Omnidirectional Deformable Energy Textile for Human JointMovement Compatible Energy StorageJoonwon Lim, Dong Sung Choi, Gil Yong Lee, Ho Jin Lee, Suchithra Padmajan Sasikala, Kyung Eun Lee,Seok Hun Kang, and Sang Ouk Kim*

National Creative Research Initiative Center for Multi-Dimensional Directed Nanoscale Assembly, Department of Materials Scienceand Engineering, KAIST, Daejeon 34141, Republic of Korea

*S Supporting Information

ABSTRACT: Omnidirectional deformability is an unavoidable basic requirement for wearable devices to accommodate humandaily motion particularly at human joints. We demonstrate omnidirectionally bendable and stretchable textile-basedelectrochemical capacitor that retains high power performance under complex mechanical deformation. Judicious synergistichybrid structure of woven elastic polymer yarns with carbon nanotubes and conductive polymers offers reliable electrical andelectrochemical activity even under repeated cycles of severe complex deformation modes. The textile-based electrochemicalcapacitors exhibit omnidirectional stretchability with 93% of capacitance retention under repeated 50% omnidirectionalstretching condition while demonstrating excellent specific capacitance (412 mF cm−2) and cycle stability (>2000 stretch). Thewearable power source stably powers red LED under omnidirectional stretching that accompanies human elbow joint motion.

KEYWORDS: energy storage, supercapacitors, textile, wearable, carbon nanotubes

■ INTRODUCTIONResearch attention on wearable electronics is ever-increasingalong with the rapid advent of portable or patchable devices.1−7

The ideal prototype of wearable electronics should be bendable,twistable, and stretchable to accommodate our daily mechanicalmotions, while sustaining the device performance in theundeformed states.8,9 In the past decade, a significant amountof research effort has been devoted to the realization ofwearable devices, mainly focusing on the engineering of devicestructures. For instance, buckling of ultrathin inorganic activematerials stabilized on prestrained elastomeric substratessuccessfully realizes uniaxially or biaxially stretchable devi-ces.10−14 Fiber-shaped devices can offer high tolerance forcomplex mechanical deformation modes owing to the intrinsicone-dimensional geometry.15−24 Nonetheless, a significant issuestill remains unsolved for the realization of genuine wearablepower devices, that is, reliable high power performance evenunder complex omnidirectional deformation.In the realm of truly wearable devices, omnidirectional

deformability needs to be distinguished from simple bendabilityor uni/biaxial stretchability. While conventional stretchabilitytoward one or a few fixed directions can accommodate only alimited range of physical motions, omnidirectional deformabledevices ensure a distinctive degree of freedom for physical

movement and comfort. Indeed, practical wearable poweringdevices are expected to accommodate 50% of omnidirectionalstrains to tolerate the large deformation occurring particularlyat joints, such as knee, elbow, and knuckle.25 A sophisticatedstrategy is expected in the design of materials and/or the layoutof devices for the simultaneous attainment of omnidirectionaldeformability along with high conductivity and energy storage/supply capability.26 Moreover, development of systematic andstandardized analytical methodology for the evaluation ofomnidirectional deformability is urgently demanded to resolvethe ambiguity among previous relevant approaches.27,28

Textile integration of powering devices is considered apromising platform for upcoming wearable electronics.29−32

Textile platform offers certain inherent flexibility andstretchability arising from the distinct woven structures, evenwhen composed of inelastic rigid materials. Nonetheless, it isstill challenging to synchronize the contradictory goals of highstretchability and reliable electrical conductivity,33 which areindispensable requirements for wearable powering textiles asactive materials as well as current collectors. To date, most of

Received: October 2, 2017Accepted: November 6, 2017Published: November 7, 2017

Research Article

www.acsami.org

© 2017 American Chemical Society 41363 DOI: 10.1021/acsami.7b14981ACS Appl. Mater. Interfaces 2017, 9, 41363−41370

Cite This: ACS Appl. Mater. Interfaces 2017, 9, 41363-41370

the research on textile-based power sources has relied oninelastic textile platform.34−39 In a few rare attempts to employelastic yarns, the resultant devices have suffered frominsufficient cycle stability, commonly caused by the fractureor delamination of rigid active components from the elasticyarns, which deteriorate the electrical connectivity over devicearchitecture during multiple repeated deformation cycles.31,40,41

In this work, we present omnidirectionally deformabletextile-based electrochemical capacitors, capable of stablepower storage/supply under complex mechanical deformation.A straightforward reliable interfacial treatment method isdeveloped for the commercially available woven elastic polymeryarns based on the solution deposition of carbon nanotubes(CNTs) and the interfacial synthesis of conductive polymer(polyaniline, PANI) layers. Simple capacitor structuresconsisting of symmetric stacking of the hybrid textiles attainhighly stable reliable energy storage and supply under severecomplex deformation conditions along with ready adaptabilityto our typical clothes. We also propose a standardizedquantitative evaluation method for the omnidirectionalstretchability in the functional device structures as well as inthe materials level.

