were 60 mm.times.65 mm in total area
and 16 mm.times.26 mm in active area with a dielectric thickness of
.about.72 .mu.m and a total sensor thickness of .about.2.5 mm. The
active area of the pressure sensor was knitted using MXene-coated
bamboo yarns with 0.6 mg/cm MXene loading. The surrounding textile
was knitted using a commercial viscose yarn (70 Tex). Relative
capacitance change (.DELTA.C/C.sub.0) was calculated, which
represents capacitance (C) at each point normalized in respect to
the initial capacitance (C.sub.0).
[0143] Additional Disclosure
[0144] Knittable and Washable Multifunctional MXene-Coated
Cellulose Yarns
[0145] The XRD pattern of the Ti.sub.3C.sub.2 MXene film is
characterized by the (00l) family of planes, defined by the
interlayer spacing, where l=2, 4, 6, 8, 10, . . . . These
reflections correspond to the out-of-plane stacking of single layer
MXene flakes. The asterisk (*) indicates a second layer of
intercalated water within the structure. XRD pattern of pristine
cotton yarn demonstrates the cellulose peak at
2.theta.=23.2.degree. corresponds to (002) reflection..sup.[59]
Because of the relatively good in-plane alignment of flakes in the
vacuum filtered Ti.sub.3C.sub.2 film, peaks corresponding to the
basal direction are broad, but well resolved. However, in the
MXene-coated cotton yarn, the flakes are randomly oriented hence
new peaks appear, including those for vertically aligned flakes.
According to Ghidiu et al. the peaks at 2.theta.=61.degree. and
2.theta.=35.degree./37.degree. correspond to (110) and (011)/(010)
reflections, respectively, while the broad peak at
2.theta.=41.5.degree. corresponds to the (016) Ti.sub.3C.sub.2
reflection..sup.[60] In general, the high intensity between
3.degree. and 10.degree. indicates that MXene is homogenously
dispersed throughout the cotton material as there is a wide
distribution of the interlayer spacings.
TABLE-US-00001 TABLE 1 Summary of the high-resolution Ti2p XPS
region fittings of unwashed and washed MXene-coated cotton yarns
before sputtering and after 3 min sputtering, shown in FIG. 4b,
FIG. 10c, and FIG. 4c, respectively. Unwashed Washed No Sputtering
Washed 3 min Sputtering Name Pos. FWHM % Area Pos. FWHM % Area Pos.
FWHM % Area Ti(1+) 3/2 454.96 0.69 7.56 454.96 0.64 4.58 454.79
0.58 3.10 Ti(1+) 1/2 461.16 1.39 3.78 461.16 1.41 2.29 460.99 1.32
1.55 Ti(2+) 3/2 455.75 1.51 36.42 455.86 1.52 26.79 455.50 1.74
31.48 Ti(2+) 1/2 461.55 2.10 18.20 461.66 2.09 13.39 461.30 1.78
15.73 Ti(3+) 3/2 457.20 1.86 17.86 457.23 1.17 6.25 457.38 1.78
15.73 Ti(3+) 1/2 462.90 2.50 8.92 462.93 2.50 3.12 463.08 1.98 7.86
TiO.sub.2 3/2 459.20 1.50 4.85 459.30 1.45 29.07 459.30 2.00 16.38
TiO.sub.2 1/2 464.90 2.50 2.42 465.00 2.50 14.52 465.00 2.50
8.19
EXAMPLE EMBODIMENTS
[0146] The following embodiments are exemplary only and do not
serve to limit the scope of the present disclosure or of the
appended claims.
[0147] Embodiment 1. A conductive fiber, comprising: a substrate
fiber, the substrate fiber defining an outer surface coated with a
first plurality of MXene particulates.
[0148] Embodiment 2. The conductive fiber of Embodiment 1, wherein
the substrate fiber comprises a naturally occurring material.
Cotton, linen, silk, wool, cashmere, hemp, jute, angora, and blends
are examples of natural fibers; cotton, linen, and silk are
considered especially suitable.
[0149] Embodiment 3. The conductive fiber of Embodiment 1, wherein
the substrate fiber comprises a synthetic material. Nylon,
polyester, acrylic, aramid, modal, carbon, glass, rayon, elastomer
fibers (e.g., polyurethane, olefin fibers such as polypropylene and
polyethylene, and blends) are all exemplary synthetic fibers.
Nylon, polyester, carbon, and glass fibers are considered
especially suitable.
