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Zhong F, Hu W, Zhu PN, Wang H, Ma C et al. Piezoresistive design for electronic skin: from fundamental to emerging applications. Opto-Electron Adv 5, 210029 (2022). doi: 10.29026/oea.2022.210029
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Review Open Access
Piezoresistive design for electronic skin: from fundamental to emerging applications
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Abstract
There is growing recognition that the developments in piezoresistive devices from personal healthcare to artificial intelligence, will emerge as de novo translational success in electronic skin. Here, we review the updates with regard to piezoresistive sensors including basic fundamentals, design and fabrication, and device performance. We also discuss the prosperous advances in piezoresistive sensor application, which offer perspectives for future electronic skin.-
Keywords:
- electronic skin /
- piezoresistive sensor /
- biocompatibility
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References
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Zhong F, Hu W, Zhu PN, Wang H, Ma C et al. Piezoresistive design for electronic skin: from fundamental to emerging applications. Opto-Electron Adv 5, 210029 (2022). doi: 10.29026/oea.2022.210029
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Figure 1.
Piezoresistive designs for engineering electronic skin. (a) Developmental history of flexible skin-like electronics (e.g. milestones in the shear force measurement, large-area manufacturing, spatial mapping, bioinspired manufacturing, interconnection between e-skin and live neurons, and self-healing capability)10-17 . (b) Scheme illustrating the design and applications of piezoresistive sensors.
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Figure 2.
Principles of piezoresistive effect. (a) Piezoresistance based on the geometric changes of metals and conducting polymers. i and ii represent the block and planar material geometries, respectively41,47. (b) Piezoresistance of semiconductor. Scheme illustrating the changes of charge carrier and energy band upon traction along the [111] direction in p–Si47. (c) Piezoresistance of composite materials based on the changes of conducting filler concentration and inter-filler distance48. (d) Structural piezoresistance based on the contact area and point changes of conducting architecture. Figure reproduced with permission from: (b) ref.47, Elsevier.
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Figure 3.
Development of piezoresistive sensors based on various materials. (a) Fabrication scheme and optical images of a hybrid metallic foam46. (b) Schematic illustrating the fabrication of CNTs/FKM nanocomposite50. FKM, fluoroelastomer; CNTs, carbon nanotubes; and TAIC, 1,3,5-triallyl-1,3,5-triazine-2,4,6 (1H,3H,5H)-trione. (c) Scheme illustrating the assembly of a MG/PU piezoresistive sensor51. MG, modified-graphite; PU, polyurethane; and PDMS, polydimethylsiloxane. (d) A flexible tactile sensor assembled from the 8x8 array of Si-strain gauges and the Si thin film transistors64. (e) Scheme illustrating the sandwich-structure of a PEDOT:PSS/Ag NW/PDMS component film74. PEDOT:PSS, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate); and Ag NWs: Ag nanowires. (f) mGN fillers form new conducting paths under pressure80. mGN, magnetic reduced graphene oxide@nickel nanowire. Figure reproduced with permission from: (a) ref.46, (f) ref.80, American Chemical Society; (c) ref.51, under a Creative Commons Attribution 4.0 International License; (d) ref.64, AIP Publishing.
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Figure 4.
Piezoresistive design and manufacture with singular structure. (a) Piezoresistance of an artificial structured sensor based on contact area changes91. ITO, indium tin oxide; PET, polyethylene terephthalate; SWCNTs, single-walled carbon nanotube; PDMS, polydimethylsiloxane. (b) Scheme illustrating the lotus-leaf-inspired piezoresistive design and assembly98. (c) Scheme illustrating the rose-petal-inspired piezoresistive design and assembly99 and the shark-skin-inspired piezoresistive design and assembly101. (d) Scheme illustrating the spider-leg-joint-inspired piezoresistive design with plenty of cracks102. Figure reproduced with permission from: (a) ref.91, (d) ref.102, Elsevier; (c) ref.101, Elsevier and ref.99, Royal Society of Chemistry.
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Figure 5.
Sensitivities of different microstructure sensors. ITO, indium tin oxide; MWNT, multiwalled carbon nanotubes; and PDMS, polydimethylsiloxane. Figure reproduced with permission from ref.94, under a Creative Commons Attribution 4.0 International License.
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Figure 6.
Piezoresistive design and manufacture with hierarchical structure. (a) Multiple dome structures as piezoresistance sensing layer86. (b) Multiple structure comprising of dense protuberances and porous structure as piezoresistance sensing layer106. HPM, hybrid porous microstructure; and CNT, carbon nanotubes. (c) Piezoresistive sensitivities based on the sensing layers comprising of rough-to-rough, rough-to-flat and flat-to-rough surfaces107. Figure reproduced with permission from: (a) ref.86, (b) ref.106, (c) ref.107, American Chemical Society.
