Novel Linear, Piezoresistive, Auxetic Sensors Coated by AAA Battery Active Carbons with Supreme Sensitivity for Human Body Movement Detection

Herein, a novel strategy for creating low-cost, sustainable, piezoresistive auxetic sensors using the active carbon in consumed AAA batteries, promoting a circular economy, is presented. An auxetic structure with a fixed Poisson's ratio during the strain is designed for sensing. The sensor substrate is silicone RTV2, and the sensing element is the active carbon in AAA batteries chopped to microscale particles using an ultrasonic wave. The sensor mold is designed using Solidworks software and produced using a computer numerical control device and EdgeCam2014 software. The coating process is performed by spraying the prepared particles on the molded auxetic structure and putting the coated auxetic structure under ultraviolet ray to prepare the final sensor. Sensitivity tests are performed, and the results show that the proposed sensor has a better sensitivity of about 1000% and 410% than the previous mixed and layered composite auxetic counterparts. The proposed sensor has linear sensitivity during the strain (estimated with a line with a slope of 0.64) while previous ones have a nonlinear performance (estimated at least with two lines). The sustainable sensor is implemented to detect the movements of the human body, including the movements of the wrist, finger, elbow, and forearm.

Automated summary

This study presents a novel strategy to create low-cost and sustainable piezoresistive auxetic sensors using active carbon from consumed AAA batteries, contributing to a circular economy. The sensors are made with an auxetic structure that has a fixed Poisson's ratio during strain and utilizes silicone RTV2 as a substrate and microscale active carbon particles as the sensing element. The sensors achieve a sensitivity improvement of approximately 1000% and 410% compared to previous mixed and layered composite auxetic counterparts. The linear sensitivity of the proposed sensors during strain, estimated with a slope of 0.64, distinguishes them from previous sensors with nonlinear performances. These sustainable sensors are successfully implemented in detecting various human body movements, such as those in the wrist, finger, elbow, and forearm.