Latest developments and trends in electronic skin devices

Abstract

The skin, a vital medium for human-environment communication, stands as an indispensable and pivotal element in the realms of both production and daily life. As the landscape of science and technology undergoes gradual evolution and the demand for seamless human-machine interfaces continues to surge, an escalating need emerges for a counterpart to our biological skin - electronic skins (e-skins). Achieving high-performance sensing capabilities comparable to our skin has consistently posed a formidable challenge. In this article, we systematically outline fundamental strategies enabling e-skins with capabilities including strain sensing, pressure sensing, shear sensing, temperature sensing, humidity sensing, and self-healing. Subsequently, complex e-skin systems and current major applications were briefly introduced. We conclude by envisioning the future trajectory, anticipating continued advancements and transformative innovations shaping the dynamic landscape of e-skin technology. This article provides a profound insight into the current state of e-skins, potentially inspiring scholars to explore new possibilities.

Keywords

Electronic skin / sensor / human-machine interface / multimodal / machine learning

References

[1] Lumelsky VJ,Wagner S.Sensitive skin.IEEE Sens J2001;1:41-51

[2] Abraira VE.The sensory neurons of touch.Neuron2013;79:618-39 PMCID:PMC3811145

[3] Amjadi M,Park I.Stretchable, skin-mountable, and wearable strain sensors and their potential applications: a review.Adv Funct Mater2016;26:1678-98

[4] Wang Y,Tan M,Liang S.Recent advances in hydrogel-based self-powered artificial skins for human-machine interfaces.Adv Intell Syst2023;5:2300162

[5] Heng W,Gao W.Flexible electronics and devices as human-machine interfaces for medical robotics.Adv Mater2022;34:e2107902 PMCID:PMC9035141

[6] Schwartz G,Mei J.Flexible polymer transistors with high pressure sensitivity for application in electronic skin and health monitoring.Nat Commun2013;4:1859

[7] Yao S,Song R.Nanomaterial-enabled flexible and stretchable sensing systems: processing, integration, and applications.Adv Mater2020;32:e1902343

[8] Takei K,Ho JC.Nanowire active-matrix circuitry for low-voltage macroscale artificial skin.Nat Mater2010;9:821-6

[9] Xu X,Liu H.Stretchable electronic facial masks for skin electroporation.Adv Funct Mater2024;34:2311144

[10] Ye Y,Gunawardane PDSH.Ultra-stretchable and environmentally resilient hydrogels via sugaring-out strategy for soft robotics sensing.Adv Funct Mater2024;2315184

[11] Ye Y,Zhu J.Ultrastretchable ionogel with extreme environmental resilience through controlled hydration interactions.Adv Funct Mater2023;33:2209787

[12] Zhu P,Sun H.3D printed cellulose nanofiber aerogel scaffold with hierarchical porous structures for fast solar-driven atmospheric water harvesting.Adv Mater2024;36:e2306653

[13] Chen F,Hu L.Bio-inspired artificial perceptual devices for neuromorphic computing and gesture recognition.Adv Funct Mater2023;33:2300266

[14] Zhan P,Wei W.Stretchable strain sensor with high sensitivity, large workable range and excellent breathability for wearable electronic skins.Compos Sci Technol2022;229:109720

[15] Bi Y,Zhang Y.Seconds timescale synthesis of highly stretchable antibacterial hydrogel for skin wound closure and epidermal strain sensor.Adv Healthc Mater2024;13:e2302810

[16] Roy S,Lee HP.3D printed electronic skin for strain, pressure and temperature sensing.Adv Funct Mater2024;2313575

[17] Jiang N,Hu D.Flexible, transparent, and antibacterial ionogels toward highly sensitive strain and temperature sensors.Chem Eng J2021;424:130418

[18] Wu Z,Liu R,Hou C.Synthesis of borophene on quartz towards hydroelectric generators.J Mater Chem A2022;10:8218-26

[19] Wang Y,Zhou J.Flexible and transparent cellulose-based ionic film as a humidity sensor.ACS Appl Mater Interfaces2020;12:7631-8

[20] Shen D,Xiao Y.Self-powered, rapid-response, and highly flexible humidity sensors based on moisture-dependent voltage generation.ACS Appl Mater Interfaces2019;11:14249-55

[21] Dai J,Lin X.Ultrafast response polyelectrolyte humidity sensor for respiration monitoring.ACS Appl Mater Interfaces2019;11:6483-90

[22] Wang Y,Zhang X.Strong, supertough and self-healing biomimetic layered nanocomposites enabled by reversible interfacial polymer chain sliding.Angew Chem Int Ed Engl2023;62:e202303446

[23] Pei D,Liu P.Reversible wet-adhesive and self-healing conductive composite elastomer of liquid metal.Adv Funct Mater2022;32:2204257

[24] Bunea AC,Laszlo EA.E-skin: the dawn of a new era of on-body monitoring systems.Micromachines2021;12:1091 PMCID:PMC8470991

[25] Hammock ML,Tee BC,Bao Z.25th anniversary article: the evolution of electronic skin (e-skin): a brief history, design considerations, and recent progress.Adv Mater2013;25:5997-6038

[26] Yang JC,Kwon SY,Bao Z.Electronic skin: recent progress and future prospects for skin-attachable devices for health monitoring, robotics, and prosthetics.Adv Mater2019;31:e1904765

[27] Chen J,Chang X.Recent progress in essential functions of soft electronic skin.Adv Funct Mater2021;31:2104686

[28] Li WD,Jia J.Recent advances in multiresponsive flexible sensors towards e-skin: a delicate design for versatile sensing.Small2022;18:e2103734

