Recent progress in flexible capacitive sensors: Structures and properties

Ling, 2020, Disruptive, soft, wearable sensors, Adv. Mater., 32, 10.1002/adma.201904664 Kenry, 2016, Emerging flexible and wearable physical sensing platforms for healthcare and biomedical applications, Microsyst Nanoeng, 2, 16043, 10.1038/micronano.2016.43 Xie, 2019, Flexible multifunctional sensors for wearable and robotic applications, Adv. Mater. Technol., 4, 10.1002/admt.201800626 Dong, 2020, Wearable triboelectric-human-machine interface (THMI) using robust nanophotonic readout, ACS Nano, 14, 8915, 10.1021/acsnano.0c03728 Takamatsu, 2016, Wearable keyboard using conducting polymer electrodes on textiles, Adv. Mater., 28, 4485, 10.1002/adma.201504249 Lee, 2015, Conductive fiber-based ultrasensitive textile pressure sensor for wearable electronics, Adv. Mater., 27, 2433, 10.1002/adma.201500009 Wang, 2015, Recent progress in electronic skin, Adv. Sci., 2, 1500169, 10.1002/advs.201500169 Canavese, 2014, Piezoresistive flexible composite for robotic tactile applications, Sensor Actuator Phys., 208, 1, 10.1016/j.sna.2013.11.018 Luo, 2016, Flexible piezoresistive sensor patch enabling ultralow power cuffless blood pressure measurement, Adv. Funct. Mater., 26, 1178, 10.1002/adfm.201504560 Kim, 2018, Transparent, flexible, conformal capacitive pressure sensors with nanoparticles, Small, 14, 10.1002/smll.201870032 Kumar, 2020, RTV silicone rubber composites reinforced with carbon nanotubes, titanium-di-oxide and their hybrid: mechanical and piezoelectric actuation performance, Nano Mater. Sci. Zhu, 2019, Self-Powered and self-functional cotton sock using piezoelectric and triboelectric hybrid mechanism for healthcare and sports monitoring, ACS Nano, 13, 1940 Chen, 2020, Progress in achieving high-performance piezoresistive and capacitive flexible pressure sensors: a review, J. Mater. Sci. Technol., 43, 175, 10.1016/j.jmst.2019.11.010 Das, 2019, A laser ablated graphene-based flexible self-powered pressure sensor for human gestures and finger pulse monitoring, Nano Res., 12, 1789, 10.1007/s12274-019-2433-5 Wang, 2021, Core-shell structured silk Fibroin/PVDF piezoelectric nanofibers for energy harvesting and self-powered sensing, Nano Mater. Sci. Kong, 2021, SnO2 nanostructured materials used as gas sensors for the detection of hazardous and flammable gases: a review, Nano Mater. Sci. Shi, 2020, Progress in wearable electronics/photonics—moving toward the era of artificial intelligence and internet of things, InfoMat, 2, 1131, 10.1002/inf2.12122 Wang, 2017, Flexible sensing electronics for wearable/attachable health monitoring, Small, 13 Lai, 2017, Single-thread-based wearable and highly stretchable triboelectric nanogenerators and their applications in cloth-based self-powered human-interactive and biomedical sensing, Adv. Funct. Mater., 27, 10.1002/adfm.201604462 In, 2015, Exo-glove: a wearable robot for the hand with a soft tendon routing system, IEEE Robot. Autom. Mag., 22, 97, 10.1109/MRA.2014.2362863 Yao, 2021, Augmented reality interfaces using virtual customization of microstructured electronic skin sensor sensitivity performances, Adv. Funct. Mater., 10.1002/adfm.202008650 Yeom, 2015, Large-area compliant tactile sensors using printed carbon nanotube active-matrix backplanes, Adv. Mater., 27, 1561, 10.1002/adma.201404850 Yeo, 2017, Wearable mechanotransduced tactile sensor for haptic