[0150] Embodiment 4. The conductive fiber of Embodiment 1, wherein
the first plurality of MXene particulates has an average particle
size in the range of from about 100 to about 1000 nm, e.g., from
about 100 to about 1000 nm, from about 200 to about 900 nm, from
about 300 to about 800 nm, from about 400 to about 700 nm, or even
from about 500 to about 600 nm. The average particle size of the
MXenes can be selected such that it is smaller than the diameter of
the fibers onto which the MXenes are coated. As an example, the
MXene particles used with cotton fibers having an average diameter
of 20 micron can be smaller than the fibers with an average
diameter of 50 micron.
[0151] As another example, in the case of cotton, bamboo, and linen
fibers, the average flake size was around 300 nm to coat the
fibers, which is the most likely size range for MXene particles to
coat fibers in the commercial embodiment.
[0152] Embodiment 5. The conductive fiber of any one of Embodiments
1-4, wherein the first plurality of MXene particulates comprises
two different MXene materials. The different MXene materials can
differ in terms of their size, in terms of their composition, or in
terms of their size and composition.
[0153] Embodiment 6. The conductive fiber of any one of Embodiments
1-5, wherein the first plurality of MXene particulates defines a
unimodal particle size distribution.
[0154] Embodiment 7. The conductive fiber of any one of Embodiments
1-5, wherein the first plurality of MXene particulates defines a
multimodal particle size distribution.
[0155] Embodiment 8. The conductive fiber of any one of Embodiments
1-5, wherein the first plurality of MXene particulates are attached
to the substrate fiber by electrostatic interaction. In the case of
synthetic yarns, the fiber surface can be functionalized using
plasma cleaner or chemical etchants to ensure the MXene adhesion to
the fiber surface. For natural fibers, there is no need for any
processing prior to the coating, it is purely due to electrostatic
interactions.
[0156] Embodiment 9. A yarn, comprising: a plurality of conductive
fibers according to any one of Embodiments 1-8. It should be
understood that a yarn can comprise fibers that differ from one
another in size, composition, or both. A yarn can, for example,
comprise natural fibers and synthetic fibers.
[0157] Embodiment 10. The yarn of Embodiment 9, the yarn defining
an outer surface coated with a second plurality of MXene
particulates.
[0158] Embodiment 11. The yarn of Embodiment 10, wherein the second
plurality of MXene particulates has an average particle size in the
range of from about 500 to about 15,000 nm, e.g., from about 700 to
about 12,000 nm, or from about 1,000 to about 10,000 nm, or from
about 1,500 to about 7,500 nm, or even from about 2,500 to about
6,500 nm. MXene particulates (which can be, e.g., flakes in
configuration) can have an average particle size of from about 1000
to about 3000 nm.
[0159] Embodiment 12. The yarn of any one of Embodiments 9-11,
wherein the second plurality of MXene particulates comprises two
different MXene materials. The MXene materials can differ in terms
of size, in terms of composition, or both.
[0160] Embodiment 13. The yarn of any one of Embodiments 9-12,
wherein the second plurality of MXene particulates defines a
unimodal particle size distribution.
[0161] Embodiment 14. The yarn of any one of Embodiments 9-12,
wherein the first plurality of MXene particulates defines a
multimodal particle size distribution.
[0162] Embodiment 15. The yarn of any one of Embodiments 9-14,
wherein the second plurality of MXene particulates are attached to
the outer surface of the yarn by electrostatic interaction.
[0163] Embodiment 16. The yarn of Embodiment 9, wherein the yarn is
characterized as having a MXene loading of from about 0.1 to about
2.0 mg/cm.
[0164] MXene loading at the level of fibers can depend on the
number of dips used to coat the fibers. (Single- or multi-dip
processes can be used.) The loading can depend on the requirements
of the application. For example, sensor applications may not in all
cases require highly conductive yarns, and can thus MXene loading
of 0.6-1.0 mg/cm would be sufficient. On the other hand, for
supercapacitor applications, capacitance is directly correlated to
MXene loading, so higher the MXene loading (e.g. >2.0 mg/cm),
the higher the specific capacitance of the device.
[0165] Embodiment 17. The yarn of Embodiment 9, wherein the yarn is
characterized as having a MXene mass loading of from about 10 to
about 75 wt %, or from about 15 to about 70 wt %, or from about 20
to about 65 wt %, or from about 30 to about 55 wt %, or even about
40 wt %.