■ EXPERIMENTAL METHODSPreparation of CNT/Textile. Aqueous CNT ink was prepared by

dispersing MWCNTs with sodium dodecylbenzenesulfonate (SDBS)as surfactant. The mass ratio of CNTs to SDBS was 1 to 5 for aqueousCNT ink of various concentration. Tip sonication of 20 W was appliedto the CNT ink for 1 h, and the resultant CNT ink was centrifuged at8000 rpm for 1 h to remove nondispersed CNT clusters. Stretchable

textile made of polyurethane and polyester copolymer was immersedin the as-prepared CNTs ink for 10 min and then dried out on a hot-plate at 50 °C for 2 h. The CNT-coated stretchable textile (CNT/textile) was washed out with deionized water with vigorous shaking toremove unattached and agglomerated CNT particles on the textile.Subsequent washing with 2 M nitric acid was conducted to completelyremove SDBS surfactants adsorbed on the surface of CNTs. The sameprocess was repeated to increase the loading amount of CNT on thestretchable textile.

Preparation of PANI/CNT/Textile. 0.2 M aniline in 1 Mhydrochloric acid (HCl) aqueous solution (20 mL) was prepared forin situ polymerization of PANI. High purity ethanol (4 mL) was addedto the prepared aniline solution. CNT/textile was immersed in ethanolfor tens of seconds to improve wettability and then placed into thereaction solution containing aniline monomer for 3 h in ice bath. 0.1M ammonium persulfate (APS) in 1 M HCl (20 mL) solution wasslowly added drop by drop into the reaction bath. The degree of in situpolymerization of PANI was controlled by adjusting the reaction time.After polymerization reaction, the synthesized PANI/CNT/textile wasthoroughly washed with ethanol with vigorous shaking to removeundesired PANI particles on the surface of PANI/CNT/textile anddried out on the hot-plate at 50 °C for 2 h.

Measurement of Electrical Stability under Uniaxial Stretch-ing. Specimens were stretched by homemade stretching testequipment. Both ends of specimens were clipped by holders withplatinum foils for electrical contact for measuring electrical property.The magnitude of applied tensile strain was defined as followingformula: magnitude of applied tensile strain (%) = 100 × (L − L0)/L0,where L0 and L denote the length of specimen before and after appliedtensile strain, respectively. Electrical stability under uniaxial stretchingwas evaluated with the variation of electrical resistance, defined as R/R0, where R0 and R denote electrical resistance before and after appliedtensile strain, respectively.

Figure 1. Omnidirectional deformable energy textile preparation. (a) Synthetic procedure for PANI/CNT/textile composite structure. (b−d) SEMimages of CNT/textile composites. (e−g) SEM images of PANI/CNT/textile composites. Scale bars are 2 μm in (b, e), 200 nm in (c, f), and 10 μmin (d, g).

ACS Applied Materials & Interfaces Research Article

DOI: 10.1021/acsami.7b14981ACS Appl. Mater. Interfaces 2017, 9, 41363−41370

41364

Measurement of Electrical Stability under OmnidirectionalStretching. Omnidirectional stretchability was evaluated by inves-tigating the variation of R/R0 under omnidirectional stretching.Specimens were held by homemade stretching test equipment. Alledges of specimen were clipped by holders, and platinum foils areplaced at two sides facing each other for electrical contact formeasuring electrical property. Omnidirectional stretching wasgenerated by sphere shape strain loader pressing specimen. Thedegree of applied omnidirectional strains was controlled by adjustingvertical location of sphere loader. The magnitude of omnidirectionalstrains was defined with the identical formula with that of uniaxialstretching condition. L0 and L denote the sectional line length passingthrough a tangential point between specimen and sphere loader beforeand after omnidirectional stretching, respectively. Electrical stabilityunder omnidirectional stretching was evaluated with the variation ofelectrical resistance (Romni/R0).Material information and evaluation method for electrochemical

performance of supercapacitors are provided in the SupportingInformation.

■ RESULTS AND DISCUSSION

Omnidirectionally Deformable Energy Textile Prep-aration. Figure 1a illustrates our synthetic route. Highlystretchable textiles woven from elastic polyester−polyurethanecopolymer yarns were immersed in aqueous dispersion ofCNTs with amphiphilic surfactants (Figure S1). The

immersion condition was precisely optimized for a desireduniform and conformal coating quality (Figure 1b−d, FigureS2). Several repeated CNT coating cycles (typically five times)dramatically decrease the sheet resistance of textile down to 20Ω/□ (Figure S3). Subsequently, PANI conductive polymerlayer was grown from the entire surface of CNT/textile (Figure1e−g, Figures S4 and S5). Aniline monomers are sufficientlyabsorbed on the CNT coated textile surface before polymer-ization so that the following solution polymerization leads to aconformal coating of PANI layer (Figure S4).42,43 PANI formsdense surface layer and plugs the cavities among CNTs and thebase textile (Figure S5). The polyester−polyurethane textileused here possesses aromatic moieties that can share π−πinteraction with CNTs and PANI chains.44 Besides, −NH−functional groups of PANI may cause hydrogen bondings withthe CO groups of polyester−polyurethane textile toaccommodate reliable interfacial adhesion even under severecomplex deformation (Figure S6).45 The interfacial interactionsenhanced the mechanical property of the textile (Figure S7).

Energy Textile under Bending, Twisting, and UniaxialStretching. Any kind of complex mechanical deformation,including those at human skin or clothing, can be considered asa combination of bending, twisting, and stretching modes.Electrical conductivity of our conductive textiles was charac-

Figure 2. Electrical stability of PANI/CNT/textile and CNT/textile under diverse mechanical deformation modes. (a, b) Variation of electricalresistance for PANI/CNT/textile and CNT/textile under bending and twisting conditions; insets are optical images for bending and twisting test.(c) Variation of electrical resistance for PANI/CNT/textile and CNT/textile under tensile stretching. X, Y, and XY indicate stretching direction asindicated in part d. (d) SEM images of textiles (black edge, top left) under 100% stretching toward (ii) X-, (iii) Y-, and (iv) XY-direction. Insets arehigh magnification SEM images showing the corresponding angle changes between neighboring yarns. Scale bars are 500 nm.