perception, Adv. Mater. Technol., 2, 10.1002/admt.201700006 Lipomi, 2011, Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes, Nat. Nanotechnol., 6, 788, 10.1038/nnano.2011.184 Mannsfeld, 2010, Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers, Nat. Mater., 9, 859, 10.1038/nmat2834 Liu, 2020, Highly transparent and flexible iontronic pressure sensors based on an opaque to transparent transition, Adv. Sci., 7, 2000348, 10.1002/advs.202000348 Sun, 2014, Ionic skin, Adv. Mater., 26, 7608, 10.1002/adma.201403441 Pang, 2015, Highly skin-conformal microhairy sensor for pulse signal amplification, Adv. Mater., 27, 634, 10.1002/adma.201403807 Guo, 2019, Anodized aluminum oxide-assisted low-cost flexible capacitive pressure sensors based on double-sided nanopillars by a facile fabrication method, ACS Appl. Mater. Interfaces, 11, 48594, 10.1021/acsami.9b17966 Moheimani, 2021, Thermoplastic polyurethane flexible capacitive proximity sensor reinforced by CNTs for applications in the creative industries, Sci. Rep., 11, 1104, 10.1038/s41598-020-80071-0 Zhang Fassler, 2013, Soft-matter capacitors and inductors for hyperelastic strain sensing and stretchable electronics, Smart Mater. Struct., 22 Choi, 2020, Synergetic effect of porous elastomer and percolation of carbon nanotube filler toward high performance capacitive pressure sensors, ACS Appl. Mater. Interfaces, 12, 1698, 10.1021/acsami.9b20097 Cotton, 2009, A multifunctional capacitive sensor for stretchable electronic skins, IEEE Sensor. J., 9, 2008, 10.1109/JSEN.2009.2030709 Jin, 2017, Stretchable dual-capacitor multi-sensor for touch-curvature-pressure-strain sensing, Sci. Rep., 7, 10854, 10.1038/s41598-017-11217-w Cohen, 2012, A highly elastic, capacitive strain gauge based on percolating nanotube networks, Nano Lett., 12, 1821, 10.1021/nl204052z Yuan, 2018, Giant electrostriction of soft nanocomposites based on liquid crystalline graphene, ACS Nano, 12, 1688, 10.1021/acsnano.7b08332 Charaya, 2019, Thermochromic and piezocapacitive flexible sensor array by combining composite elastomer dielectrics and transparent ionic hydrogel electrodes, Adv. Mater. Technol., 4, 10.1002/admt.201900327 Beker, 2020, A bioinspired stretchable membrane-based compliance sensor, Proc. Natl. Acad. Sci. U. S. A., 117, 11314, 10.1073/pnas.1909532117 Liu, 2019, Polyelectrolyte dielectrics for flexible low-voltage organic thin-film transistors in highly sensitive pressure sensing, Adv. Funct. Mater., 29 Chunyan, 2008, Flexible dome and bump shape piezoelectric tactile sensors using PVDF-TrFE copolymer, J. Microelectromech. Syst., 17, 334, 10.1109/JMEMS.2007.911375 Dobrzynska, 2012, Flexible polyimide-based force sensor, Sensor Actuator Phys., 173, 127, 10.1016/j.sna.2011.11.006 Yin, 2019, Micropatterned elastic ionic polyacrylamide hydrogel for low-voltage capacitive and organic thin-film transistor pressure sensors, Nano Energy, 58, 96, 10.1016/j.nanoen.2019.01.032 Bian, 2018, Stretchable 3D polymer for simultaneously mechanical energy harvesting and biomimetic force sensing, Nano Energy, 47, 442, 10.1016/j.nanoen.2018.03.027 Amit, 2019, Point-of-use robotic sensors for simultaneous pressure detection and chemical analysis, Mater. Horiz., 6, 604, 10.1039/C8MH01412D Choong, 2014, Highly stretchable resistive pressure sensors using a conductive elastomeric composite on a micropyramid array, Adv. Mater., 26, 3451, 10.1002/adma.201305182 