[0166] Embodiment 18. The yarn of Embodiment 9, wherein the yarn is
characterized as having a conductivity of from about 30 to about
150 S/cm.
[0167] Embodiment 19. The yarn of any one of Embodiments 10-15,
wherein the yarn is characterized as having a MXene loading of from
about 2.0 to about 3.0 mg/cm.
[0168] Embodiment 20. The yarn of any one of Embodiments 10-15 or
19, wherein the yarn is characterized as having a MXene mass
loading of from about 75 to about 85 wt %.
[0169] Embodiment 21. The yarn of any one of Embodiments 10-15 or
19, wherein the yarn is characterized as having a conductivity of
from about 200 to about 440 S/cm.
[0170] Embodiment 22. A yarn, comprising: a plurality of conductive
fibers, the yarn defining an outer surface coated with a plurality
of MXene particulates.
[0171] Embodiment 23. A method, comprising: forming a fiber
according to any one of Embodiments 1-8.
[0172] Embodiment 24. A method, comprising: forming a yarn
according to any one of Embodiments 9-22.
[0173] Embodiment 25. A knitted, woven, or non-woven fabric
comprising a fiber according to any one of Embodiments 1-8, the
knitted, woven, or non-woven fabric optionally being characterized
as having a MXene loading level that changes by less than about 1%
following washing for 20 h at 30 deg. C., 5 h at 40 deg. C., 5 h at
50 deg. C., 5 h at 60 deg. C., 5 h at 70 deg. C., and 5 h at 80
deg. C.
[0174] Embodiment 26. A knitted, woven, or non-woven fabric
comprising a yarn according to any one of Embodiments 9-22, the
knitted, woven, or non-woven fabric optionally being characterized
as having a MXene loading level that changes by less than about 1%
following washing for 20 h at 30 deg. C., 5 h at 40 deg. C., 5 h at
50 deg. C., 5 h at 60 deg. C., 5 h at 70 deg. C., and 5 h at 80
deg. C.).
[0175] Embodiment 27. A method, comprising: coating a plurality of
substrate fibers with a first plurality of MXene particulates so as
to form coated substrate fibers.
[0176] Embodiment 28. The method of Embodiment 27, wherein coating
the plurality of substrate fibers comprises dip coating, inking,
spraying, or any combination thereof. One can perform a single- or
multiple-dip process. One can also apply a MXene ink to fibers or
to yarn, e.g., by brushing, jetting, and other methods of
application.
[0177] Embodiment 29. The method of any one of Embodiments 27-28,
further comprising forming a yarn from the plurality of coated
substrate fibers.
[0178] Embodiment 30. The method of Embodiment 29, further
comprising coating the yarn with a second plurality of MXene
particulates.
[0179] Embodiment 31. The method of Embodiment 30, wherein coating
the yarn comprises dip coating, inking, spraying, or any
combination thereof.
[0180] Embodiment 32. A device, the device comprising a fiber
according to any one of Embodiments 1-8 or a yarn according to any
one of Embodiments 9-22.
[0181] Embodiment 33. The device of Embodiment 32, wherein the
device comprises a capacitor, an energy harvesting device, an
antenna, a heater, an electromagnetic interference shield, or any
combination thereof.
[0182] Embodiment 34. The device of Embodiment 32, wherein the
device comprises an electrolyte contacting a fiber according to any
one of Embodiments 1-8 or a yarn according to any one of
Embodiments 9-22.
[0183] Embodiment 35. A pressure sensor, comprising: a first
electrode; a second electrode; and a dielectric material disposed
so as to place the first electrode into electrical isolation from
the second electrode, at least one of the first electrode and the
second electrode comprising (a) a substrate fiber, the substrate
fiber defining an outer surface coated with a first plurality of
MXene particulates, (b) a yarn comprising a plurality of coating
fibers, each coating fiber comprising a substrate fiber defining an
outer surface coated with a first plurality of MXene particulates,
(c) a yarn comprising a plurality of coating fibers, each coating
fiber comprising a substrate fiber defining an outer surface coated
with a first plurality of MXene particulates and the yarn defining
an outer surface coated with a second plurality of MXene
particulates, or (d) a yarn comprising a plurality of fibers, the
yarn defining an outer surface coated with a second plurality of
MXene particulates.
[0184] The disclosed pressure sensors can be used in a variety of
devices, e.g., touchscreen sensors, switches, capacitors, and the
like. Touchscreen applications are especially suitable for the
disclosed devices.
