Stretchable and calibratable graphene sensors for accurate strain measurement

Abstract

Stretchable nanomaterial-based strain sensors are essential to soft electronics and robotics and wearable devices. A sensitivity graph for those reported highly stretchable sensors is often divided into a few nearly linear zones resulting in several gauge factors, which poses a challenge for calibration. We herein report that (i) a gauge factor does not have to be one constant number because calibration merely relies on the relationship between the input and the output data and (ii) calibration accuracy relates to linear regression analysis between testing data and a fitted graph, i.e. calibration accuracy corresponding to coefficient of determination (R²). It is the first time that a stretchable strain sensor is reported as a gauge, where the resolution is an essential element of a gauge. A stretchable elastomer/graphene strain sensor developed in this study is calibrated as a proper gauge to provide strain readings with high resolution up to 0.089% and accuracy of over 99.7%, where resolution refers to the minimum dimension of accurate measurement. The idea of calibration in this study could advance many published wearable sensors to gauges. Sensing parameters are also provided with practical meanings for calibration.