Ruth, 2020, Microengineering pressure sensor active layers for improved performance, Adv. Funct. Mater., 30, 10.1002/adfm.202003491 Jiang, 2020, Sandwich structured dielectrics for air-stable and flexible low-voltage organic transistors in ultrasensitive pressure sensing, Mater. Chem. Front., 4, 1459, 10.1039/D0QM00062K Tee, 2014, Tunable flexible pressure sensors using microstructured elastomer geometries for intuitive electronics, Adv. Funct. Mater., 24, 5427, 10.1002/adfm.201400712 Ruth, 2019, Rational design of capacitive pressure sensors based on pyramidal microstructures for specialized monitoring of biosignals, Adv. Funct. Mater., 30 Yin, 2018, Solution-processed bilayer dielectrics for flexible low-voltage organic field-effect transistors in pressure-sensing applications, Adv. Sci., 5, 1701041, 10.1002/advs.201701041 Elsayes, 2020, Plant-based biodegradable capacitive tactile pressure sensor using flexible and transparent leaf skeletons as electrodes and flower petal as dielectric layer, Adv. Sustain. Syst., 4, 10.1002/adsu.202000056 Koo, 2018, Flexible and stretchable smart display: materials, fabrication, device design, and system integration, Adv. Funct. Mater., 28, 10.1002/adfm.201801834 Nassar, 2016, Paper skin multisensory platform for simultaneous environmental monitoring, Adv. Mater. Technol., 1, 10.1002/admt.201600004 Nassar, 2017, Impact of physical deformation on electrical performance of paper-based sensors, IEEE Trans. Electron. Dev., 64, 2022, 10.1109/TED.2017.2650981 Wang, 2014, Silk-molded flexible, ultrasensitive, and highly stable electronic skin for monitoring human physiological signals, Adv. Mater., 26, 1336, 10.1002/adma.201304248 Dagdeviren, 2014, Conformable amplified lead zirconate titanate sensors with enhanced piezoelectric response for cutaneous pressure monitoring, Nat. Commun., 5, 4496, 10.1038/ncomms5496 Kaltenbrunner, 2013, An ultra-lightweight design for imperceptible plastic electronics, Nature, 499, 458, 10.1038/nature12314 Hammock, 2013, 25th anniversary article: the evolution of electronic skin (e-skin): a brief history, design considerations, and recent progress, Adv. Mater., 25, 5997, 10.1002/adma.201302240 Sekitani, 2010, Flexible organic transistors and circuits with extreme bending stability, Nat. Mater., 9, 1015, 10.1038/nmat2896 Yeo, 2013, Multifunctional epidermal electronics printed directly onto the skin, Adv. Mater., 25, 2773, 10.1002/adma.201204426 Takahashi, 2011, Carbon nanotube active-matrix backplanes for conformal electronics and sensors, Nano Lett., 11, 5408, 10.1021/nl203117h Cao, 2021, Thermoelectric PEDOT:PSS Sheet/SWCNTs composites films with layered structure, Compos. Commun., 27, 10.1016/j.coco.2021.100869 Schwartz, 2013, Flexible polymer transistors with high pressure sensitivity for application in electronic skin and health monitoring, Nat. Commun., 4, 1859, 10.1038/ncomms2832 Chhetry, 2017, A flexible and highly sensitive capacitive pressure sensor based on conductive fibers with a microporous dielectric for wearable electronics, J. Mater. Chem. C, 5, 10068, 10.1039/C7TC02926H Zeng, 2019, Tunable, ultrasensitive, and flexible pressure sensors based on wrinkled microstructures for electronic skins, ACS Appl. Mater. Interfaces, 11, 21218, 10.1021/acsami.9b02518 Yang, 2019, Microstructured porous pyramid-based ultrahigh sensitive pressure sensor insensitive to strain and temperature, ACS