[0185] Embodiment 36. The pressure sensor of Embodiment 35, wherein
at least one of the first electrode and the second electrode is
characterized as being a woven fabric, a knitted fabric, or a
nonwoven fabric.
[0186] Embodiment 37. The pressure sensor of any one of Embodiments
35-36, wherein a substrate fiber comprises a synthetic material.
Suitable synthetic materials include, e.g., nylon, polyester,
acrylic, aramid, modal, carbon, glass, rayon, elastomer fibers such
as polyurethane, olefin fibers such as polypropylene and
polyethylene, and blends thereof. Nylon, polyester, carbon, and
glass fibers are especially suitable.
[0187] A substrate fiber can also comprise a natural fiber.
Suitable natural fibers include, e.g., cotton, linen, silk, wool,
cashmere, hemp, jute, angora, and blends thereof. Cotton, linen,
and silk are especially suitable.
[0188] Embodiment 38. The pressure sensor of Embodiment 37, wherein
the first plurality of MXene particulates has an average particle
size in the range of from about 100 to about 1000 nm, e.g., from
about 200 to about 800 nm, from about 300 to about 700 nm, or from
about 400 to about 600 nm.
[0189] MXene particulate size can depend on the average fiber
diameter that will be infiltrated with MXene. For example, the
MXene particulates for fibers with an average diameter of 20
microns can be smaller than MXene particulates used with fibers
having an average diameter of 50 micron.
[0190] In case of cotton, bamboo, and linen fibers, MXene particles
can be around 300 nm in size, which size can coat fibers.
[0191] Embodiment 39. The pressure sensor of any one of Embodiments
35-38, wherein the first plurality of MXene particulates comprises
two different MXene materials. The two MXene materials can differ
in size, in composition, or both.
[0192] Embodiment 40. The pressure sensor of any one of Embodiments
35-39, wherein the first plurality of MXene particulates defines a
unimodal particle size distribution.
[0193] Embodiment 41. The pressure sensor of any one of Embodiments
35-40, wherein the first plurality of MXene particulates defines a
multimodal particle size distribution.
[0194] Embodiment 42. The pressure sensor of any one of Embodiments
35-41, wherein the first plurality of MXene particulates are
attached to the substrate fiber by electrostatic interaction. In
some embodiments, a fiber surface can be functionalized using
plasma cleaner or chemical etchants to enhance MXene adhesion to
the fiber surface. For natural fibers, it is not necessary to
perform processing, as MXene particulates can secure to fibers due
to electrostatic interactions.
[0195] Embodiment 43. The pressure sensor yarn of any one of
Embodiment 35-42, wherein the second plurality of MXene
particulates has an average particle size in the range of from
about 500 to about 1500 nm, e.g., from about 500 to about 1500 nm,
or from about 700 to about 1300 nm, or from about 900 to about
1100, or even about 1000 nm.
[0196] Embodiment 44. The pressure sensor of any one of Embodiments
35-43, wherein the second plurality of MXene particulates comprises
two different MXene materials.
[0197] Embodiment 45. The pressure sensor of any one of Embodiments
35-44, wherein the second plurality of MXene particulates defines a
unimodal particle size distribution.
[0198] Embodiment 46. The pressure sensor of any one of Embodiments
35-45, wherein the second plurality of MXene particulates are
attached to the outer surface of the yarn by electrostatic
interaction.
[0199] Embodiment 47. The pressure sensor of any one of Embodiments
35-46, wherein the yarn is characterized as having a MXene loading
of from about 0.1 to about 2.0 mg/cm, or from about 0.3 to about
1.7 mg/cm, or even from about 0.7 to about 1.2 mg/cm.
[0200] The MXene loading can depend on the method by which the
MXene is coated onto the fibers/yarn. As an example, MXene loading
can depend on the number of dips in a dip coating process; the
loading can be increased as the number of dips increases. A MXene
loading of 0.6-1.2 mg/cm can be used, in some embodiments.
[0201] Embodiment 48. The pressure sensor of any one of Embodiments
35-47, wherein the yarn is characterized as having a MXene mass
loading of from about 10 to about 75 wt %, or from about 15 to
about 70 wt %, or from about 20 to about 65 wt %, or from about 25
to about 55 wt %, or from about 30 to about 45 wt %, or even about
40 wt %.
