Flexible unimodal strain sensors for human motion detection and differentiation

Multiple strain sensors are required to identify individual forces/stresses on human joints and recognize how they work together in order to determine the motion's direction and trajectory. However, current sensors cannot detect and differentiate the individual forces/stresses and their contributions to the motion from the sensors' electrical signals. To address this critical issue, we propose a concept of unimodal tension, bend, shear, and twist strain sensors with piezoelectric poly L-lactic acid films. We then construct an integrated unimodal sensor (i-US) using the unimodal sensors and prove that the i-US can detect and differentiate individual strain modes, such as tensioning, bending, shearing, and twisting in complex motion. To demonstrate the potential impact of unimodal sensors, we design a sleeve and a glove with the i-US that can capture wrist motions and finger movements. Therefore, we expect unimodal strain sensors to provide a turning point in developing motion recognition and control systems.

Lu Jin, Zhenhong Li, Zekun Liu, Bethany Richardson, Yan Zheng, Lulu Xu, Zhongda Chen, Heng Zhai, Hongdoo Kim, Qingwen Song, Pengfei Yue, Sheng Quan Xie, Kap Jin Kim, Yi Li