Bioinspired Self-Powered Piezoresistive Sensors for Simultaneous Monitoring of Human Health and Outdoor UV Light Intensity

• Published in: ACS applied materials & interfaces Vol. 14; no. 4; pp. 5101 - 5111
• Main Authors: Yu, Zhichao, Xu, Jianhui, Gong, Hexiang, Li, Yuxuan, Li, Ling, Wei, Qiaohua, Tang, Dianping
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 02.02.2022
• Subjects: Biological and Medical Applications of Materials and Interfaces; Cotton Fiber; Electric Conductivity; Gossypium - chemistry; Graphite - chemistry; Humans; Monitoring, Physiologic - instrumentation; Monitoring, Physiologic - methods; Movement; Nanotubes - chemistry; Nanowires - chemistry; Pulse; Respiratory Rate - physiology; Speech - physiology; Ultraviolet Rays; Wearable Electronic Devices; Zinc Oxide - chemistry; cotton fiber; ZnO nanoarrays; wearable sensors; UV photodetector; motion monitoring
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.1c23604

The exact fabrication of precise three-dimensional structures for piezoresistive sensors necessitates superior manufacturing methods or tooling, which are accompanied by time-consuming processes and the potential for environmental harm. Herein, we demonstrated a method for in situ synthesis of zinc oxide nanorod (ZnO NR) arrays on graphene-treated cotton and paper substrates and constructed highly sensitive, flexible, wearable, and chemically stable strain sensors. Based on the structure of pine trees and needles in nature, the hybrid sensing layer consisted of graphene-attached cotton or paper fibers and ZnO NRs, and the results showed a high sensitivity of 0.389, 0.095, and 0.029 kPa–1 and an ultra-wide linear range of 0–100 kPa of this sensor under optimal conditions. Our study found that water absorption and swelling of graphene fibers and the associated reduction of pore size and growth of zinc oxide were detrimental to pressure sensor performance. A random line model was developed to examine the effects of different hydrothermal times on sensor performance. Meanwhile, pulse detection, respiration detection, speech recognition, and motion detection, including finger movements, walking, and throat movements, were used to show their practical application in human health activity monitoring. In addition, monolithically grown ZnO NRs on graphene cotton sheets had been integrated into a flexible sensing platform for outdoor UV photo-indication, which is, to our knowledge, the first successful case of an integrated UV photo-detector and motion sensor. Due to its excellent strain detection and UV detection abilities, these strategies are a step forward in developing wearable sensors that are cost-controllable and high-performance.