ACS Applied Materials & Interfaces Research Article

DOI: 10.1021/acsami.7b14981ACS Appl. Mater. Interfaces 2017, 9, 41363−41370

41365

terized under those three different modes. Figures 2a and 2bshow the electrical stabilities of PANI/CNT/textile and CNT/textile (without PANI layer) under bending and twisting,illustrated by the variation of relative resistance, i.e., R/R0,where R0 and R correspond to the electrical resistance beforeand after deformation, respectively. Interestingly, severebending to a small radius of 0.1 cm and strong twisting to180° cause a minor enhancement of electrical conductivity.While the preexisting electrical junctions among CNTsreinforced by PANI layer are well maintained, additionalphysical electrical contacts can be supplemented under thegeometric buckling or wrinkling of textile. The electricalproperty of our energy textile is also endurable for repeateddeformation cycles. After 10000 cycles of bending or twisting,only a 2% increase in the electrical resistance was measured(Figure S8).Figure 2c compares the uniaxial stretchability of PANI/

CNT/textile and CNT/textile, evaluated by the variation ofRuni/R0 under tensile stretching toward X-, Y-, or XY-direction,as defined in Figure 2d. For the 50% of X-, Y-, and XY-directional stretching of CNT/textiles, R/R0 values weremeasured to be 2.06, 1.64, and 1.11, respectively. This direction

dependency is obviously ascribed to the anisotropic wovenstructure of textile. Figure 2d compares the configurationalmodification of yarns and bundles under stretching towarddifferent directions, observed by scanning electron microscopy(SEM). Given the intrinsic electrical properties of eachcomponent, the overall electrical conductivity of textile isdetermined by the areal density of conductive components(CNTs and PANI) as well as effective electrical junctionsbetween them. The characteristic angle between neighboringwoven bundles, denoted by the inner angle of V-shape (insetsin Figure 2d), strongly depends on the stretching direction.31 Asmaller angle may offer a tighter contact among CNT junctionswith larger contact area and lead to an enhanced electricalconnectivity. The angles for XY- and Y-directional stretchingwere 31° and 61°, which is smaller than unstretched state(66°). By contrast, X-directional stretching leads to a largeincrease in angle (77°) as well as sparse configuration ofbundles.As shown in Figure 2c, the electrical stability under stretching

is remarkably improved by in situ polymerized PANI layer(Figure S9). PANI/CNT/textile exhibited 1.15, 1.06, and 0.94of Runi/R0 values at the 50% of X-, Y-, and XY-directional

Figure 3. Quantitative evaluation of omnidirectional deformability. (a) Schematic illustration of quantitative evaluation method for omnidirectionalstretchability (top) and real experimental setup (bottom). (b) SEM images of textiles under omnidirectional stretching. Insets are high magnifiedSEM images showing the corresponding angle changes between neighboring yarns. Scale bars are 500 nm. (c) Variation of electrical resistance ofPANI/CNT/textile and CNT/textile under omnidirectional tensile loading. (d) Cycle stability of PANI/CNT/textile (closed symbols) and CNT/textile (open symbols) with repeated 20% omnidirectional stretching.

ACS Applied Materials & Interfaces Research Article

DOI: 10.1021/acsami.7b14981ACS Appl. Mater. Interfaces 2017, 9, 41363−41370

41366

stretching, respectively. Conformal coating of PANI improvesthe electrical connectivity among CNT strands as well asPANI/CNT/polymer yarns by filling the voids among them. Italso enhances the mechanical stability of electrical contactjunctions and tightens the overlap among woven yarns. Thesynergistic effect from CNT and PANI coating strengthens theelectrical connectivity and prevents the delamination andfracture of composite structure even under severe complexdeformation (Figures S10−S12).Omnidirectional Stretchability of Energy Textile.

Omnidirectional stretchability of our energy textile wasquantitatively evaluated, as illustrated in Figure 3a. For anequivalent tensile stretching toward every direction, we used asolid sphere tensile loader. The sphere-loaded textile surfacegenerates isotropic tensile strains from the tangent points withsphere surface to every direction. The applied tensile strain canbe quantified by the ratio of initial length (L0) to a lengthincrement (L − L0) of specimen. The magnitude of stretchingwas simply controlled by the vertical location of spherical

loader. Investigation on the variation of electrical stability(Romni/R0) along with the degree of omnidirectional stretchingrationally quantifies the omnidirectional stretchability of aspecimen. Notably, this evaluation method also facilitates thediverse stretching situations with different surface curvatures byemploying different radius of sphere loader (Figure S13). Forinstance, stretching and bending motions on the knee, theelbow, and the knuckle have different surface curvatures. Theradius of curvature of sphere loader used in this work was 11mm, which can cover human’s motions on knee, shoulder, andelbow, on which the radii of curvatures are known to be 20 mmand over.46,47

