Flexible and Highly Sensitive Strain Sensors Fabricated by Pencil Drawn for Wearable Monitor

• Published in: Advanced functional materials Vol. 25; no. 16; pp. 2395 - 2401
• Main Authors: Liao, Xinqin, Liao, Qingliang, Yan, Xiaoqin, Liang, Qijie, Si, Haonan, Li, Minghua, Wu, Hualin, Cao, Shiyao, Zhang, Yue
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 22.04.2015
• Subjects: Devices; Electric potential; flexible electronics; microcontact sensing; Monitoring; Pencils; Printing; printing technique; Sensors; Strain; strain sensors; Wearable; wearable monitor
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201500094

Functional electrical devices have promising potentials in structural health monitoring system, human‐friendly wearable interactive system, smart robotics, and even future multifunctional intelligent room. Here, a low‐cost fabrication strategy to efficiently construct highly sensitive graphite‐based strain sensors by pencil‐trace drawn on flexible printing papers is reported. The strain sensors can be operated at only two batteries voltage of 3 V, and can be applied to variously monitoring microstructural changes and human motions with fast response/relaxation times of 110 ms, a high gauge factor (GF) of 536.6, and high stability >10 000 bending–unbending cycles. Through investigation of service behaviors of the sensors, it is found that the microcracks occur on the surface of the pencil‐trace and have a major influence on the functions of the strain sensors. These performances of the strain sensor attain and even surpass the properties of recent strain sensing devices with subtle design of materials and device architectures. The pen‐on‐paper (PoP) approach may further develop portable, environmentally friendly, and economical lab‐on‐paper applications and offer a valuable method to fabricate other multifunctional devices. Easy‐to‐fabricate, cost‐effective, soft, lightweight, versatile sensors revolutionize the sensing technology and can be applied in personal electronic devices, artificial intelligence systems, and structural health monitoring. The pen‐on‐paper approach endows the pencil trace based on a printing paper with strain‐sensing capability for monitoring the rapid microstrain structural variation, book folding, and human motion. The sensors are low carbon footprint, disposable, and green products.