Flexible Piezoelectric Devices and Their Wearable Applications

doi:10.15541/jim20220549

Abstract

Abstract:

Wearable instruments are functional devices that can be worn on human body, sensing, transmitting and processing body or environmental information in real time, and show broad application prospects in medical health, especially artificial intelligence, sports and entertainment. With the development of wearable instruments, various flexible sensors have emerged. Flexible mechanical sensors based on piezoelectric effect have attracted much attention because of their advantages of wide sensing frequency, fast response, good linearity, and self-power supply. However, traditional piezoelectric materials are mostly brittle ceramics and crystalline materials, which limit their application in flexible devices. With the deepening of research, more and more flexible piezoelectric materials and piezoelectric composites continue to emerge, injecting new development vitality into flexible wearable mechanical devices. This article mainly summarizes the cutting-edge progress of flexible wearable piezoelectric devices, including piezoelectric principle, preparation and performance improvement methods of flexible piezoelectric materials. In addition, the main application directions of flexible wearable piezoelectric devices, including medical health and human-computer interaction, as well as the challenges and opportunities encountered, are summarized.

Key words: mechanical sensor, wearable device, piezoelectric effect, preparation method, flexibility

CLC Number:

TB381

MAO Aiqin, LU Wenyu, JIA Yanggang, WANG Ranran, SUN Jing. Flexible Piezoelectric Devices and Their Wearable Applications[J]. Journal of Inorganic Materials, 2023, 38(7): 717-730.

Figures/Tables 7

Fig. 1 Materials and their preparation and application for flexible piezoelectric devices

Fig. 2 Fundamental principles of piezoelectric effect[1-2,10,13⇓-15] (a) Schematic diagram of piezoelectric effect[1]; (b) Structure and piezoelectric effect of BTO[2]; (c) Structure and piezoelectric effect of ZnO[10]; (d) Structure and piezoelectric effect of monolayer MoS2[13]; (e) Different crystalline phase structures of PVDF[14]; (f) Structure and piezoelectric effect of chitin[15]

Fig. 3 Preparation methods and surface modification[57⇓⇓⇓⇓-62] (a) Schematic diagram of electrospinning[57]; (b) Electrospun PVDF fibers with different morphologies[58]; (c) Schematic diagram of the preparation of thin films by LB method[59]; (d) PDA-coated BTO[60]; (e) Ag-decorated BTO[61]; (f) Carbon-coated BTO[62]

Fig. 4 Chemical doping and structural improvement[84-85,87 -88] (a) Tb-doped ZnO[84]; (b) Output of modified ZnO with different concentrations[84]; (c) Effect of doping with different halogen elements on ZnO[85]; (d) Effect of doping with different halogen elements on the piezoelectric output of ZnO[85]; (e) Schematic diagram of the GAMF device[87]; (f) Piezoelectric active layers with different structures[88] (1 kgf=9.8 N)

Fig. 5 Physiological monitoring applications of flexible wearable devices[45,89] (a) Principle of blood pressure monitoring with dual-sensor[89]; (b) Principle of blood pressure monitoring with single-sensor[89]; (c) Schematic diagram of interlocking ZnO NRs[45]; (d) Interlocking ZnO structure for monitoring breathing, heartbeat and leg muscle movement[45]

Fig. 6 Flexible wearable devices for wound healing and implantable applications[90⇓⇓-93] (a) PVDF device for promoting wound healing[90]; (b) PVDF device with composite electrodes for wound healing and nerve cell restored[91]; (c) Ultraflexible piezoelectric energy harvesting and sensing integrated devices[92]; (d) Schematic diagram of implantable ultrasonic piezoelectric device[93]; (e) Analgesic effects of wireless ultrasound-driven implantable devices

Fig. 7 Flexible wearable devices for human-computer interaction[94⇓⇓-97] (a) Intelligent piezoelectric tactile sensor[94]; (b) Visualized force glove and its structure[95]; (c) Wireless controlled manipulator[96]; (d) Gesture recognition glove[97]

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