[29] Jung S,Kim J.Reverse-micelle-induced porous pressure-sensitive rubber for wearable human-machine interfaces.Adv Mater2014;26:4825-30

[30] Lee Y,Cho S.Bioinspired gradient conductivity and stiffness for ultrasensitive electronic skins.ACS Nano2021;15:1795-804

[31] Hou C,Zhang Q,Zhu M.Highly conductive, flexible, and compressible all-graphene passive electronic skin for sensing human touch.Adv Mater2014;26:5018-24

[32] Cai Y,Yang CW.Mixed-dimensional MXene-hydrogel heterostructures for electronic skin sensors with ultrabroad working range.Sci Adv2020;6:eabb5367 PMCID:PMC7695469

[33] Sharma S,Sharifuzzaman M,Park JY.Wearable capacitive pressure sensor based on MXene composite nanofibrous scaffolds for reliable human physiological signal acquisition.ACS Appl Mater Interfaces2020;12:22212-24

[34] Meng K,Wei W.Wearable pressure sensors for pulse wave monitoring.Adv Mater2022;34:e2109357

[35] Claver U, Zhao G. Recent progress in flexible pressure sensors based electronic skin.Adv Eng Mater2021;23:2001187

[36] Zhang S,Xia Z.A review of electronic skin: soft electronics and sensors for human health.J Mater Chem B2020;8:852-62

[37] Zhang J,Liu C.Porous nanocomposites with enhanced intrinsic piezoresistive sensitivity for bioinspired multimodal tactile sensors.Microsyst Nanoeng2024;10:19 PMCID:PMC10811241

[38] Duan L,Wieme T.Designing formulation variables of extrusion-based manufacturing of carbon black conductive polymer composites for piezoresistive sensing.Compos Sci Technol2019;171:78-85

[39] Ding Y,Onyilagha O,Zhu Z.Recent advances in flexible and wearable pressure sensors based on piezoresistive 3D monolithic conductive sponges.ACS Appl Mater Interfaces2019;11:6685-704

[40] Zheng S,Huang Y.Multifunctional and highly sensitive piezoresistive sensing textile based on a hierarchical architecture.Compos Sci Technol2020;197:108255

[41] Li K,Yi M.Graphene-based pressure sensor and strain sensor for detecting human activities.Smart Mater Struct2021;30:085027

[42] Zhai Y,Zhou K.Flexible and wearable carbon black/thermoplastic polyurethane foam with a pinnate-veined aligned porous structure for multifunctional piezoresistive sensors.Chem Eng J2020;382:122985

[43] Zheng Y,Lou Z,Han W.Ti₃C₂T_x quantum dots/leaf veins based sensors with ultra-broadrange high sensitivity.J Phys D Appl Phys2023;56:485402

[44] Oh J,Kim Y.Highly uniform and low hysteresis piezoresistive pressure sensors based on chemical grafting of polypyrrole on elastomer template with uniform pore size.Small2019;15:e1901744

[45] Sencadas V,Alici G.Environmentally friendly and biodegradable ultrasensitive piezoresistive sensors for wearable electronics applications.ACS Appl Mater Interfaces2020;12:8761-72

[46] Park J,Hong J.Tactile-direction-sensitive and stretchable electronic skins based on human-skin-inspired interlocked microstructures.ACS Nano2014;8:12020-9

[47] Park J,Hong J.Giant tunneling piezoresistance of composite elastomers with interlocked microdome arrays for ultrasensitive and multimodal electronic skins.ACS Nano2014;8:4689-97

[48] Ha M,Park J,Lee Y.Bioinspired interlocked and hierarchical design of ZnO nanowire arrays for static and dynamic pressure-sensitive electronic skins.Adv Funct Mater2015;25:2841-9

[49] Miao L,Song Y.Skin-inspired humidity and pressure sensor with a wrinkle-on-sponge structure.ACS Appl Mater Interfaces2019;11:39219-27

[50] Park J,Hong J.Tailoring force sensitivity and selectivity by microstructure engineering of multidirectional electronic skins.NPG Asia Mater2018;10:163-76

[51] Baek J,Mylvaganan M.Mold-free manufacturing of highly sensitive and fast-response pressure sensors through high-resolution 3D printing and conformal oxidative chemical vapor deposition polymers.Adv Mater2023;35:e2304070

[52] Mishra RB,Hussain AM.Flexible capacitive pressure sensors: recent progress on flexible capacitive pressure sensors: from design and materials to applications (Adv. Mater. Technol. 4/2021).Adv Mater Technol2021;6:2001023

[53] Wang H,Liu Z.Flexible capacitive pressure sensors for wearable electronics.J Mater Chem C2022;10:1594-605

[54] Lee J,Seo J.Conductive fiber-based ultrasensitive textile pressure sensor for wearable electronics.Adv Mater2015;27:2433-9

[55] Lipomi DJ,Tee BC.Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes.Nat Nanotechnol2011;6:788-92

[56] Li J,Tang Y.Touchable gustation via a hoffmeister gel iontronic sensor.ACS Nano2023;17:5129-39

[57] Chen W.Progress in achieving high-performance piezoresistive and capacitive flexible pressure sensors: a review.J MaterSci Technol2020;43:175-88

[58] Kang S,Lee S.Highly sensitive pressure sensor based on bioinspired porous structure for real-time tactile sensing.Adv Elect Mater2016;2:1600356

[59] Tee BC,Dunn RR,Eason E.Tunable flexible pressure sensors using microstructured elastomer geometries for intuitive electronics.Adv Funct Mater2014;24:5427-34

