Skin-like stretchable sensors with the flexible and soft inorganic/organic electronics have many promising potentials in wearable devices, soft robotics, prosthetics, and health monitoring equipment. Hydrogels with ionic conduction, akin to the biological skin, provide an alternative for soft and stretchable sensor design. However, fully integrated and wearable sensing skin with ionically conductive hydrogel for hand-motion monitoring has not been achieved. In this article, we report a wearable soft ionotronic skin (iSkin) system integrating multichannel stretchable and transparent hydrogel–elastomer hybrid ionic sensors and a wireless electronic control module. The ionic sensor is of resistive type and fabricated by curing ionic hydrogel precursor on a benzophenone-treated preshaped elastomer to form a hydrogel–elastomer hybrid structure. The hydrogel–elastomer hybrid iSkin is highly stretchable (∼300% strain), transparent (∼95% transmittance in the visible light range), and lightweight (<22 g). Experiments demonstrate that the fully integrated iSkin system can conformably attach onto the dexterous hands for recognizing the joint proprioception and hand gesture, and understanding the sign language. Our iSkin system would also provide a test bed for customized material selection and construction in a variety of applications.
RogersJA, SomeyaT, HuangY. Materials and mechanics for stretchable electronics. Science, 2010; 327:1603–1607.
3.
SonD, KangJ, VardoulisO, et al.An integrated self-healable electronic skin system fabricated via dynamic reconstruction of a nanostructured conducting network. Nat Nanotechnol, 2018; 13:1057–1065.
4.
BauerS, Bauer-GogoneaS, GrazI, et al.25th anniversary article: a soft future: from robots and sensor skin to energy harvesters. Adv Mater, 2014; 26:149–162.
5.
BernthaJE, HoV, LiuH. Morphological computation in haptic sensation and interaction: from nature to robotics. Adv Robotics, 2018; 32:340–362.
6.
HuL, ChenY, WangS, ChenZ. A fast, lightweight and accurate activity recognition model for mini-wearable devices. Pervasive Mob Comput, 2014; 15:200–214.
7.
KimDH, LuN, MaR, et al.Epidermal electronics. Science, 2011; 333:838–843.
8.
LuN, KimDH. Flexible and stretchable electronics paving the way for soft robotics. Soft Robot, 2014; 1:53–62.
9.
LiuY, NortonJ, QaziR, et al.Epidermal mechano-acoustic sensing electronics for cardiovascular diagnostics and human-machine interfaces. Sci Adv, 2016; 2:e1601185.
10.
JangKI, LiK, ChungHUet al.Self-assembled three dimensional network designs for soft electronics. Nat Commun, 2017; 8:15894.
11.
WagnerS, BauerS. Materials for stretchable electronics. MRS Bull, 2012; 37:207–213.
12.
HammockML, ChortosA, TeeB, et al.25th anniversary article: the evolution of electronic skin (e-skin): a brief history, design considerations, and recent progress. Adv Mater, 2013; 25:5997–6038.
13.
AmjadiM, KyungKU, ParkI, et al.Stretchable, skin-mountable, and wearable strain sensors and their potential applications: a review. Adv Funct Mater, 2016; 26:1678–1698.
14.
ChenD, PeiQ. Electronic muscles and skins: a review of soft sensors and actuators. Chem Rev, 2017; 117:11239–11268.
15.
KimHJ, SimK, ThukralA, et al.Rubbery electronics and sensors from intrinsically stretchable elastomeric composites of semiconductors and conductors. Sci Adv, 2017; 3:e1701114.
16.
MuthJT, VogtDM, TrubyRLet al.Embedded 3d printing of strain sensors within highly stretchable elastomers. Adv Mater, 2014; 26:6307–6312.
17.
BartlettMD, MarkvickaEJ, MajidiC. Rapid fabrication of soft, multilayered electronics for wearable biomonitoring. Adv Funct Mater, 2016; 26:8496–8504.
18.
O'ConnorTF, FachME, MillerR, et al.The Language of Glove: wireless gesture decoder with low-power and stretchable hybrid electronics. PLoS One, 2017; 12:e0179766.
19.
LiL, JiangS, ShullPBet al.Skingest: artificial skin for gesture recognition via filmy stretchable strain sensors. Adv Robot, 2018; 32:1112–1121.
20.
WangS, XuJ, WangW, et al.Skin electronics from scalable fabrication of an intrinsically stretchable transistor array. Nature, 2018; 555:83.
21.