According to the suggested methodology, we evaluated theomnidirectional stretchability of PANI/CNT/textile. Polymer-free textile (CNT/textile) was investigated again as a referenceto verify the reinforcing effect from PANI layer. Figure 3bshows SEM image of omnidirectionally stretched PANI/CNT/textile. Figure 3c presents that PANI/CNT/textile exhibits avery small increase of Romni/R0 up to 20%, followed by gradual

Figure 4. Electrochemical capacitors made from PANI/CNT/textile and CNT/textile. (a) Device configuration of electrochemical capacitorsassembled from textile electrodes and phosphoric acid/PVA gel electrolyte. (b) Cyclic voltammograms of textile-based electrochemical capacitors atvarious scan rates. (c) Areal specific capacitance vs current density. (d) Schematic illustration of evaluation method for omnidirectional stretchabilityof electrochemical capacitors. (e) Galvanostatic charge/discharge curves under various omnidirectional stretching levels. (f) Capacitance retentionunder various omnidirectional stretching levels. (g) Cycle stability of PANI/CNT/textile capacitors under repeated 20% omnidirectional stretching.(h) Ragone plot with previously reported stretchable electrochemical capacitors. (i) Red LED lightening powered by three PANI/CNT/textileelectrochemical capacitors in a series under omnidirectional stretching with finger pressure.

ACS Applied Materials & Interfaces Research Article

DOI: 10.1021/acsami.7b14981ACS Appl. Mater. Interfaces 2017, 9, 41363−41370

41367

decline even below the initial resistance value. Noteworthy thatthe variation of Romni/R0 shows a similar trend with that of Runi/R0 for unidirectional tensile stretching (Figure S14). The exactresistance variation follows the order of Runi‑XY/R0 < Romni/R0 <Runi‑X/R0. Approximately, omnidirectional stretching can beregarded as the summation of tensile stretching over all radialdirections. The equivalent circuit may be simply displayed withthe parallel circuits of all radical resistor components (FigureS15). According to Ohm’s law, the smallest resistor governs thetotal resistance of a parallel electric circuit. Consequently, theRomni/R0 stretching follows the minimum R/R0 curve forunidirectional stretching, i.e., the Runi‑XY/R0 for XY-directionalstretching. CNT/textile showed a similar tendency in theelectrical behavior. However, electrical stability is noticeablypoor without PANI layer. Figure 3d shows the cycle stability forrepeated omnidirectional stretching. PANI/CNT/textile ishighly reliable even after the repeated 50% omnidirectionalstretching up to 2000 cycles (Romni/R0 increase: 5%).Energy Storage/Supply Capability of Textile-Based

Electrochemical Capacitors under OmnidirectionalStretching. Electrochemical performances of PANI/CNT/textile- and CNT/textile-based electrochemical capacitors werecharacterized in a symmetric device configuration. The deviceswere composed of textile separators infiltrated with poly(vinylalcohol) (PVA)/H3PO4 aqueous gel electrolyte, sandwichedbetween two textile electrodes (Figure 4a and Figure S16).Cyclic voltammetry (CV) and galvanostatic charge/dischargecycles were measured between 0 and 0.8 V. Figure 4b showsthe CV curves for scan rates from 5 to 40 mV s−1. Compared toCNT/textile capacitor, PANI/CNT/textile-capacitor showssubstantially large inner area of CV curve, owing to the redoxactivity of PANI layer.48,49 Figure S17 presents the typicalcharge/discharge profiles for current densities from 0.2 to 0.8mA cm−2 (current: 0.5 to 2 mA). The specific areal capacitanceof PANI/CNT/textile capacitor reaches 412 mF cm−2 at 0.5mA cm−2, which is about 80-fold enhancement from CNT/textile capacitor (Figure 4c). The specific gravimetriccapacitance of PANI/CNT/textile capacitor was also calculatedto be 211 F g−1 at 0.2 mA cm−2, comparable to those of highperformance PANI-based electrochemical capacitors (withoutmechanical deformability) reported thus far.50,51 Additionally,textile capacitors showed an outstanding stability up to 10000cycles of charge/discharge (Figure S18). The capacitance ofPANI/CNT/textile capacitor gradually increased up to 5000cycles primarily due to the electrochemical activation of PANIand the improvement in the wetting of gel electrolyte at textilesurfaces.Figure 4d is a schematic illustration of the omnidirectional

stretchability of our PANI/CNT/textile capacitor. Dischargeprofiles in the galvanostatic measurements show no distinctmodification under the omnidirectional stretching up to 50%(Figure 4e). Energy capacity retained 95% of originalcapacitance (Figure 4f) and, moreover, maintained 93% ofcapacitance after 2000 cycles of stretching (Figure 4g). Whilethe electrochemical activity of energy textile is dominated byCNT and PANI layers, their effective surface area and electricalconductivity are well-preserved under the severe deformation oftextile. We also evaluated our textile capacitors under bendingand twisting deformations. The capacitors retained theiroriginal CV curves under harsh bending up to 0.1 cm bendingradius and 90° twisting condition (Figure S19). Even under adynamic strain operation, the electrochemical performance waswell-maintained with stable CV curves (Movie S1). Ragone plot

