Tattoo-like epidermal electronics as skin sensors for human-machine interfaces

Abstract

Flexible electronic skin (e-skin) has been successfully utilized in diverse applications, including prosthesis sensing, body-motion monitoring and human-machine interfaces, due to its excellent mechanical properties and electrical characteristics. However, current e-skins are still relatively thick (> 10 µm) and uncomfortable for long-term usage on the human body. Herein, an ultrathin skin-integrated strain sensor with miniaturized dimensions, based on the piezoresistive effect, with excellent stability and robustness, is introduced. The fractal curve-shaped Au electrode in a serpentine format, which is the dominant component of the strain sensor, is sensitive to ambient strain variations and can turn the mechanical motion into a stable electrical signal output. With the advanced design of metallic electrodes, the device presents good operational stability and excellent mechanical tolerance towards bending, stretching and twisting. The stain sensor allows intimate mounting onto the human epidermal surface for the detection of body motion. By adopting a liquid bandage as an encapsulation layer, the device exhibits an ultrathin thickness (6.2 µm), high sensitivity towards mechanical deformations and capability for the clear detection of motion, such as walking, finger bending and the human pulse rate with identifiable electrical signals. Furthermore, the tattoo-like strain sensor is applied in robotic control by tracing finger bending motion and results in the smooth control of a robotic hand nearly without any detention. This e-skin design exhibits excellent potential for wearable electronics and human-machine interfaces.

Keywords

Skin-integrated electronics / ultrathin / excellent repeatability / fractal design / stretchable electronics

References

[1] Yeo WH,Lee J.Multifunctional epidermal electronics printed directly onto the skin.Adv Mater2013;25:2773-8

[2] Jeong JW,Akhtar A.Materials and optimized designs for human-machine interfaces via epidermal electronics.Adv Mater2013;25:6839-46

[3] Zhu Z,Pan T.Imperceptible epidermal-iontronic interface for wearable sensing.Adv Mater2018;30:1705122

[4] Liu Y,Qazi R.Epidermal mechano-acoustic sensing electronics for cardiovascular diagnostics and human-machine interfaces.Sci Adv2016;2:e1601185 PMCID:PMC5262452

[5] Reeder JT,Xue Y.Waterproof, electronics-enabled, epidermal microfluidic devices for sweat collection, biomarker analysis, and thermography in aquatic settings.Sci Adv2019;5:eaau6356 PMCID:PMC6357724

[6] Yu X,Yu Y.Skin-integrated wireless haptic interfaces for virtual and augmented reality.Nature2019;575:473-9

[7] Yeo JC, Lim CT. Emerging flexible and wearable physical sensing platforms for healthcare and biomedical applications.Microsyst Nanoeng2016;2:16043 PMCID:PMC6444731

[8] Liu Y,Avila R.Epidermal electronics for respiration monitoring via thermo-sensitive measuring.Materials Today Physics2020;13:100199

[9] Kim CH,Youn J,Jeong J.Simple and cost-effective microfabrication of flexible and stretchable electronics for wearable multi-functional electrophysiological monitoring.Sci Rep2021;11:14823 PMCID:PMC8292344

[10] Guo J,Zhang D,Zhao Y.Morphological hydrogel microfibers with MXene encapsulation for electronic skin.Research (Wash D C)2021;2021:7065907 PMCID:PMC7953990

[11] Liu Y,Wang L.Skin-integrated graphene-embedded lead zirconate titanate rubber for energy harvesting and mechanical sensing.Adv Mater Technol2019;4:1900744

[12] Tzou H.Distributed piezoelectric sensor/actuator design for dynamic measurement/control of distributed parameter systems: a piezoelectric finite element approach.J Sound Vib1990;138:17-34

[13] Ng TH.Sensitivity analysis and energy harvesting for a self-powered piezoelectric sensor.J Intell Mater Syst Struct2005;16:785-97

[14] Liu Y,Zhao L.Electronic skin from high-throughput fabrication of intrinsically stretchable lead zirconate titanate elastomer.Research (Wash D C)2020;2020:1085417 PMCID:PMC7586250

[15] Wang X,Dong L.Self-powered high-resolution and pressure-sensitive triboelectric sensor matrix for real-time tactile mapping.Adv Mater2016;28:2896-903

[16] An T,Gong S.Self-powered gold nanowire tattoo triboelectric sensors for soft wearable human-machine interface.Nano Energy2020;77:105295

[17] Wu M,Yao K.Thin, soft, skin-integrated foam-based triboelectric nanogenerators for tactile sensing and energy harvesting.Materials Today Energy2021;20:100657

[18] Yiu C,Liu Y.Skin-like strain sensors enabled by elastomer composites for human-machine interfaces.Coatings2020;10:711

[19] Yan C,Kang W.Highly stretchable piezoresistive graphene-nanocellulose nanopaper for strain sensors.Adv Mater2014;26:2022-7

[20] Pacelli M,Paradiso R.Textile piezoresistive sensors for biomechanical variables monitoring.Conf Proc IEEE Eng Med Biol Soc2006;2006:5358-61

[21] Hu N, Fukunaga H, Atobe S, Liu Y, Li J. Piezoresistive strain sensors made from carbon nanotubes based polymer nanocomposites.Sensors (Basel)2011;11:10691-723 PMCID:PMC3274309

[22] Zhu J,Zhang M.Recent progress in flexible tactile sensor systems: from design to application.Soft Sci2021;1:3

[23] Liu Y,Zhao L,Zi Y.Recent progress on flexible nanogenerators toward self-powered systems.InfoMat2020;2:318-40