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Figure 7.
Design and manufacture of fibre piezoresistive sensor. (a) Schematic of a rGO-Ag NW@cotton fibre, through immersion of cotton fibres in a reductive solution containing GO and AgNW112. GO, graphene oxide; rGO, reduced GO; and AgNW, Ag nanowires. (b) Scheme of an electrospun fibre piezoresistive sensor and its sensing mechanisms during pressure and blending110. KL, kraft lignin. (c) Scheme of a wet-spinning single-fibre piezoresistive sensor122. Figure reproduced with permission from: (a) ref.110, (b) ref.112, Elsevier; (c) ref.122, American Chemical Society.
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Figure 8.
Piezoresistive design and manufacture with spongy structure. (a) Freeze drying for the fabrication of piezoresistive sponge68. (b) Directional freeze drying of the fabrication of piezoresistive wave-shaped sensing layers127. CNC, cellulose nanocrystals. (c) Dip coating of as-fabricated sponge with conducting materials130. PU, polyurethane; and MWCNT, multiwalled carbon nanotubes. (d) Sacrificial template for the fabrication of piezoresistive sponge131. (e) Sponge-based hierarchical structure (e.g. cracks) for piezoresistive sensor134. Figure reproduced with permission from: (a) ref.68, (d) ref.131, (e) ref.134, American Chemical Society; (b) ref.127, (c) ref.130, Royal Society of Chemistry.
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Figure 9.
Additive manufacturing for piezoresistive sensor. (a) Drop-on-demand material jetting for the facial fabrication of piezoresistive structures143. MCF, milled carbon fibers; and SR, silicone rubber. (b) 3D printing of human-skin-inspired texture as piezoresistive sensing layers144. CNT, carbon nanotube. (c) Application of a 3D printed piezoresistive sensor for robotic fingertips to sense force145. (d) 3D printing of conducting composite for piezoresistive sensor148. SIS, polystyrene–polyisoprene–polystyrene. (e, f) 3D printing of different structure parameters (e.g. diameter, interaxial angle, and interlayer space) for piezoresistive sensor149. GF, gauge factor. Figure reproduced with permission from: (a) ref.143, (e, f) ref.149, Elsevier; (c) ref.145, American Chemical Society; (d) ref.148, Royal Society of Chemistry.
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Figure 10.
Piezoresistive sensor for health monitoring. (a) Detection of physical activities by piezoresistive sensor, including the swallowing (A and B: the pharyngeal and esophageal phase, respectively) and the posture of human back152. (b) Detection of physiological activities (e.g. wrist and jugular venous pulse) at high sensitivities153. (c) Detection of myocardic activities (e.g. heartbeats at breathing and not breathing) by a piezoresistive sensor154. (d) Identification of different mechanical stimuli, including pressure, shear and torsion force132. Figure reproduced with permission from: (a) ref.152, (d) ref.132, Elsevier; (b) ref.153, (c) ref.154, American Chemical Society.
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Figure 11.
Piezoresistive sensor for intelligent healthcare. (a) Piezoresistance for visiual, alarm, wireless and implanted applications35. (b) Triode-mimicking pressure sensor for intelligent shoe pad159. (c) Scheme illustrating a monitoring system developed based on the intelligent shoe pad in (b)159. (d) Continuous and multiple signals from the integrated gait monitoring system in (c)159. Figure reproduced with permission from: (a) ref.35; (b–d) ref.159, American Chemical Society.
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Figure 12.
Piezoresistive sensor for intelligent speech recognition. (a) Piezoresistive detection of sound (e.g. word recognition, volume detection, and voice recognition)68. (b) Response of a MXene-based piezoresistive sensor to the audio outputs at different volumes162. (c) Anti-interference voice recognition by a skin-attachable piezoresistive sensor165. Figure reproduced with permission from: (a) ref.68, (b) ref.162, (c) ref.165, American Chemical Society.
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Figure 13.
Piezoresistive sensor for prosthetics and robots. (a) Manipulating the robot arm by a piezoresistive sensor for music playing169. (b) Large-area force distribution detected by fibre piezoresistive sensor array171. (c) Piezoresistive sensor for the real-time monitoring of robot−tissue collision/interaction in surgical robots173. (d) Development of an artificial afferent nerve based on multiple piezoresistive sensors175. Figure reproduced with permission from: (a) ref.169, (b) ref.171, (c) ref.173, American Chemical Society.