in Figure 4h compares the areal (red circles) and gravimetric(blue circle) power and energy densities of PANI/CNT/textilecapacitor with other uniaxial or biaxial stretchable electro-chemical capacitors reported thus far.13,17,18,52−57 The maximalareal and gravimetric energy densities of the as-prepared deviceare 36.7 μWh cm−2 and 18.7 Wh kg−1 with high powerdensities of 0.11 mW cm−2 and 58.3 W kg−1, respectively. Theoutstanding energy storage/supply capability retained 95% oforiginal energy and power densities under 50% omnidirectionalstretching (star). As a demonstration of device application,three 25 cm2 PANI/CNT/textile capacitors with PVA/LiCl gelelectrolyte were serially connected to light up a red light-emitting diode (LED) (Figure S20). By virtue of high energycapacity of our devices, the LED lighting prolonged over 1 hwith a single full charge. The sustainability of LED lighting wasalso tested under repeated omnidirectional stretching/releasing.Interestingly, LED maintained its original brightness withoutany noticeable flickering or diminishing of intensity under thedynamic deformation cycles, as shown in Figure 4i (Movie S2).The energy textile capacitors could also be integrated into ourdaily clothes as wearable power sources compatible to humanelbow joint motion for lighting LED (Movie S3 and Movie S4).

■ CONCLUSIONElectrochemically active hybrid textile structure is introducedfor the high performance wearable energy storage adaptable tothe complex omnidirectional deformation at human joints. Theplatform presented here relies on three key design features fortruly wearable power devices: (1) providing omnidirectionaldeformability with elastic and woven substrate structure, (2)retaining electrical activity for energy delivery under repeatedmechanical deformation with robust interfacial treatment withCNT/conductive polymer layer, and (3) facilitating activeredox behavior for high energy storage with in situ polymerizedconductive polymers. Significantly, intimate conformal inter-facial growth of conductive polymers effectively strengthen thephysical junctions among one-dimensional CNT strands suchthat electrical conductive pathway through CNT networkstructure is well-sustained even under complex largedeformation modes and provides highly stable electrical andelectrochemical performances. This rational material design andintegration concept represents a typical instance generallyapplicable to many different wearable devices other than energystorage. We also propose a methodology for the quantitativeevaluation of omnidirectional stretchability for functionalmaterials and devices, while imposing well-defined deformationanalogous to human joint motion. Overall, this study definesthe importance of deformability toward arbitrary direction forthe practical utilization of wearable materials and devices andsuggests a viable way to cloth-integrated electronics.

■ ASSOCIATED CONTENT

*S Supporting InformationThe Supporting Information is available free of charge on theACS Publications website at DOI: 10.1021/acsami.7b14981.

Experimental procedures and materials characterization,Scheme S1, Figures S1−S20 (PDF)Movie S1 (AVI)Movie S2 (AVI)Movie S3 (AVI)Movie S4 (AVI)

ACS Applied Materials & Interfaces Research Article

DOI: 10.1021/acsami.7b14981ACS Appl. Mater. Interfaces 2017, 9, 41363−41370

41368

■ AUTHOR INFORMATIONCorresponding Author*E-mail: sangouk.kim@kaist.ac.kr (S.O.K.).ORCIDSang Ouk Kim: 0000-0003-1513-6042Author ContributionsJ.L. principally performed the experiments and leaded thisproject. S.O.K. supervised the entire project. S.O.K. and J.L.conceived the idea and designed the overall experiments. J.L.,H.J.L., S.P.S., and S.H.K. carried out the materials synthesis,characterizations, and fabrication of textile-based capacitors.D.S.C., G.Y.L., and K.E.L. performed X-ray photoelectronspectroscopy and Raman spectroscopy measurements andanalyzed the results. All authors cowrote the paper andparticipated in discussions.NotesThe authors declare no competing financial interest.

■ ACKNOWLEDGMENTSThis work was supported by the KOLON Corporation, Korea,through the KOLON-KAIST Lifestyle Innovation CenterProject (LSI14-MAKSW0001), the Multi-Dimensional Direc-ted Nanoscale Assembly Creative Research Initiative (CRI)Center (2015R1A3A2033061), and the Nano-Material Tech-nology Development Program through the National ResearchFoundation of Korea (NRF) funded by the Ministry of Science,ICT and Future Planning (2016M3A7B4905613).