[0202] Embodiment 49. The pressure sensor of any one of Embodiments
35-48, wherein the yarn is characterized as having an electrical
conductivity of from about 30 to about 150 S/cm, or from about 50
to about 120 S/cm, or from 70 to about 110 S/cm, or even from about
90 to about 100 S/cm. The conductivity of the yarns can depend on
MXene loading and yarn diameter. As the MXene loading increases and
the diameter of the yarn decreases, the overall electrical
conductivity of the yarn will be increased. Electrical conductivity
in the range of from about 80 to about 100 S/cm is considered
especially suitable.
[0203] Embodiment 50. The pressure sensor of any one of Embodiments
35-49, wherein the pressure sensor is characterized as having a
gauge factor of from about 0.1 to about 10, e.g., from about 0.1 to
about 10, from about 1 to about 9, from about 2 to about 8, from
about 3 to about 7, from about 4 to about 6, or even about 5.
[0204] Embodiment 51. A method, comprising operating a pressure
sensor according to any one of Embodiments 35-50.
[0205] Embodiment 52. A strain sensor, comprising: a sensor region,
the sensor region comprising (a) a substrate fiber, the substrate
fiber defining an outer surface coated with a first plurality of
MXene particulates, (b) a yarn comprising a plurality of coating
fibers, each coating fiber comprising a substrate fiber defining an
outer surface coated with a first plurality of MXene particulates,
(c) a yarn comprising a plurality of coating fibers, each coating
fiber comprising a substrate fiber defining an outer surface coated
with a first plurality of MXene particulates and the yarn defining
an outer surface coated with a second plurality of MXene
particulates; and or (d) a yarn comprising a plurality of fibers,
the yarn defining an outer surface coated with a second plurality
of MXene particulates, and a charge collector configured to monitor
a signal of the sensor region related to a strain experienced by
the panel.
[0206] Embodiment 53. The strain sensor of Embodiment 52, wherein
the sensor region is characterized as being a knitted fabric, a
woven fabric, or a nonwoven fabric.
[0207] Embodiment 54. A method, comprising operating a strain
sensor according to any one of Embodiments 52-53.
REFERENCES
[0208] D. Yu, K. Goh, H. Wang, L. Wei, W. Jiang, Q. Zhang, L. Dai,
Y. Chen, Nat. Nanotechnol. 2014, 9, 555. [0209] D. Yu, Q. Qian, L.
Wei, W. Jiang, K. Goh, J. Wei, J. Zhang, Y. Chen, Chem. Soc. Rev.
2015, 44, 647. [0210] K. Jost, G. Dion, Y. Gogotsi, J. Mater. Chem.
A 2014, 2, 10776. [0211] W. Weng, P. Chen, S. He, X. Sun, H. Peng,
Angew. Chem. Int. Ed. 2016, 55, 6140. [0212] Q. Xue, J. Sun, Y.
Huang, M. Zhu, Z. Pei, H. Li, Y. Wang, N. Li, H. Zhang, C. Zhi,
Small 2017, 13, 1701827. [0213] A. K. Yetisen, H. Qu, A. Manbachi,
H. Butt, M. R. Dokmeci, J. P. Hinestroza, M. Skorobogatiy, A.
Khademhosseini, S. H. Yun, ACS Nano 2016, 10, 3042. [0214] K. Jost,
D. Stenger, C. R. Perez, J. K. McDonough, K. Lian, Y. Gogotsi, G.
Dion, Energy Environ. Sci. 2013, 6, 2698. [0215] K. Jost, C. R.
Perez, J. K. McDonough, V. Presser, M. Heon, G. Dion, Y. Gogotsi,
Energy Environ. Sci. 2011, 4, 5060. [0216] M. Hu, Z. Li, G. Li, T.
Hu, C. Zhang, X. Wang, Adv. Mater. Technol. 2017, 2, 1700143.
[0217] J. Zhang, S. Seyedin, Z. Gu, W. Yang, X. Wang, J. M. Razal,
Nanoscale 2017, 9, 18604. [0218] X. Xiao, T. Li, P. Yang, Y. Gao,
H. Jin, W. Ni, W. Zhan, X. Zhang, Y. Cao, J. Zhong, L. Gong, W.-C.
Yen, W. Mai, J. Chen, K. Huo, Y.-L. Chueh, Z. L. Wang, J. Zhou, ACS
Nano 2012, 6, 9200. [0219] H. Yang, H. Xu, M. Li, L. Zhang, Y.