[60] Niu H,Yue W,Zhou W.Highly morphology-controllable and highly sensitive capacitive tactile sensor based on epidermis-dermis-inspired interlocked asymmetric-nanocone arrays for detection of tiny pressure.Small2020;16:e1904774

[61] Yao G,Cheng X.Bioinspired triboelectric nanogenerators as self-powered electronic skin for robotic tactile sensing.Adv Funct Mater2020;30:1907312

[62] Zhu M,Abdalla I,Li Z.Highly shape adaptive fiber based electronic skin for sensitive joint motion monitoring and tactile sensing.Nano Energy2020;69:104429

[63] Chen Y,Zhang F,Sun X.Recent progress in self-powered multifunctional e-skin for advanced applications.Exploration2022;2:20210112 PMCID:PMC10191004

[64] Meng X,Luo B.Rational design of cellulosic triboelectric materials for self-powered wearable electronics.Nanomicro Lett2023;15:124 PMCID:PMC10175533

[65] Wu M,Li D.Self-powered skin electronics for energy harvesting and healthcare monitoring.Mater Today Energy2021;21:100786

[66] Jiang Y,Li X.Stretchable, washable, and ultrathin triboelectric nanogenerators as skin-like highly sensitive self-powered haptic sensors.Adv Funct Mater2021;31:2005584

[67] Ma M,Zhao Z.Self-powered flexible antibacterial tactile sensor based on triboelectric-piezoelectric-pyroelectric multi-effect coupling mechanism.Nano Energy2019;66:104105

[68] Kwon SH,Jiang Z.Textured nanofibers inspired by nature for harvesting biomechanical energy and sensing biophysiological signals.Nano Energy2024;122:109334

[69] Yu Y,Ge H.A self-powered piezoelectric Poly(vinyl alcohol)/Polyvinylidene fluoride fiber membrane with alternating multilayer porous structure for energy harvesting and wearable sensors.Compos Sci Technol2024;247:110429

[70] Scheffler S.Piezoelectric fibers: processing and challenges.ACS Appl Mater Interfaces2022;14:16961-82

[71] Ghosh SK.Synergistically enhanced piezoelectric output in highly aligned 1D polymer nanofibers integrated all-fiber nanogenerator for wearable nano-tactile sensor.Nano Energy2018;53:245-57

[72] Huang A,Peng S,Peng X.Improved energy harvesting ability of single-layer binary fiber nanocomposite membrane for multifunctional wearable hybrid piezoelectric and triboelectric nanogenerator and self-powered sensors.ACS Nano2024;18:691-702

[73] Du H,Wang M.Electrospun elastic films containing AgNW-bridged MXene networks as capacitive electronic skins.ACS Appl Mater Interfaces2022;14:31225-33

[74] Wang H,Li B.Advances in carbon-based resistance strain sensors.ACS Appl Electron Mater2023;5:674-89

[75] Zhao Y,Li Y.Development and application of resistance strain force sensors.Sensors2020;20:5826 PMCID:PMC7602478

[76] Chen J,Cui X.An overview of stretchable strain sensors from conductive polymer nanocomposites.J Mater Chem C2019;7:11710-30

[77] Zhou M,Zhou Y,Wang S.Graphene-based strain sensor with sandwich structure and its application in bowel sounds monitoring.RSC Adv2022;12:29103-12 PMCID:PMC9555162

[78] Feng P,Zhong M.Integrated resistive-capacitive strain sensors based on polymer-nanoparticle composites.ACS Appl Nano Mater2020;3:4357-66

[79] Chen J,Yu Q.Strain sensing behaviors of stretchable conductive polymer composites loaded with different dimensional conductive fillers.Compos Sci Technol2018;168:388-96

[80] Ha S.Simple route to performance modulation of resistive strain sensor based on strain-engineered stretchable substrate with customized hard template.Compos Sci Technol2022;217:109111

[81] Zhou Y,Ren M.Significant stretchability enhancement of a crack-based strain sensor combined with high sensitivity and superior durability for motion monitoring.ACS Appl Mater Interfaces2019;11:7405-14

[82] Na HR,Jeon JH.Vertical graphene on flexible substrate, overcoming limits of crack-based resistive strain sensors.npj Flex Electron2022;6:2

[83] Qiao Y,Tian H.Multilayer graphene epidermal electronic skin.ACS Nano2018;12:8839-46

[84] Chen Z,Yu T.Sandwich-structured flexible PDMS@graphene multimodal sensors capable of strain and temperature monitoring with superlative temperature range and sensitivity.Compos Sci Technol2023;232:109881

[85] Fan M,Hu Y.A highly stretchable natural rubber/buckypaper/natural rubber (NR/N-BP/NR) sandwich strain sensor with ultrahigh sensitivity.Adv Compos Hybrid Mater2021;4:1039-47

[86] Han X,Wen S.High-performance stretchable strain sensor based on Ag nanoparticles sandwiched between two 3D-printed polyurethane fibrous textiles.Adv Elect Mater2021;7:2001242

[87] Yang YF,Pang Y.An ultrasensitive strain sensor with a wide strain range based on graphene armour scales.Nanoscale2018;10:11524-30

[88] Kang D,Choi YW.Ultrasensitive mechanical crack-based sensor inspired by the spider sensory system.Nature2014;516:222-6

[89] Chen Q,Wu M.Tough and fatigue-resistant anisotropic hydrogels via fiber reinforcement and magnetic field induction.Sci China Mater2023;66:4841-52