Appl. Mater. Interfaces, 11, 19472, 10.1021/acsami.9b03261 Ankit, 2020, High-k, ultrastretchable self-enclosed ionic liquid-elastomer composites for soft robotics and flexible electronics, ACS Appl. Mater. Interfaces, 12, 37561, 10.1021/acsami.0c08754 Pan, 2021, The ferroelectric ceramic/elastomer composite as the dielectric coating of soft capacitive neural interface: the competitive effects of ceramic particles, Compos. B Eng., 204 Kim, 2019, Soft wearable pressure sensors for beat-to-beat blood pressure monitoring, Adv. Healthc. Mater., 8, 10.1002/adhm.201900109 Wan, 2017, Graphene oxide as high-performance dielectric materials for capacitive pressure sensors, Carbon, 114, 209, 10.1016/j.carbon.2016.12.023 Kweon, 2019, Stretchable and self-healable conductive hydrogels for wearable multimodal touch sensors with thermoresponsive behavior, ACS Appl. Mater. Interfaces, 11, 26134, 10.1021/acsami.9b04440 Fu, 2020, A highly sensitive, reliable, and high-temperature-resistant flexible pressure sensor based on ceramic nanofibers, Adv. Sci., 7, 2000258, 10.1002/advs.202000258 Lee, 2018, Electroluminescent pressure-sensing displays, ACS Appl. Mater. Interfaces, 10, 13757, 10.1021/acsami.8b01790 Ho, 2019, Multifunctional smart textronics with blow-spun nonwoven fabrics, Adv. Funct. Mater., 29, 10.1002/adfm.201900025 Joo, 2015, Silver nanowire-embedded PDMS with a multiscale structure for a highly sensitive and robust flexible pressure sensor, Nanoscale, 7, 6208, 10.1039/C5NR00313J Li, 2016, Flexible capacitive tactile sensor based on micropatterned dielectric layer, Small, 12, 5042, 10.1002/smll.201600760 Wang, 2019, Conductive double-crosslinked network hydrogel with superior stretchability and self-healing ability, Mater. Res. Express, 6 Reynolds, 2020, Super-soft solvent-free bottlebrush elastomers for touch sensing, Mater. Horiz., 7, 181, 10.1039/C9MH00951E Chen, 2016, Large area one-step facile processing of microstructured elastomeric dielectric film for high sensitivity and durable sensing over wide pressure range, ACS Appl. Mater. Interfaces, 8, 20364, 10.1021/acsami.6b05177 Li, 2020, A porous and air gap elastomeric dielectric layer for wearable capacitive pressure sensor with high sensitivity and a wide detection range, J. Mater. Chem. C, 8, 11468, 10.1039/D0TC00443J Kim, 2018, Highly conformable, transparent electrodes for epidermal electronics, Nano Lett., 18, 4531, 10.1021/acs.nanolett.8b01743 Lei, 2017, A bioinspired mineral hydrogel as a self-healable, mechanically adaptable ionic skin for highly sensitive pressure sensing, Adv. Mater., 29, 10.1002/adma.201700321 Han, 2017, Photo-induced fabrication of Ag nanowire circuitry for invisible, ultrathin, conformable pressure sensors, J. Mater. Chem. C, 5, 9986, 10.1039/C7TC01423F Pierre Claver, 2021, Recent progress in flexible pressure sensors based electronic skin, Adv. Eng. Mater., 23, 10.1002/adem.202001187 Xiong, 2020, A flexible, ultra-highly sensitive and stable capacitive pressure sensor with convex microarrays for motion and health monitoring, Nano Energy, 70, 10.1016/j.nanoen.2019.104436 Bae, 2018, Pressure/temperature sensing bimodal electronic skin with stimulus discriminability and linear sensitivity, Adv. Mater., 30, 10.1002/adma.201803388 Wang, 2014, Broadband time-resolved elliptical crystal spectrometer for X-ray spectroscopic measurements in laser-produced plasmas, Chin. Phys. B, 23, 