Huang, X. Hu, ACS Appl. Mater. Interfaces 2016, 8, 1774. [0220] V.
T. Le, H. Kim, A. Ghosh, J. Kim, J. Chang, Q. A. Vu, D. T. Pham,
J.-H. Lee, S.-W. Kim, Y. H. Lee, ACS Nano 2013, 7, 5940. [0221] K.
Jost, D. P. Durkin, L. M. Haverhals, E. K. Brown, M. Langenstein,
H. C. De Long, P. C. Trulove, Y. Gogotsi, G. Dion, Adv. Energy
Mater. 2015, 5, 1401286. [0222] M. Tebyetekerwa, I. Marriam, Z. Xu,
S. Yang, H. Zhang, F. Zabihi, R. Jose, S. Peng, M. Zhu, S.
Ramakrishna, Energy & Environmental Science 2019. [0223] R.
Jalili, J. M. Razal, P. C. Innis, G. G. Wallace, Adv. Funct. Mater.
2011, 21, 3363. [0224] J. Zhang, S. Seyedin, S. Qin, Z. Wang, S.
Moradi, F. Yang, P. A. Lynch, W. Yang, J. Liu, X. Wang, J. M.
Razal, Small 2019, 15, 1804732. [0225] J. Zhang, S. Seyedin, S.
Qin, P. A. Lynch, Z. Wang, W. Yang, X. Wang, Joselito M. Razal, J.
Mater. Chem. A 2019, 7, 6401. [0226] N. He, Q. Pan, Y. Liu, W. Gao,
ACS Appl. Mater. Interfaces 2017, 9, 24568. [0227] X. Zhao, B.
Zheng, T. Huang, C. Gao, Nanoscale 2015, 7, 9399. [0228] T. Xu, X.
Ding, Y. Liang, Y. Zhao, N. Chen, L. Qu, Nanoscale 2016, 8, 12113.
[0229] V. A. Davis, A. N. G. Parra-Vasquez, M. J. Green, P. K. Rai,
N. Behabtu, V. Prieto, R. D. Booker, J. Schmidt, E. Kesselman, W.
Zhou, H. Fan, W. W. Adams, R. H. Hauge, J. E. Fischer, Y. Cohen, Y.
Talmon, R. E. Smalley, M. Pasquali, Nat. Nanotechnol. 2009, 4, 830.
[0230] N. Behabtu, C. C. Young, D. E. Tsentalovich, O. Kleinerman,
X. Wang, A. W. K. Ma, E. A. Bengio, R. F. ter Waarbeek, J. J. de
Jong, R. E. Hoogerwerf, S. B. Fairchild, J. B. Ferguson, B.
Maruyama, J. Kono, Y. Talmon, Y. Cohen, M. J. Otto, M. Pasquali,
Science 2013, 339, 182. [0231] Q. Meng, H. Wu, Y. Meng, K. Xie, Z.
Wei, Z. Guo, Adv. Mater. 2014, 26, 4100. [0232] M.-Q. Zhao, C. E.
Ren, Z. Ling, M. R. Lukatskaya, C. Zhang, K. L. Van Aken, M. W.
Barsoum, Y. Gogotsi, Adv. Mater. 2015, 27, 339. [0233] S. Seyedin,
E. R. S. Yanza, Joselito M. Razal, J. Mater. Chem. A 2017, 5,
24076. [0234] S. Seyedin, J. M. Razal, P. C. Innis, A.
Jeiranikhameneh, S. Beirne, G. G. Wallace, ACS Appl. Mater.
Interfaces 2015, 7, 21150. [0235] T. Chen, L. Qiu, Z. Yang, Z. Cai,
J. Ren, H. Li, H. Lin, X. Sun, H. Peng, Angew. Chem. Int. Ed. 2012,
51, 11977. [0236] Z. Wang, S. Qin, S. Seyedin, J. Zhang, J. Wang,
A. Levitt, N. Li, C. Haines, R. Ovalle-Robles, W. Lei, Y. Gogotsi,
R. H. Baughman, J. M. Razal, Small 2018, 14, 1802225. [0237] M. D.
Lima, S. Fang, X. Lepro, C. Lewis, R. Ovalle-Robles, J.
Carretero-Gonzalez, E. Castillo-Martinez, M. E. Kozlov, J. Oh, N.
Rawat, C. S. Haines, M. H. Hague, V. Aare, S. Stoughton, A. A.