[90] Wang Q,Wang G,Ren X.Muscle-inspired anisotropic hydrogel strain sensors.ACS Appl Mater Interfaces2022;14:1921-8

[91] Chang X,Chen J,Guo Z.Advances in transparent and stretchable strain sensors.Adv Compos Hybrid Mater2021;4:435-50

[92] Lee CS,Kim S,Aghaloo T.Inspired by nature: facile design of nanoclay-organic hydrogel bone sealant with multifunctional properties for robust bone regeneration.Adv Funct Mater2020;30:2003717 PMCID:PMC7591105

[93] Afewerki S.Unlocking the power of multicatalytic synergistic transformation: toward environmentally adaptable organohydrogel.Adv Mater2024;36:e2306657

[94] Xie J,Fan L.Robust and stretchable Ti₃C₂T_x MXene/PEI conductive composite dual-network hydrogels for ultrasensitive strain sensing.Compos Part A Appl Sci Manuf2024;176:107833

[95] Lei D,Xi M,Li Y.Thermochromic and conductive hydrogels with tunable temperature sensitivity for dual sensing of temperature and human motion.J Mater Chem C2023;12:232-44

[96] Zhang X,Li H.High tensile properties, wide temperature tolerance, and DLP-printable eutectogels for microarrays wearable strain sensors.Chem Eng J2024;481:149004

[97] Kim J,Song M.A reversible, versatile skin-attached haptic interface platform with bioinspired interconnection architectures capable of resisting sweat and vibration.Adv Funct Mater2024;34:2311167

[98] Gao X,Fan X.Highly sensitive flexible strain sensor based on microstructured biphasic hydrogels for human motion monitoring.Front Mater Sci2023;17:230665

[99] Lu Y,Wang S.Ultradurable, freeze-resistant, and healable MXene-based ionic gels for multi-functional electronic skin.Nano Res2022;15:4421-30

[100] Li T,Li S,Sun J.Mechanically robust, elastic, and healable ionogels for highly sensitive ultra-durable ionic skins.Adv Mater2020;32:e2002706

[101] Mao Y,Wu Z.Thermochromic optical/electrical hydrated ionogel with anti-freezing and self-healing ability for multimodal sensor.Compos Commun2023;44:101769

[102] Chun S,Choi C.Bioinspired hairy skin electronics for detecting the direction and incident angle of airflow.ACS Appl Mater Interfaces2019;11:13608-15

[103] Ji B,Chen G.In situ assembly of a wearable capacitive sensor with a spine-shaped dielectric for shear-pressure monitoring.J Mater Chem C2020;8:15634-45

[104] Pang C,Kim TI.A flexible and highly sensitive strain-gauge sensor using reversible interlocking of nanofibres.Nat Mater2012;11:795-801

[105] Yu H,Wang J.Skin-inspired capacitive flexible tactile sensor with an asymmetric structure for detecting directional shear forces.Adv Sci2024;11:e2305883 PMCID:PMC10853706

[106] Zhu Y,Xie D.High-performance flexible tactile sensor enabled by multi-contact mechanism for normal and shear force measurement.Nano Energy2023;117:108862

[107] Chen H,Guo H.Hybrid porous micro structured finger skin inspired self-powered electronic skin system for pressure sensing and sliding detection.Nano Energy2018;51:496-503

[108] Joh H,Seong M,Oh SJ.Engineering the charge transport of Ag nanocrystals for highly accurate, wearable temperature sensors through all-solution processes.Small2017;13:1700247

[109] Jeon J,Bao Z.Flexible wireless temperature sensors based on Ni microparticle-filled binary polymer composites.Adv Mater2013;25:850-5

[110] Yamada S.Temperature sensor with a water-dissolvable ionic gel for ionic skin.ACS Appl Mater Interfaces2020;12:36449-57

[111] Ren X,Peng B.A low-operating-power and flexible active-matrix organic-transistor temperature-sensor array.Adv Mater2016;28:4832-8

[112] Tien NT,Kim DI.A flexible bimodal sensor array for simultaneous sensing of pressure and temperature.Adv Mater2014;26:796-804

[113] Nag A,Gawade DR.Graphene-based wearable temperature sensors: a review.Mater Design2022;221:110971

[114] Liu R,Cao M,Zhu R.Flexible temperature sensors.Front Chem2021;9:539678 PMCID:PMC8492987

[115] Wang L,Li G.Temperature and strain compensation for flexible sensors based on thermosensation.ACS Appl Mater Interfaces2020;12:1953-61

[116] Li Q,Tao XM.Review of flexible temperature sensing networks for wearable physiological monitoring.Adv Healthc Mater2017;6:1601371

[117] Li F,Lin X,Zhang T.Wearable temperature sensor with high resolution for skin temperature monitoring.ACS Appl Mater Interfaces2022;14:43844-52

[118] Zhang C,Han H,Xu W.Dopamine-triggered hydrogels with high transparency, self-adhesion, and thermoresponse as skinlike sensors.ACS Nano2021;15:1785-94

[119] Cao Z,Jiang L.Transparent, mechanically robust, and ultrastable ionogels enabled by hydrogen bonding between elastomers and ionic liquids.Mater Horiz2020;7:912-8

[120] Li Z,Zhou R.Temperature decoupling of a hydrogel-based strain sensor under a dynamic temperature field.Adv Mater Technol2023;8:2300404

[121] Jia H,Zhang X,Wang Y.Integrating ultra-thermal-sensitive fluids into elastomers for multifunctional flexible sensors.Adv Elect Mater2015;1:1500029

