An ultra-flexible temperature-insensitive strain sensor

Abstract

Wearable flexible strain sensors that can sense human motion are expected to be applied in healthcare and metaverse applications. Examples of such sensors are resistive strain sensors, which are characterized by high gauge factors and simple device structures and can be fabricated using solution processes. The performance of resistive strain sensors is affected by changes in the resistance due to temperature. To improve temperature performance, researchers have studied strain sensors with a temperature coefficient of resistance (TCR) close to zero. However, solution-processed near-zero-TCR strain sensors with excellent flexibility have not yet been developed. In this study, using a sensor material consisting of a conductive polymer and Ag nanoparticles, a near-zero-TCR strain sensor is developed with a minimum bending radius of 0.14 mm at a total device thickness of 14 μm. The sensor material exhibits lower sensitivity to temperature and higher sensitivity to strain, with a TCR of 0.11% K⁻¹ and gauge factor of 64 at a strain of 6.1%. Furthermore, it is sufficiently durable to operate even after 1000 cycles at a strain of 3.6%. When the device is attached to the inside of an arm and the arm is bent deeply in a temperature-changing environment, it operates without failure and senses arm bending without being affected by the environmental or body temperature.