■ REFERENCES(1) Kim, D.-H.; Lu, N.; Ma, R.; Kim, Y.-S.; Kim, R.-H.; Wang, S.; Wu,J.; Won, S. M.; Tao, H.; Islam, A.; et al. Epidermal Electronics. Science2011, 333, 838−843.(2) Kim, D.-H.; Ahn, J.-H.; Choi, W. M.; Kim, H.-S.; Kim, T.-H.;Song, J.; Huang, Y. Y.; Liu, Z.; Lu, C.; Rogers, J. A. Stretchable andFoldable Silicon Integrated Circuits. Science 2008, 320, 507−511.(3) Park, S.-I.; Xiong, Y.; Kim, R.-H.; Elvikis, P.; Meitl, M.; Kim, D.-H.; Wu, J.; Yoon, J.; Yu, C.-J.; Liu, Z.; et al. Printed Assemblies ofInorganic Light-Emitting Diodes for Deformable and SemitransparentDisplays. Science 2009, 325, 977−981.(4) Son, D.; Lee, J.; Qiao, S.; Ghaffari, R.; Kim, J.; Lee, J. E.; Song, C.;Kim, S. J.; Lee, D. J.; Jun, S. W.; et al. Multifunctional WearableDevices for Diagnosis and Therapy of Movement Disorders. Nat.Nanotechnol. 2014, 9, 397−404.(5) Pang, C.; Lee, G.-Y.; Kim, T.-i.; Kim, S. M.; Kim, H. N.; Ahn, S.-H.; Suh, K.-Y. A Flexible and Highly Sensitive Strain-Gauge SensorUsing Reversible Interlocking of Nanofibres. Nat. Mater. 2012, 11,795−801.(6) Kim, J.; Lee, M.; Shim, H. J.; Ghaffari, R.; Cho, H. R.; Son, D.;Jung, Y. H.; Soh, M.; Choi, C.; Jung, S.; et al. Stretchable SiliconNanoribbon Electronics for Skin Prosthesis. Nat. Commun. 2014, 5,5747.(7) Liu, L.; Yu, Y.; Yan, C.; Li, K.; Zheng, Z. Wearable Energy-Denseand Power-Dense Supercapacitor Yarns Enabled by ScalableGraphene-Metallic Textile Composite Electrodes. Nat. Commun.2015, 6, 7260.(8) Rogers, J. A.; Someya, T.; Huang, Y. Materials and Mechanics forStretchable Electronics. Science 2010, 327, 1603−1607.(9) Rogers, J. A.; Huang, Y. A Curvy, Stretchy Future for Electronics.Proc. Natl. Acad. Sci. U. S. A. 2009, 106, 10875−10876.(10) Khang, D.-Y.; Jiang, H.; Huang, Y.; Rogers, J. A. A StretchableForm of Single-Crystal Silicon for High-Performance Electronics onRubber Substrates. Science 2006, 311, 208−212.(11) Sun, Y.; Choi, W. M.; Jiang, H.; Huang, Y. Y.; Rogers, J. A.Controlled Buckling of Semiconductor Nanoribbons for StretchableElectronics. Nat. Nanotechnol. 2006, 1, 201−207.

(12) Xu, S.; Zhang, Y.; Cho, J.; Lee, J.; Huang, X.; Jia, L.; Fan, J. A.;Su, Y.; Su, J.; Zhang, H.; et al. Stretchable Batteries with Self-SimilarSerpentine Interconnects and Integrated Wireless Recharging Systems.Nat. Commun. 2013, 4, 1543.(13) Yu, C.; Masarapu, C.; Rong, J.; Wei, B.; Jiang, H. StretchableSupercapacitors Based on Buckled Single-Walled Carbon-NanotubeMacrofilms. Adv. Mater. 2009, 21, 4793−4797.(14) Qi, D.; Liu, Z.; Liu, Y.; Leow, W. R.; Zhu, B.; Yang, H.; Yu, J.;Wang, W.; Wang, H.; Yin, S.; Chen, X. Suspended Wavy GrapheneMicroribbons for Highly Stretchable Microsupercapacitors. Adv. Mater.2015, 27, 5559−5566.(15) Bae, J.; Song, M. K.; Park, Y. J.; Kim, J. M.; Liu, M.; Wang, Z. L.Fiber Supercapacitors Made of Nanowire-Fiber Hybrid Structures forWearable/Flexible Energy Storage. Angew. Chem., Int. Ed. 2011, 50,1683−1687.(16) Lee, J.; Kwon, H.; Seo, J.; Shin, S.; Koo, J. H.; Pang, C.; Son, S.;Kim, J. H.; Jang, Y. H.; Kim, D. E.; Lee, T. Conductive Fiber-BasedUltrasensitive Textile Pressure Sensor for Wearable Electronics. Adv.Mater. 2015, 27, 2433−2439.(17) Chen, X.; Qiu, L.; Ren, J.; Guan, G.; Lin, H.; Zhang, Z.; Chen,P.; Wang, Y.; Peng, H. Novel Electric Double-Layer Capacitor with aCoaxial Fiber Structure. Adv. Mater. 2013, 25, 6436−6441.(18) Yang, Z.; Deng, J.; Chen, X.; Ren, J.; Peng, H. A HighlyStretchable, Fiber-Shaped Supercapacitor. Angew. Chem., Int. Ed. 2013,52, 13453−13457.(19) Kou, L.; Huang, T.; Zheng, B.; Han, Y.; Zhao, X.; Gopalsamy,K.; Sun, H.; Gao, C. Coaxial Wet-Spun Yarn Supercapacitors for High-Energy Density and Safe Wearable Electronics. Nat. Commun. 2014, 5,3754.(20) Chen, T.; Hao, R.; Peng, H.; Dai, L. High-Performance,Stretchable, Wire-Shaped Supercapacitors. Angew. Chem., Int. Ed. 2015,127, 628.(21) Zeng, W.; Shu, L.; Li, Q.; Chen, S.; Wang, F.; Tao, X. M. Fiber-Based Wearable Electronics: A Review of Materials, Fabrication,Devices, and Applications. Adv. Mater. 2014, 26, 5310−5336.(22) Shim, B. S.; Chen, W.; Doty, C.; Xu, C.; Kotov, N. A. SmartElectronic Yarns and Wearable Fabrics for Human BiomonitoringMade by Carbon Nanotube Coating with Polyelectrolytes. Nano Lett.2008, 8, 4151−4157.(23) Zhang, D.; Miao, M.; Niu, H.; Wei, Z. Core-Spun CarbonNanotube Yarn Supercapacitors for Wearable Electronic Textiles. ACSNano 2014, 8, 4571−4579.(24) Huang, Y.; Hu, H.; Huang, Y.; Zhu, M.; Meng, W.; Liu, C.; Pei,Z.; Hao, C.; Wang, Z.; Zhi, C. From Industrially Weavable andKnittable Highly Conductive Yarns to Large Wearable Energy StorageTextiles. ACS Nano 2015, 9, 4766−4775.(25) Gibbs, P. T.; Asada, H. Wearable Conductive Fiber Sensors forMulti-Axis Human Joint Angle Measurements. J. Neuroeng. Rehabil.2005, 2, 7.(26) Fan, J. A.; Yeo, W.-H.; Su, Y.; Hattori, Y.; Lee, W.; Jung, S.-Y.;Zhang, Y.; Liu, Z.; Cheng, H.; Falgout, L.; et al. Fractal DesignConcepts for Stretchable Electronics. Nat. Commun. 2014, 5, 3266.(27) Yu, J.; Lu, W.; Pei, S.; Gong, K.; Wang, L.; Meng, L.; Huang, Y.;Smith, J. P.; Booksh, K. S.; Li, Q.; et al. Omnidirectionally StretchableHigh-Performance Supercapacitor Based on Isotropic Buckled CarbonNanotube Films. ACS Nano 2016, 10, 5204−5211.(28) Nam, I.; Bae, S.; Park, S.; Yoo, Y. G.; Lee, J. M.; Han, J. W.; Yi, J.Omnidirectionally Stretchable, High Performance SupercapacitorsBased on a Graphene−Carbon-Nanotube Layered Structure. NanoEnergy 2015, 15, 33−42.(29) Hu, L.; Pasta, M.; La Mantia, F.; Cui, L.; Jeong, S.; Deshazer, H.D.; Choi, J. W.; Han, S. M.; Cui, Y. Stretchable, Porous, andConductive Energy Textiles. Nano Lett. 2010, 10, 708−714.(30) Jost, K.; Stenger, D.; Perez, C. R.; McDonough, J. K.; Lian, K.;Gogotsi, Y.; Dion, G. Knitted and Screen Printed Carbon-FiberSupercapacitors for Applications in Wearable Electronics. EnergyEnviron. Sci. 2013, 6, 2698−2705.