[122] Ge G,Qu X.Muscle-inspired self-healing hydrogels for strain and temperature sensor.ACS Nano2020;14:218-28

[123] Wang F,Cui X,Chang X.Wearable ionogel-based fibers for strain sensors with ultrawide linear response and temperature sensors insensitive to strain.ACS Appl Mater Interfaces2022;14:30268-78

[124] Zhang M,Zhang B.Electrochemical humidity sensor enabled self-powered wireless humidity detection system.Nano Energy2023;115:108745

[125] Gyu Son S,Kim S.Ultra-fast self-healable stretchable bio-based elastomer/graphene ink using fluid dynamics process for printed wearable sweat-monitoring sensor.Chem Eng J2023;454:140443

[126] Yin F,Qiu Z.Hybrid electronic skin combining triboelectric nanogenerator and humidity sensor for contact and non-contact sensing.Nano Energy2022;101:107541

[127] Kano S,Fujii M.Fast-response and flexible nanocrystal-based humidity sensor for monitoring human respiration and water evaporation on skin.ACS Sens2017;2:828-33

[128] Zhang D,Tang M.Recent progress of diversiform humidity sensors based on versatile nanomaterials and their prospective applications.Nano Res2023;16:11938-58

[129] Wang Y,Li T.Flexible capacitive humidity sensors based on ionic conductive wood-derived cellulose nanopapers.ACS Appl Mater Interfaces2020;12:41896-904

[130] Gu L,Cao JC.Piezoelectric active humidity sensors based on lead-free NaNbO₃ piezoelectric nanofibers.Sensors2016;16:833 PMCID:PMC4934259

[131] Boudaden J,Endres HE.Polyimide-based capacitive humidity sensor.Sensors2018;18:1516 PMCID:PMC5982669

[132] Hou C,Liu Y,Wu Z.Ultrasensitive humidity sensing and the multifunctional applications of borophene-MoS₂ heterostructures.J Mater Chem A2021;9:13100-8

[133] Liu X,Liu Y.Borophene and BC₂N quantum dot heterostructures: ultrasensitive humidity sensing and multifunctional applications.J Mater Chem A2023;11:24789-99

[134] Xu C,Lin M.Strengthened, antibacterial, and conductive flexible film for humidity and strain sensors.ACS Appl Mater Interfaces2020;12:35482-92

[135] Li T,Zhang H.A skin-conformal and breathable humidity sensor for emotional mode recognition and non-contact human-machine interface.npj Flex Electron2024;8:3

[136] Chen L,Liu Y.Flexible and transparent electronic skin sensor with sensing capabilities for pressure, temperature, and humidity.ACS Appl Mater Interfaces2023;15:24923-32

[137] Guo H,Zhou Z,Wei D.Transparent, flexible, and stretchable WS₂ based humidity sensors for electronic skin.Nanoscale2017;9:6246-53

[138] Duan Z,Jiang Y,Tai H.Amorphous carbon material of daily carbon ink: emerging applications in pressure, strain, and humidity sensors.J Mater Chem C2023;11:5585-600

[139] Wang W,Wang H.Gas-permeable highly sensitive nanomesh humidity sensor for continuous measurement of skin humidity.Adv Mater Technol2022;7:2200479

[140] Jeong W,Bae J,Lee S.Breathable nanomesh humidity sensor for real-time skin humidity monitoring.ACS Appl Mater Interfaces2019;11:44758-63

[141] Li T,Sun H.Porous ionic membrane based flexible humidity sensor and its multifunctional applications.Adv Sci2017;4:1600404

[142] Xu L,Chen X.Coolmax/graphene-oxide functionalized textile humidity sensor with ultrafast response for human activities monitoring.Chem Eng J2021;412:128639

[143] Niu G,Xue Y.Pencil-on-paper humidity sensor treated with nacl solution for health monitoring and skin characterization.Nano Lett2023;23:1252-60

[144] He J,Shi J.High performance humidity fluctuation sensor for wearable devices via a bioinspired atomic-precise tunable graphene-polymer heterogeneous sensing junction.Chem Mater2018;30:4343-54

[145] Liu K,Huang C.Flexible bioinspired healable antibacterial electronics for intelligent human-machine interaction sensing.Adv Sci2024;11:e2305672 PMCID:PMC10933681

[146] Wang Y,Zhang X.Ultrarobust, tough and highly stretchable self-healing materials based on cartilage-inspired noncovalent assembly nanostructure.Nat Commun2021;12:1291 PMCID:PMC7910491

[147] Khatib M,Saliba W.A multifunctional electronic skin empowered with damage mapping and autonomic acceleration of self-healing in designated locations.Adv Mater2020;32:e2000246

[148] Jun S,Lee H.Transparent, pressure-sensitive, and healable e-skin from a UV-cured polymer comprising dynamic urea bonds.J Mater Chem A2019;7:3101-11

[149] Liu R,Li S.Ultrathin, transparent, and robust self-healing electronic skins for tactile and non-contact sensing.Nano Energy2022;95:107056

[150] Wang S.Self-healing polymers.Nat Rev Mater2020;5:562-83

[151] Huynh TP,Haick H.Advanced materials for use in soft self-healing devices.Adv Mater2017;29

[152] Han S,Hu Z.A near-infrared light-promoted self-healing photothermally conductive polycarbonate elastomer based on Prussian blue and liquid metal for sensors.J Colloid Interface Sci2024;654:955-66

[153] Yeh C,Han T,Chen Y.Disulfide bond and Diels-Alder reaction bond hybrid polymers with high stretchability, transparency, recyclability, and intrinsic dual healability for skin-like tactile sensing.J Mater Chem A2021;9:6109-16