10.1088/1674-1056/23/11/113201 Wu, 2020, Rational design of flexible capacitive sensors with highly linear response over a broad pressure sensing range, Nanoscale, 12, 21198, 10.1039/D0NR06386J You, 2018, Stretchable capacitive fabric electronic skin woven by electrospun nanofiber coated yarns for detecting tactile and multimodal mechanical stimuli, J. Mater. Chem. C, 6, 12981, 10.1039/C8TC03631D Zhang, 2012, Development of a versatile capacitive tactile sensor based on transparent flexible materials integrating an excellent sensitivity and a high resolution, AIP Adv., 2, 10.1063/1.4706011 Yang, 2019, A flexible ionic liquid-polyurethane sponge capacitive pressure sensor, Sensor Actuator Phys., 285, 67, 10.1016/j.sna.2018.10.041 Park, 2018, Development of wearable and flexible insole type capacitive pressure sensor for continuous gait signal analysis, Org. Electron., 53, 213, 10.1016/j.orgel.2017.11.033 Guan, 2020, Silver nanowire-bacterial cellulose composite fiber-based sensor for highly sensitive detection of pressure and proximity, ACS Nano, 14, 15428, 10.1021/acsnano.0c06063 Chhetry, 2020, Enhanced sensitivity of capacitive pressure and strain sensor based on CaCu3Ti4O12 wrapped hybrid sponge for wearable applications, Adv. Funct. Mater., 30, 10.1002/adfm.201910020 Tay, 2020, Lightweight, superelastic boron nitride/polydimethylsiloxane foam as air dielectric substitute for multifunctional capacitive sensor applications, Adv. Funct. Mater., 30, 10.1002/adfm.201909604 Peng, 2020, Multimodal capacitive and piezoresistive sensor for simultaneous measurement of multiple forces, ACS Appl. Mater. Interfaces, 12, 22179, 10.1021/acsami.0c04448 Wang, 2019, Capacitive pressure sensor with wide-range, bendable, and high sensitivity based on the bionic komochi konbu structure and Cu/Ni nanofiber network, ACS Appl. Mater. Interfaces, 11, 11928, 10.1021/acsami.9b00941 Kim, 2019, Highly ordered 3D microstructure-based electronic skin capable of differentiating pressure, temperature, and proximity, ACS Appl. Mater. Interfaces, 11, 1503, 10.1021/acsami.8b19214 Li, 2017, Supercapacitive iontronic nanofabric sensing, Adv. Mater., 29, 10.1002/adma.201700253 Qin, 2021, Flexible and stretchable capacitive sensors with different microstructures, Adv. Mater., 33, 10.1002/adma.202008267 Mishra, 2021, Recent progress on flexible capacitive pressure sensors: from design and materials to applications, Adv. Mater. Technol., 6 Yoon, 2017, A novel means of fabricating microporous structures for the dielectric layers of capacitive pressure sensor, Microelectron. Eng., 179, 60, 10.1016/j.mee.2017.04.028 Zhou, 2021, Robust and sensitive pressure/strain sensors from solution processable composite hydrogels enhanced by hollow-structured conducting polymers, Chem. Eng. J., 403, 10.1016/j.cej.2020.126307 Alluri, 2017, Piezoelectric BaTiO 3/alginate spherical composite beads for energy harvesting and self-powered wearable flexion sensor, Compos. Sci. Technol., 142, 65, 10.1016/j.compscitech.2017.02.001 Liu, 2017, Large-area all-textile pressure sensors for monitoring human motion and physiological signals, Adv. Mater., 29, 10.1002/adma.201703700 Atalay, 2017, Batch fabrication of customizable silicone-textile composite capacitive strain sensors for human motion tracking, Adv. Mater. Technol., 2, 10.1002/admt.201700136 Zhang, 2020, Textile-only capacitive sensors with a lockstitch structure for facile