ACS Applied Materials & Interfaces Research Article

DOI: 10.1021/acsami.7b14981ACS Appl. Mater. Interfaces 2017, 9, 41363−41370

41369

(31) Lee, Y.-H.; Kim, Y.; Lee, T.-I.; Lee, I.; Shin, J.; Lee, H. S.; Kim,T.-S.; Choi, J. W. Anomalous Stretchable Conductivity Using anEngineered Tricot Weave. ACS Nano 2015, 9, 12214−12223.(32) Pu, X.; Liu, M.; Li, L.; Han, S.; Li, X.; Jiang, C.; Du, C.; Luo, J.;Hu, W.; Wang, Z. L. Wearable Textile-Based in-Plane Micro-supercapacitors. Adv. Energy Mater. 2016, 6, 1601254.(33) Sekitani, T.; Noguchi, Y.; Hata, K.; Fukushima, T.; Aida, T.;Someya, T. A Rubberlike Stretchable Active Matrix Using ElasticConductors. Science 2008, 321, 1468−1472.(34) Jost, K.; Perez, C. R.; McDonough, J. K.; Presser, V.; Heon, M.;Dion, G.; Gogotsi, Y. Carbon Coated Textiles for Flexible EnergyStorage. Energy Environ. Sci. 2011, 4, 5060−5067.(35) Bao, L.; Li, X. Towards Textile Energy Storage from Cotton T-shirts. Adv. Mater. 2012, 24, 3246−3252.(36) Pu, X.; Li, L.; Liu, M.; Jiang, C.; Du, C.; Zhao, Z.; Hu, W.;Wang, Z. L. Wearable Self-Charging Power Textile Based on FlexibleYarn Supercapacitors and Fabric Nanogenerators. Adv. Mater. 2016,28, 98−105.(37) Liu, B.; Zhang, J.; Wang, X.; Chen, G.; Chen, D.; Zhou, C.;Shen, G. Hierarchical Three-Dimensional Znco2o4 Nanowire Arrays/Carbon Cloth Anodes for a Novel Class of High-Performance FlexibleLithium-Ion Batteries. Nano Lett. 2012, 12, 3005−3011.(38) Lee, Y.-H.; Kim, J.-S.; Noh, J.; Lee, I.; Kim, H. J.; Choi, S.; Seo,J.; Jeon, S.; Kim, T.-S.; Lee, J.-Y.; Choi, J. W. Wearable Textile BatteryRechargeable by Solar Energy. Nano Lett. 2013, 13, 5753−5761.(39) Maiti, U. N.; Lim, J.; Lee, K. E.; Lee, W. J.; Kim, S. O. Three-Dimensional Shape Engineered, Interfacial Gelation of ReducedGraphene Oxide for High Rate, Large Capacity Supercapacitors.Adv. Mater. 2014, 26, 615−619.(40) Zhao, C.; Shu, K.; Wang, C.; Gambhir, S.; Wallace, G. G.Reduced Graphene Oxide and Polypyrrole/Reduced Graphene OxideComposite Coated Stretchable Fabric Electrodes for SupercapacitorApplication. Electrochim. Acta 2015, 172, 12−19.(41) Sun, J.; Huang, Y.; Fu, C.; Wang, Z.; Huang, Y.; Zhu, M.; Zhi,C.; Hu, H. High-Performance Stretchable Yarn Supercapacitor Basedon Ppy@ CNTs@ Urethane Elastic Fiber Core Spun Yarn. NanoEnergy 2016, 27, 230−237.(42) Haq, A. U.; Lim, J.; Yun, J. M.; Lee, W. J.; Han, T. H.; Kim, S.O. Direct Growth of Polyaniline Chains from N-Doped Sites ofCarbon Nanotubes. Small 2013, 9, 3829−3833.(43) Maiti, U. N.; Lee, W. J.; Lee, J. M.; Oh, Y.; Kim, J. Y.; Kim, J. E.;Shim, J.; Han, T. H.; Kim, S. O. 25th Anniversary Article: ChemicallyModified/Doped Carbon Nanotubes & Graphene for OptimizedNanostructures & Nanodevices. Adv. Mater. 2014, 26, 40−67.(44) Caracciolo, P.; Buffa, F.; Abraham, G. Effect of the HardSegment Chemistry and Structure on the Thermal and MechanicalProperties of Novel Biomedical Segmented Poly (Esterurethanes). J.Mater. Sci.: Mater. Med. 2009, 20, 145−155.(45) Rodrigues, P. C.; Akcelrud, L. Networks and Blends ofPolyaniline and Polyurethane: Correlations between Composition andThermal, Dynamic Mechanical and Electrical Properties. Polymer2003, 44, 6891−6899.(46) Stupar, D. Z.; Bajic, J. S.; Manojlovic, L. M.; Slankamenac, M. P.;Joza, A. V.; Zivanov, M. B. Wearable Low-Cost System for HumanJoint Movements Monitoring Based on Fiber-Optic Curvature Sensor.IEEE Sens. J. 2012, 12, 3424−3431.(47) Iannotti, J. P.; Gabriel, J. P.; Schneck, S.; Evans, B.; Misra, S. TheNormal Glenohumeral Relationships. An Anatomical Study of OneHundred and Forty Shoulders. J. Bone Joint Surg. Am. 1992, 74, 491−500.(48) Lim, J.; Maiti, U. N.; Kim, N.-Y.; Narayan, R.; Lee, W. J.; Choi,D. S.; Oh, Y.; Lee, J. M.; Lee, G. Y.; Kang, S. H.; Kim, H.; Kim, Y-. H.;Kim, S. O. Dopant-Specific Unzipping of Carbon Nanotubes for IntactCrystalline Graphene Nanostructures. Nat. Commun. 2016, 7, 10364.(49) Liu, J.; Jiang, J.; Cheng, C.; Li, H.; Zhang, J.; Gong, H.; Fan, H.J. Co3O4 Nanowire@ MnO2 Ultrathin Nanosheet Core/Shell Arrays:A New Class of High-Performance Pseudocapacitive Materials. Adv.Mater. 2011, 23, 2076−2081.