[154] Xun X,Zhao X.Highly robust and self-powered electronic skin based on tough conductive self-healing elastomer.ACS Nano2020;14:9066-72

[155] Gao Z,Han W.A self-healable bifunctional electronic skin.ACS Appl Mater Interfaces2020;12:24339-47

[156] Zhang Z,Yu H.Highly transparent, self-healable, and adhesive organogels for bio-inspired intelligent ionic skins.ACS Appl Mater Interfaces2020;12:15657-66

[157] Wu J,Wei Y.Ultrasensitive and stretchable temperature sensors based on thermally stable and self-healing organohydrogels.ACS Appl Mater Interfaces2020;12:19069-79

[158] Liao H,Wan P.Conductive MXene nanocomposite organohydrogel for flexible, healable, low-temperature tolerant strain sensors.Adv Funct Mater2019;29:1904507

[159] Liu J,Wang N,Li C.Nanofiber-reinforced transparent, tough, and self-healing substrate for an electronic skin with damage detection and program-controlled autonomic repair.Nano Energy2022;96:107108

[160] Wei P,Chen G.Conductive self-healing nanocomposite hydrogel skin sensors with antifreezing and thermoresponsive properties.ACS Appl Mater Interfaces2020;12:3068-79

[161] Chen X,Tian H.Self-healing and stretchable conductor based on embedded liquid metal patterns within imprintable dynamic covalent elastomer.J Mater Chem C2022;10:1039-47

[162] Wang S,Zhang L,Wang H.Skin-inspired antibacterial conductive hydrogels customized for wireless flexible sensor and collaborative wound healing.J Mater Chem A2023;11:14096-107

[163] Pan X,Guo R.An adaptive ionic skin with multiple stimulus responses and moist-electric generation ability.J Mater Chem A2020;8:17498-506

[164] Liu Z,Ren Y.Poly(ionic liquid) hydrogel-based anti-freezing ionic skin for a soft robotic gripper.Mater Horiz2020;7:919-27

[165] Wang Y,Zhan R.Tough but self-healing and 3D printable hydrogels for E-skin, E-noses and laser controlled actuators.J Mater Chem A2019;7:24814-29

[166] Cui X,Zhu Y.Natural sunlight-actuated shape memory materials with reversible shape change and self-healing abilities based on carbon nanotubes filled conductive polymer composites.Chem Eng J2020;382:122823

[167] Son D,Vardoulis O.An integrated self-healable electronic skin system fabricated via dynamic reconstruction of a nanostructured conducting network.Nat Nanotechnol2018;13:1057-65

[168] Li Y,Wu M.Polyelectrolyte multilayers impart healability to highly electrically conductive films.Adv Mater2012;24:4578-82

[169] Zhao Z,Lee T,Xiang D.Smart eutectic gallium-indium: from properties to applications.Adv Mater2023;35:e2203391

[170] Chen S,Chan H.Liquid metal functionalization innovations in wearables and soft robotics for smart healthcare applications.Adv Funct Mater2023;2309989

[171] Xu C,Yuan S,Liu H.High-resolution patterning of liquid metal on hydrogel for flexible, stretchable, and self-healing electronics.Adv Elect Mater2020;6:1900721

[172] Guo R,Yuan B,Liu J.Magnetic liquid metal (Fe-EGaIn) based multifunctional electronics for remote self-healing materials, degradable electronics, and thermal transfer printing.Adv Sci2019;6:1901478 PMCID:PMC6794621

[173] Yun G,Sun S.Liquid metal-filled magnetorheological elastomer with positive piezoconductivity.Nat Commun2019;10:1300 PMCID:PMC6428896

[174] Markvicka EJ,Huang X.An autonomously electrically self-healing liquid metal-elastomer composite for robust soft-matter robotics and electronics.Nat Mater2018;17:618-24

[175] Wang M,Ning L.Liquid metal and Mxene enable self-healing soft electronics based on double networks of bacterial cellulose hydrogels.Carbohydr Polym2023;301:120330

[176] Chu K,Yang H.Smart passivation materials with a liquid metal microcapsule as self-healing conductors for sustainable and flexible perovskite solar cells.Adv Funct Mater2018;28:1800110

[177] Blaiszik BJ,Grady ME.Autonomic restoration of electrical conductivity.Adv Mater2012;24:398-401

[178] Dickey MD,Larsen RJ,Weitz DA.Eutectic gallium-indium (EGaIn): a liquid metal alloy for the formation of stable structures in microchannels at room temperature.Adv Funct Mater2008;18:1097-104

[179] Krisnadi F,Ankit .Directed assembly of liquid metal-elastomer conductors for stretchable and self-healing electronics.Adv Mater2020;32:e2001642

[180] Park S,Parida K,Lee PS.A stretchable and self-healing energy storage device based on mechanically and electrically restorative liquid-metal particles and carboxylated polyurethane composites.Adv Mater2019;31:e1805536

[181] Shi C,Lei Z,Zhang W.Heterogeneous integration of rigid, soft, and liquid materials for self-healable, recyclable, and reconfigurable wearable electronics.Sci Adv2020;6:eabd0202 PMCID:PMC7673720

[182] Ren X,Jiang J.Fire-retardant and thermal-insulating cellulose nanofibril aerogel modified by in situ supramolecular assembly of melamine and phytic acid.Adv Eng Mater2022;24:2101534

[183] Wang Y,Cheng F.Ti₃C₂T_x MXene-based flexible piezoresistive physical sensors.ACS Nano2022;16:1734-58