Zakhidov, R. H. Baughman, Science 2011, 331, 51. [0238] C. Zhang,
B. Anasori, A. Seral-Ascaso, S.-H. Park, N. McEvoy, A. Shmeliov, G.
S. Duesberg, J. N. Coleman, Y. Gogotsi, V. Nicolosi, Adv. Mater.
2017, 29, 1702678. [0239] M. R. Lukatskaya, S. Kota, Z. Lin, M.-Q.
Zhao, N. Shpigel, M. D. Levi, J. Halim, P.-L. Taberna, M. W.
Barsoum, P. Simon, Y. Gogotsi, Nat. Energy 2017, 2, 17105. [0240]
M. Alhabeb, K. Maleski, B. Anasori, P. Lelyukh, L. Clark, S. Sin,
Y. Gogotsi, Chem. Mater. 2017, 29, 7633. [0241] M. R. Lukatskaya,
O. Mashtalir, C. E. Ren, Y. Dall'Agnese, P. Rozier, P. L. Taberna,
M. Naguib, P. Simon, M. W. Barsoum, Y. Gogotsi, Science 2013, 341,
1502. [0242] Z. Ling, C. E. Ren, M.-Q. Zhao, J. Yang, J. M.
Giammarco, J. Qiu, M. W. Barsoum, Y. Gogotsi, Proc. Natl. Acad.
Sci. 2014,111, 16676. [0243] M. D. Levi, M. R. Lukatskaya, S.
Sigalov, M. Beidaghi, N. Shpigel, L. Daikhin, D. Aurbach, M. W.
Barsoum, Y. Gogotsi, Adv. Energy Mater. 2015, 5, 1400815. [0244] M.
R. Lukatskaya, S.-M. Bak, X. Yu, X.-Q. Yang, M. W. Barsoum, Y.
Gogotsi, Adv. Energy Mater. 2015, 5, 1500589. [0245] H. Lin, X.
Wang, L. Yu, Y. Chen, J. Shi, Nano Lett. 2017, 17, 384. [0246] F.
Meng, M. Seredych, C. Chen, V. Gura, S. Mikhalovsky, S. Sandeman,
G. Ingavle, T. Ozulumba, L. Miao, B. Anasori, Y. Gogotsi, ACS Nano
2018, 12,10518. [0247] K. Maleski, C. E. Ren, M.-Q. Zhao, B.
Anasori, Y. Gogotsi, ACS Appl. Mater. Interfaces 2018, 10,
24491-24498. [0248] V. S. Smentkowski, Prog. Surf. Sci. 2000, 64,
1. [0249] T. Habib, X. Zhao, S. A. Shah, Y. Chen, W. Sun, H. An, J.
L. Lutkenhaus, M. Radovic, M. J. Green, npj 2D Materials and
Applications 2019, 3, 8. [0250] Y. Chae, S. J. Kim, S.-Y. Cho, J.
Choi, K. Maleski, B.-J. Lee, H.-T. Jung, Y. Gogotsi, Y. Lee, C. W.
Ahn, Nanoscale 2019, 11, 8387-8393. [0251] C. J. Zhang, S. Pinilla,
N. McEvoy, C. P. Cullen, B. Anasori, E. Long, S.-H. Park, A.
Seral-Ascaso, A. Shmeliov, D. Krishnan, C. Morant, X. Liu, G. S.
Duesberg, Y. Gogotsi, V. Nicolosi, Chem. Mater. 2017, 29,
4848-4856. [0252] G.-M. Weng, J. Li, M. Alhabeb, C. Karpovich, H.
Wang, J. Lipton, K. Maleski, J. Kong, E. Shaulsky, M. Elimelech, Y.
Gogotsi, A. D. Taylor, Adv. Funct. Mater. 2018, 28, 1803360. [0253]
D. Xiong, X. Li, Z. Bai, S. Lu, Small 2018, 14, 1703419. [0254] M.
Ghidiu, M. R. Lukatskaya, M.-Q. Zhao, Y. Gogotsi, M. W. Barsoum,
Nature 2014, 516, 78. [0255] M. Beidaghi, Y. Gogotsi, Energy
Environ. Sci. 2014, 7, 867. [0256] M. D. Stoller, R. S. Ruoff,
Energy Environ. Sci. 2010, 3, 1294. [0257] A. W. Bayes, J. Text.
Inst. Proc. 1957, 48, 255. [0258] L. Liu, Y. Yu, C. Yan, K. Li, Z.