(50) Wu, Q.; Xu, Y.; Yao, Z.; Liu, A.; Shi, G. Supercapacitors Basedon Flexible Graphene/Polyaniline Nanofiber Composite Films. ACSNano 2010, 4, 1963−1970.(51) Kumar, N. A.; Choi, H.-J.; Shin, Y. R.; Chang, D. W.; Dai, L.;Baek, J.-B. Polyaniline-Grafted Reduced Graphene Oxide for EfficientElectrochemical Supercapacitors. ACS Nano 2012, 6, 1715−1723.(52) Chen, T.; Peng, H.; Durstock, M.; Dai, L. High-PerformanceTransparent and Stretchable All-Solid Supercapacitors Based onHighly Aligned Carbon Nanotube Sheets. Sci. Rep. 2015, 4, 3612.(53) Zhang, N.; Zhou, W.; Zhang, Q.; Luan, P.; Cai, L.; Yang, F.;Zhang, X.; Fan, Q.; Zhou, W.; Xiao, Z.; et al. Biaxially StretchableSupercapacitors Based on the Buckled Hybrid Fiber Electrode Array.Nanoscale 2015, 7, 12492−12497.(54) Tamilarasan, P.; Ramaprabhu, S. Stretchable SupercapacitorsBased on Highly Stretchable Ionic Liquid Incorporated PolymerElectrolyte. Mater. Chem. Phys. 2014, 148, 48−56.(55) Meng, Y.; Zhao, Y.; Hu, C.; Cheng, H.; Hu, Y.; Zhang, Z.; Shi,G.; Qu, L. All-Graphene Core-Sheath Microfibers for All-Solid-State,Stretchable Fibriform Supercapacitors and Wearable ElectronicTextiles. Adv. Mater. 2013, 25, 2326−2331.(56) Xu, P.; Kang, J.; Choi, J.-B.; Suhr, J.; Yu, J.; Li, F.; Byun, J.-H.;Kim, B.-S.; Chou, T.-W. Laminated Ultrathin Chemical VaporDeposition Graphene Films Based Stretchable and TransparentHigh-Rate Supercapacitor. ACS Nano 2014, 8, 9437−9445.(57) Xu, P.; Gu, T.; Cao, Z.; Wei, B.; Yu, J.; Li, F.; Byun, J. H.; Lu,W.; Li, Q.; Chou, T. W. Carbon Nanotube Fiber Based StretchableWire-Shaped Supercapacitors. Adv. Energy Mater. 2014, 4, 1300759.

ACS Applied Materials & Interfaces Research Article

DOI: 10.1021/acsami.7b14981ACS Appl. Mater. Interfaces 2017, 9, 41363−41370

41370