[184] Sun X,Yu Z,Jiang F.A biomimetic “salting out-alignment-locking” tactic to design strong and tough hydrogel.Adv Mater2024;:e2400084

[185] Mu C,Mei D.Development of robotic hand tactile sensing system for distributed contact force sensing in robotic dexterous multimodal grasping.Int J Intell Robot Appl2022;6:760-72

[186] Deng C,Liu L,Li M.Self-powered insole plantar pressure mapping system.Adv Funct Mater2018;28:1801606

[187] Tu J,Li W.Electronic skins with multimodal sensing and perception.Soft Sci2023;3:25

[188] Jeon S,Trung TQ,Lee N.Flexible multimodal sensors for electronic skin: principle, materials, device, array architecture, and data acquisition method.Proc IEEE2019;107:2065-83

[189] Won SM,Kim BH.Multimodal sensing with a three-dimensional piezoresistive structure.ACS Nano2019;13:10972-9

[190] Wang C,Zhang M,Zhang Y.An all-silk-derived dual-mode e-skin for simultaneous temperature-pressure detection.ACS Appl Mater Interfaces2017;9:39484-92

[191] Lou Z,Wang L.Ultrasensitive and ultraflexible e-skins with dual functionalities for wearable electronics.Nano Energy2017;38:28-35

[192] Yang R,Tiwari N,Li T.Multimodal sensors with decoupled sensing mechanisms.Adv Sci2022;9:e2202470 PMCID:PMC9475538

[193] Peng S,Yu Y,Lovell NH.Multimodal capacitive and piezoresistive sensor for simultaneous measurement of multiple forces.ACS Appl Mater Interfaces2020;12:22179-90

[194] Ho DH,Kim SY,Kim DH.Stretchable and multimodal all graphene electronic skin.Adv Mater2016;28:2601-8

[195] Zhao XF,Sun P.Spider web-like flexible tactile sensor for pressure-strain simultaneous detection.ACS Appl Mater Interfaces2021;13:10428-36

[196] Hua Q,Liu H.Skin-inspired highly stretchable and conformable matrix networks for multifunctional sensing.Nat Commun2018;9:244 PMCID:PMC5770430

[197] Lin W,Peng G,Hu H.Skin-inspired piezoelectric tactile sensor array with crosstalk-free row+column electrodes for spatiotemporally distinguishing diverse stimuli.Adv Sci2021;8:2002817 PMCID:PMC7856889

[198] Shin J,Kim J.Sensitive wearable temperature sensor with seamless monolithic integration.Adv Mater2020;32:e1905527

[199] Zhang J,Zhang L,Lu A.Transparent, ultra-stretching, tough, adhesive carboxyethyl chitin/polyacrylamide hydrogel toward high-performance soft electronics.Nanomicro Lett2022;15:8 PMCID:PMC9729505

[200] Wang X,Zhao C.Bionic-leaf vein inspired breathable anti-impact wearable electronics with health monitoring, electromagnetic interference shielding and thermal management.J Mater Sci Technol2024;188:216-27

[201] Liu C,Wang Y.Machine-learning-based calibration of temperature sensors.Sensors2023;23:7347 PMCID:PMC10490205

[202] Wang M,Luo Y.Fusing stretchable sensing technology with machine learning for human-machine interfaces.Adv Funct Mater2021;31:2008807

[203] Xu C,Sempionatto JR.A physicochemical-sensing electronic skin for stress response monitoring.Nat Electron2024;7:168-79 PMCID:PMC10906959

[204] Pyun KR,Yoo MJ.Machine-learned wearable sensors for real-time hand-motion recognition: toward practical applications.Natl Sci Rev2024;11:nwad298 PMCID:PMC10776364

[205] Xu C,Gao W.Artificial intelligence-powered electronic skin.Nat Mach Intell2023;5:1344-55 PMCID:PMC10868719

[206] Huang Q,Duan Z.Electrochemical self-powered strain sensor for static and dynamic strain detections.Nano Energy2023;118:108997

[207] Dawar N.Action detection and recognition in continuous action streams by deep learning-based sensing fusion.IEEE Sensors J2018;18:9660-8

[208] Shen L,Lu L.Domain-engineered flexible ferrite membrane for novel machine learning based multimodal flexible sensing.Adv Mater Inter2022;9:2101989

[209] Li N,Yang X.Deep-learning-assisted thermogalvanic hydrogel e-skin for self-powered signature recognition and biometric authentication.Adv Funct Mater2024;34:2314419

[210] Wang L,Qi X.Personal protective gloves with objects recognizing for rescuing in disaster.Chem Eng J2023;477:146986

[211] Niu H,Zhang Q,Kim NY.Intuition-and-tactile bimodal sensing based on artificial-intelligence-motivated all-fabric bionic electronic skin for intelligent material perception.Small2024;20:e2308127

[212] Kim KK,Kim M.A deep-learned skin sensor decoding the epicentral human motions.Nat Commun2020;11:2149 PMCID:PMC7195472

[213] Tan H,Tao Q,van Dijken S.Bioinspired multisensory neural network with crossmodal integration and recognition.Nat Commun2021;12:1120 PMCID:PMC7893014

[214] Bai Z,Zheng M.Mechanically robust and transparent organohydrogel-based e-skin nanoengineered from natural skin.Adv Funct Mater2023;33:2212856

[215] Gao Q,Li Y.Biological tissue-inspired ultrasoft, ultrathin, and mechanically enhanced microfiber composite hydrogel for flexible bioelectronics.Nanomicro Lett2023;15:139 PMCID:PMC10225432