integration in any areas of a fabric, ACS Sens., 5, 1535, 10.1021/acssensors.0c00210 Yan, 2021, Surface microstructure-controlled ZrO2 for highly sensitive room-temperature NO2 sensors, Nano Mater. Sci., 10.1016/j.nanoms.2021.02.001 Deng, 2016, Microstructure-based interfacial tuning mechanism of capacitive pressure sensors for electronic skin, J. Sens., 1 Pignanelli, 2019, A comparative analysis of capacitive-based flexible PDMS pressure sensors, Sensor Actuator Phys., 285, 427, 10.1016/j.sna.2018.11.014 Liu, 2018, Large dynamic range pressure sensor based on two semicircle-holes microstructured fiber, Sci. Rep., 8, 65, 10.1038/s41598-017-18245-6 Wan, 2018, A highly sensitive flexible capacitive tactile sensor with sparse and high-aspect-ratio microstructures, Adv. Electr. Mater., 4 Wan, 2018, Natural plant materials as dielectric layer for highly sensitive flexible electronic skin, Small, 14 Smith, 2019, Synthesis, properties, and applications of graphene oxide/reduced graphene oxide and their nanocomposites, Nano Mater. Sci., 1, 31, 10.1016/j.nanoms.2019.02.004 Ali, 2018, Pressure sensitive sensors based on carbon nanotubes, graphene, and its composites, J. Nanomater., 1 Park, 2018, Block copolymer structural color strain sensor, NPG Asia Mater., 10, 328, 10.1038/s41427-018-0036-3 Albanna, 2019, In situ bioprinting of autologous skin cells accelerates wound healing of extensive excisional full-thickness wounds, Sci. Rep., 9, 1856, 10.1038/s41598-018-38366-w Song, 2016, Wearable force touch sensor array using a flexible and transparent electrode, Adv. Funct. Mater., 27 Jin, 2020, Ultrathin nanofibrous membranes containing insulating microbeads for highly sensitive flexible pressure sensors, ACS Appl. Mater. Interfaces, 12, 13348, 10.1021/acsami.0c00448 Choi, 2020, Self-healable capacitive photodetectors with stretchability based on composite of ZnS:Cu particles and reversibly crosslinkable silicone elastomer, Adv. Mater. Technol., 5, 10.1002/admt.202000327 Cho, 2017, Micropatterned pyramidal ionic gels for sensing broad-range pressures with high sensitivity, ACS Appl. Mater. Interfaces, 9, 10128, 10.1021/acsami.7b00398 Nesser, 2018, Towards wireless highly sensitive capacitive strain sensors based on gold colloidal nanoparticles, Nanoscale, 10, 10479, 10.1039/C7NR09685B Wei, 2019, Flexible capacitive pressure sensor with sensitivity and linear measuring range enhanced based on porous composite of carbon conductive paste and polydimethylsiloxane, Nanotechnology, 30, 455501, 10.1088/1361-6528/ab3695 Hwang, 2019, A transparent stretchable sensor for distinguishable detection of touch and pressure by capacitive and piezoresistive signal transduction, NPG Asia Mater., 11, 10.1038/s41427-019-0126-x Zhang, 2020, Highly stretchable and sensitive pressure sensor array based on icicle-shaped liquid metal film electrodes, ACS Appl. Mater. Interfaces, 12, 27961, 10.1021/acsami.0c04939 Wang, 2019, Flexible and washable poly(ionic liquid) nanofibrous membrane with moisture proof pressure sensing for real-life wearable electronics, ACS Appl. Mater. Interfaces, 11, 27200, 10.1021/acsami.9b07786 Berger, 2017, Capacitive pressure sensing with suspended graphene-polymer heterostructure membranes, Nanoscale, 9, 17439, 10.1039/C7NR04621A Ma, 2017, Seriography-guided reduction of graphene oxide biopapers for wearable sensory electronics, Adv. Funct. Mater., 27, 10.1002/adfm.201604802