KimHJ, ThukralA, YuC. Highly sensitive and very stretchable strain sensor based on a rubbery semiconductor. ACS Appl Mater Interfaces, 2018; 10:5000–5006.
22.
KimHJ, ThukralA, SharmaS, et al.Biaxially stretchable fully elastic transistors based on rubbery semiconductor nanocomposites. Adv Mater Technol, 2018; 3:1800043.
23.
YamadaT, HayamizuY, YamamotoY, et al.A stretchable carbon nanotube strain sensor for human-motion detection. Nat Nanotechnol, 2011; 6:296.
24.
LiQ, LiJ, TranD, et al.Engineering of carbon nanotube/polydimethylsiloxane nanocomposites with enhanced sensitivity for wearable motion sensors. J Mater Chem C, 2017; 5:11092–11099.
25.
HuN, ItoiT, AkagiT, et al.Ultrasensitive strain sensors made from metal-coated carbon nanofiller/epoxy composites. Carbon, 2013; 51:202–212.
ParkY, ChenB, WoodRJ. Design and fabrication of soft artificial skin using embedded microchannels and liquid conductors. IEEE Sens J, 2012; 12:2711–2718.
28.
LuT, FinkenauerL, WissmanJ, et al.Rapid prototyping for soft-matter electronics. Adv Funct Mater, 2014; 24:3351–3356.
29.
MarkvickaEJ, BartlettMD, HuangX, et al.An autonomously electrically self-healing liquid metal-elastomer composite for robust soft-matter robotics and electronics. Nat Mater, 2018; 17:618–624.
30.
GaoY, OtaH, SchalerEWet al.Wearable microuidic diaphragm pressure sensor for health and tactile touch monitoring. Adv Mater, 2017; 29:1701985.
LipomiDJ, VosgueritchianM, TeeCKet al.Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes. Nat Nanotechnol, 2011; 6:788–792.
37.
RamuzM, TeeB, TokJ, et al.Transparent, optical, pressure-sensitive artificial skin for large-area stretchable electronics. Adv Mater, 2012; 24:3223–3227.
38.
KimJ, LeeM, JeonS, et al.Highly transparent and stretchable field-effect transistor sensors using graphene-nanowire hybrid nanostructures. Adv Mater, 2015; 27:3292–3297.
39.
ZhaoX. Multi-scale multi-mechanism design of tough hydrogels: building dissipation into stretchy networks. Soft Matter, 2014; 10:672–687.
40.
LinS, YukH, ZhangT, et al.Stretchable hydrogel electronics and devices. Adv Mater, 2016; 28:4497–4505.
41.
YangC, ChenB, LuJ, et al.Ionic cable. Extreme Mech Lett, 2015; 3:59–65.
42.
YukH, ZhangT, ParadaGAet al.Skin-inspired hydrogel-elastomer hybrids with robust interfaces and functional microstructures. Nat Commun, 2016; 7:12028.
43.
LarsonC, PeeleB, LiS, et al.Highly stretchable electroluminescent skin for optical signaling and tactile sensing. Science, 2016; 351:1071–1074.
44.
TianK, BaeJ, BakarichSEet al.3D printing of transparent and conductive heterogeneous hydrogel-elastomer systems. Adv Mater, 2017; 29:1604827.
45.
KimSH, JungS, YoonISet al.Ultrastretchable conductor fabricated on skin-like hydrogel-elastomer hybrid substrates for skin electronics. Adv Mater, 2013; 30:1800109.
46.
QiuZ, WanY, ZhouW, et al.Ionic skin with biomimetic dielectric layer templated from calathea zebrine leaf. Adv Funct Mater, 2018; 28:1802343.
CaiG, WangJ, QianJ, et al.Extremely stretchable strain sensors based on conductive self-healing dynamic cross-links hydrogels for human-motion detection. Adv Sci, 2017; 4:1600190.
49.
LeiZ, WangQ, SunS, et al.A bioinspired mineral hydrogel as a self-healable, mechanically adaptable ionic skin for highly sensitive pressure sensing. Adv Mater, 2017; 29:1700321.
50.
WirthlD, PichlerR, DrackM, et al.Instant tough bonding of hydrogels for soft machines and electronics. Sci Adv, 2017; 3:e1700053.
BaiY, ChenB, XiangF, et al.Transparent hydrogel with enhanced water retention capacity by introducing highly hydratable salt. Appl Phys Lett, 2014; 105:151903.
PawlaczykM, LelonkiewiczM, WieczorowskiM. Age-dependent biomechanical properties of the skin. Adv Dermatol, 2013; 30:302–306.
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