An ultrasensitive and stretchable strain sensor based on a microcrack structure for motion monitoring

Hao Sun; Xudong Fang; Ziyan Fang; Libo Zhao; Bian Tian; Prateek Verma; Ryutaro Maeda; Zhuangde Jiang

doi:10.1038/s41378-022-00419-6

An ultrasensitive and stretchable strain sensor based on a microcrack structure for motion monitoring

Microsyst Nanoeng. 2022 Sep 29:8:111. doi: 10.1038/s41378-022-00419-6. eCollection 2022.

Authors

Hao Sun^#^{1

2}, Xudong Fang^#^{1

2

3}, Ziyan Fang^{1

2}, Libo Zhao^{1

2

3}, Bian Tian^{1

2

3}, Prateek Verma⁴, Ryutaro Maeda^{1

2}, Zhuangde Jiang^{1

2}

Affiliations

¹ State Key Laboratory for Manufacturing Systems Engineering, International Joint Laboratory for Micro/Nano Manufacturing and Measurement Technologies, Collaborative Innovation Center of Suzhou Nano Science and Technology, Xi'an Jiaotong University, Xi'an, 710049 China.
² School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, 710049 China.
³ Overseas Expertise Introduction Center for Micro/Nano Manufacturing and Nano Measurement Technologies Discipline Innovation, and Xi'an Jiaotong University (Yantai) Research Institute for Intelligent Sensing Technology and System, Xi'an, China.
⁴ School of Chemical Engineering, University of Arkansas, Fayetteville, AR 72701 USA.

^# Contributed equally.

Abstract

Flexible strain sensors are promising candidates for intelligent wearable devices. Among previous studies, although crack-based sensors have attracted a lot of attention due to their ultrahigh sensitivity, large strain usually causes fractures in the conductive paths. Because of the unstable crack structure, the tradeoff between sensitivity and workable strain range is still a challenge. As carbon nanotubes (CNTs) and silver nanowires (AgNWs) can form a strong interface with the thermoplastic substrate and strengthen the conductive network by capillary force during water evaporation, CNTs and AgNWs were deposited on electrospun TPU fiber mats via vacuum-assisted filtration in this work. The prestretching treatment constructed a microcrack structure that endowed the sensor with the combined characteristics of a wide working range (0~171% strain), ultrahigh sensitivity (a gauge factor of 691 within 0~102% strain, ~2 × 10⁴ within 102~135% strain, and >11 × 10⁴ within 135~171% strain), a fast response time (~65 ms), small hysteresis, and superior durability (>2000 cycles). Subsequently, the sensing mechanism of the sensor was studied. Distributed microcrack propagation based on the "island-bridge" structure was explained in detail, and its influence on the strain-sensing behavior of the sensor was analyzed. Finally, the sensor was assembled to monitor various vibration signals and human motions, demonstrating its potential applications in the fields of electronic skin and human health monitoring.

Keywords: Nanowires; Sensors.