[24] Wang L,Liu Q.A metal-electrode-free, fully integrated, soft triboelectric sensor array for self-powered tactile sensing.Microsyst Nanoeng2020;6:59 PMCID:PMC8433331

[25] Zhou Y,Wang H.Highly sensitive, self-powered and wearable electronic skin based on pressure-sensitive nanofiber woven fabric sensor.Sci Rep2017;7:12949 PMCID:PMC5636882

[26] Lou Z,Wang L.Recent progress of self-powered sensing systems for wearable electronics.Small2017;13:1701791

[27] Wang Y,Yang Y.Graphene-polymer nanocomposite-based redox-induced electricity for flexible self-powered strain sensors.Adv Energy Mater2018;8:1800961

[28] Lu Y,Guo Z,Wujcik EK.Recent developments in bio-monitoring via advanced polymer nanocomposite-based wearable strain sensors.Biosens Bioelectron2019;123:167-77

[29] Wang X,Zhang X.A highly stretchable transparent self-powered triboelectric tactile sensor with metallized nanofibers for wearable electronics.Adv Mater2018;30:e1706738

[30] Zhao G,Shi N.Transparent and stretchable triboelectric nanogenerator for self-powered tactile sensing.Nano Energy2019;59:302-10

[31] Yang M,Liu D.A Fully Self-healing piezoelectric nanogenerator for self-powered pressure sensing electronic skin.Research (Wash D C)2021;2021:9793458 PMCID:PMC8063864

[32] Shu YC.Analysis of power output for piezoelectric energy harvesting systems.Smart Mater Struct2006;15:1499-512

[33] Feng W,Gao F.Sensitive electronic-skin strain sensor array based on the patterned two-dimensional α-In₂Se₃.Chem Mater2016;28:4278-83

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

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

[36] Cheng Y,Zhai H.Stretchable electronic skin based on silver nanowire composite fiber electrodes for sensing pressure, proximity, and multidirectional strain.Nanoscale2017;9:3834-42

[37] Kanao K,Yamamoto Y.Highly selective flexible tactile strain and temperature sensors against substrate bending for an artificial skin.RSC Adv2015;5:30170-4

[38] Gong S,Su B.Highly stretchy black gold e-skin nanopatches as highly sensitive wearable biomedical sensors.Adv Electron Mater2015;1:1400063

[39] Luo N,Liu J,Wong CP.Hollow-structured graphene-silicone-composite-based piezoresistive sensors: decoupled property tuning and bending reliability.Adv Mater2017;29:1702675

[40] Chen H,Su Z.Fingertip-inspired electronic skin based on triboelectric sliding sensing and porous piezoresistive pressure detection.Nano Energy2017;40:65-72

[41] Niu D,Ye G.Graphene-elastomer nanocomposites based flexible piezoresistive sensors for strain and pressure detection.Materials Research Bulletin2018;102:92-9

[42] Canavese G,Stassi S.Comprehensive characterization of large piezoresistive variation of Ni-PDMS composites.AMM2011;110-116:1336-44

[43] Cai G,Qian K,Li S.Extremely stretchable strain sensors based on conductive self-healing dynamic cross-links hydrogels for human-motion detection.Adv Sci (Weinh)2017;4:1600190 PMCID:PMC5323873

[44] Jing X,Peng X.Biocompatible, self-healing, highly stretchable polyacrylic acid/reduced graphene oxide nanocomposite hydrogel sensors via mussel-inspired chemistry.Carbon2018;136:63-72

[45] Liu S.Ultrastretchable and self-healing double-network hydrogel for 3D printing and strain sensor.ACS Appl Mater Interfaces2017;9:26429-37

[46] Yin F,Peng H.Flexible and highly sensitive artificial electronic skin based on graphene/polyamide interlocking fabric.J Mater Chem C2018;6:6840-6

[47] Zhao L,Dai SW.Construction of sandwich-like porous structure of graphene-coated foam composites for ultrasensitive and flexible pressure sensors.Nanoscale2019;11:10229-38

[48] Nie P,Xu X.High-performance piezoresistive electronic skin with bionic hierarchical microstructure and microcracks.ACS Appl Mater Interfaces2017;9:14911-9

[49] Hsu MS,Lee CY.Gold nanostructures on flexible substrates as electrochemical dopamine sensors.ACS Appl Mater Interfaces2012;4:5570-5

[50] Zhu Y.Highly bendable and stretchable electrodes based on micro/nanostructured gold films for flexible sensors and electronics.Adv Electron Mater2016;2:1500345

[51] Li YQ,Zhu WB,Hu N.Flexible wire-shaped strain sensor from cotton thread for human health and motion detection.Sci Rep2017;7:45013 PMCID:PMC5359581

[52] Sankar V,Bhat VN.Waterproof flexible polymer-functionalized graphene-based piezoresistive strain sensor for structural health monitoring and wearable devices.ACS Omega2020;5:12682-91 PMCID:PMC7288371

[53] Wang X,Song H,Gou J.Highly Stretchable And Wearable Strain Sensor Based On Printable Carbon Nanotube Layers/Polydimethylsiloxane Composites With Adjustable Sensitivity.ACS Appl Mater Interfaces2018;10:7371-80

[54] Zheng Y,Zhou Y.High-performance wearable strain sensor based on graphene/cotton fabric with high durability and low detection limit.ACS Appl Mater Interfaces2020;12:1474-85

[55] Zheng S,Huang Y.Highly sensitive and multifunctional piezoresistive sensor based on polyaniline foam for wearable Human-Activity monitoring.Composites Part A: Applied Science and Manufacturing2019;121:510-6

[56] Zhang C,Rao W,Xu W.A simple method of fabricating nickel-coated cotton fabrics for wearable strain sensor.Cellulose2018;25:4859-70