[216] Sun X,Zhu J,Servati P.Tough and ultrastretchable liquid-free ion conductor strengthened by deep eutectic solvent hydrolyzed cellulose microfibers.Adv Funct Mater2022;32:2202533

[217] Cho S,Park H.Wireless, multimodal sensors for continuous measurement of pressure, temperature, and hydration of patients in wheelchair.npj Flex Electron2023;7:8

[218] Yin F,Kim E,Li Y.Advanced polymer materials-based electronic skins for tactile and non-contact sensing applications.InfoMat2023;5:e12424

[219] Beker L,You I.A bioinspired stretchable membrane-based compliance sensor.Proc Natl Acad Sci U S A2020;117:11314-20 PMCID:PMC7260970

[220] Tao K,Yu J.Ultra-sensitive, deformable, and transparent triboelectric tactile sensor based on micro-pyramid patterned ionic hydrogel for interactive human-machine interfaces.Adv Sci2022;9:e2104168 PMCID:PMC8981453

[221] Boutry CM,Jorda M.A hierarchically patterned, bioinspired e-skin able to detect the direction of applied pressure for robotics.Sci Robot2018;3:eaau6914

[222] Zhu L,Mei D.Large-area hand-covering elastomeric electronic skin sensor with distributed multifunctional sensing capability.Adv Intell Syst2022;4:2100118

[223] Zhang C,Huang X,Li Y.A stretchable dual-mode sensor array for multifunctional robotic electronic skin.Nano Energy2019;62:164-70

[224] Zhang L,Liao Y.A self-protective, reproducible textile sensor with high performance towards human-machine interactions.J Mater Chem A2019;7:26631-40

[225] Lu C,Shen Y.Skin-like transparent, high resilience, low hysteresis, fatigue-resistant cellulose-based eutectogel for self-powered e-skin and human-machine interaction.Adv Funct Mater2024;34:2311502

[226] Liu W,Mei D.A flexible dual-mode capacitive sensor for highly sensitive touchless and tactile sensing in human-machine interactions.Adv Mater Technol2024;9:2301685

[227] Osborn LE,Betthauser JL.Prosthesis with neuromorphic multilayered e-dermis perceives touch and pain.Sci Robot2018;3:10 PMCID:PMC7051004

[228] Yang M,Yue Y.High-performance flexible pressure sensor with a self-healing function for tactile feedback.Adv Sci2022;9:e2200507 PMCID:PMC9284154

[229] Luo S,Tang X.Microconformal electrode-dielectric integration for flexible ultrasensitive robotic tactile sensing.Nano Energy2021;80:105580

[230] Yang JY,Shaikh MO.Biocompatible, antibacterial, and stable deep eutectic solvent-based ionic gel multimodal sensors for healthcare applications.ACS Appl Mater Interfaces2023;15:55244-57

[231] Peng Z,Zhang X.Advancing the pressure sensing performance and biocompatible of conductive rGO/PEDOT/PDMS composite film for simple and efficient pressure sensor.Smart Mater Struct2023;32:125020

[232] Wan S,Yin K.A highly skin-conformal and biodegradable graphene-based strain sensor.Small Methods2018;2:1700374

[233] Wang Y,Lu A.Highly stretchable, transparent cellulose/PVA composite hydrogel for multiple sensing and triboelectric nanogenerators.J Mater Chem A2020;8:13935-41

[234] Wang C,Yu Z.User-interactive electronic skin for instantaneous pressure visualization.Nat Mater2013;12:899-904

[235] Zhang Z,Jia S.Body-conformable light-emitting materials and devices.Nat Photon2024;18:114-26

[236] Cheng Y,Meredith CH.Photoluminescent humidity sensors based on droplet-enabled porous composite gels.ACS Mater Lett2023;5:2074-83

[237] Tan D,Chung KY.Self-adhesive, detach-on-demand, and waterproof hydrophobic electronic skins with customized functionality and wearability.Adv Funct Mater2024;34:2311457

[238] Lin J,Liu Z.Anti-liquid-interfering and bacterially antiadhesive strategy for highly stretchable and ultrasensitive strain sensors based on cassie-baxter wetting state.Adv Funct Mater2020;30:2000398

[239] Pan X,Guo R.An integrated transparent, UV-filtering organohydrogel sensor via molecular-level ion conductive channels.J Mater Chem A2019;7:4525-35

[240] Cai J,Chen X.Multifunctional polydimethylsiloxane foam with multi-walled carbon nanotube and thermo-expandable microsphere for temperature sensing, microwave shielding and piezoresistive sensor.Chem Eng J2020;393:124805

[241] Wei W,Song J,Li J.Tunable graphene/nitrocellulose temperature alarm sensors.ACS Appl Mater Interfaces2022;14:13790-800 PMCID:PMC9098115

[242] Tan D.Advanced interfacial design for electronic skins with customizable functionalities and wearability.Adv Funct Mater2023;33:2306793

[243] Huang C.Facile fabrication of a stretchable and flexible nanofiber carbon film-sensing electrode by electrospinning and its application in smart clothing for ECG and EMG monitoring.ACS Appl Electron Mater2021;3:676-86

[244] Li C.Progress in the brain-computer interface: an interview with Bin He.Natl Sci Rev2020;7:480-3 PMCID:PMC8288869

[245] Venkatesh, Kavya, Keerthi R, Ikshu B, Badarish IT. Neuralink and brain control machine. IJARSCT 2022;2. Available from: https://ijarsct.co.in/Paper3135.pdf. [Last accessed on 7 May 2024]