Zheng, Nat. Commun. 2015, 6, 7260. [0259] N. Liu, W. Ma, J. Tao, X.
Zhang, J. Su, L. Li, C. Yang, Y. Gao, D. Golberg, Y. Bando, Adv.
Mater. 2013, 25, 4925. [0260] C. Jin, H.-T. Wang, Y.-N. Liu, X.-H.
Kang, P. Liu, J.-N. Zhang, L.-N. Jin, S.-W. Bian, Q. Zhu,
Electrochim. Acta 2018, 270, 205. [0261] Y.-Y. Peng, B. Akuzum, N.
Kurra, M.-Q. Zhao, M. Alhabeb, B. Anasori, E. C. Kumbur, H. N.
Alshareef, M.-D. Ger, Y. Gogotsi, Energy Environ. Sci. 2016, 9,
2847. [0262] N. Kurra, B. Ahmed, Y. Gogotsi, H. N. Alshareef, Adv.
Energy Mater. 2016, 6, 1601372. [0263] X. Wang, T. S. Mathis, K.
Li, Z. Lin, L. Vlcek, T. Torita, N. C. Osti, C. Hatter, P.
Urbankowski, A. Sarycheva, M. Tyagi, E. Mamontov, P. Simon, Y.
Gogotsi, Nat. Energy 2019, 4, 241. [0264] J. Lee, H. Kwon, J. Seo,
S. Shin, J. H. Koo, C. Pang, S. Son, J. H. Kim, Y. H. Jang, D. E.
Kim, T. Lee, Adv. Mater. 2015, 27, 2433-2439. [0265] D. J. Lipomi,
M. Vosgueritchian, B. C. K. Tee, S. L. Hellstrom, J. A. Lee, C. H.
Fox, Z. Bao, Nat. Nanotechnol. 2011, 6, 788. [0266] Liu, L.; Yu,
Y.; Yan, C.; Li, K.; Zheng, Z., Wearable energy-dense and
power-dense supercapacitor yarns enabled by scalable
graphene-metallic textile composite electrodes. Nature
Communications 2015, 6, 7260.
[0267] Jost, K.; Durkin, D. P.; Haverhals, L. M.; Brown, E. K.;
Langenstein, M.; De Long, H. C.; Trulove, P. C.; Gogotsi, Y.; Dion,
G., Natural Fiber Welded Electrode Yarns for Knittable Textile
Supercapacitors. Advanced Energy Materials 2015, 5 (4), 1401286.
[0268] Wang, Z.; Qin, S.; Seyedin, S.; Zhang, J.; Wang, J.; Levitt,
A.; Li, N.; Haines, C.; Ovalle-Robles, R.; Lei, W.; Gogotsi, Y.;
Baughman, R. H.; Razal, J. M., High-Performance Biscrolled
MXene/Carbon Nanotube Yarn Supercapacitors. Small 2018, 14 (37),
1802225. [0269] Zhang, J.; Seyedin, S.; Gu, Z.; Yang, W.; Wang, X.;
Razal, J. M., MXene: a potential candidate for yarn
supercapacitors. Nanoscale 2017, 9 (47), 18604-18608. [0270] Hu,
M.; Li, Z.; Li, G.; Hu, T.; Zhang, C.; Wang, X., All-Solid-State
Flexible Fiber-Based MXene Supercapacitors. Advanced Materials
Technologies 2017, 2 (10), 1700143. [0271] Seyedin, S.; Yanza, E.
R. S.; Razal, Joselito M., Knittable energy storing fiber with high
volumetric performance made from predominantly MXene nanosheets.
Journal of Materials Chemistry A 2017, 5 (46), 24076-24082. [0272]
S. Park, J. O. Baker, M. E. Himmel, P. A. Parilla, D. K. Johnson,
Biotechnol. Biofuels 2010, 3, 10. [0273] M. Ghidiu, M. W. Barsoum,
J. Am. Ceram. Soc. 2017, 100, 5395. [0274] J. Halim, K. M. Cook, M.
Naguib, P. Eklund, Y. Gogotsi, J. Rosen, M. W. Barsoum, Appl. Surf.
Sci. 2016, 362, 406. [0275] I. Persson, L.-.ANG.. Naslund, J.
Halim, M. W. Barsoum, V. Darakchieva, J. Palisaitis, J. Rosen, P.
O. .ANG.. Persson, 2D Materials 2017, 5, 015002.
* * * * *