Highly anisotropic and flexible piezoceramic kirigami for preventing joint disorders

The prevention of work-related upper extremity musculoskeletal disorders (MSDs; e.g., neck pain and shoulder fatigue) requires frequent exercises of neck and shoulder that primarily rely on the assistance of joint motion monitoring devices. However, most available wearable healthcare sensors are rigid, bulky, and incapable of recognizing the full range of human motions. Here, we propose a kirigami-structured highly anisotropic piezoelectric network composite sensor that is able to monitor multiple information of joint motions, including bending direction, bending radius, and motion modes, and to distinguish them simultaneously within one sensor unit. On the basis of the modified template-assisted processing method, we design a functional piezoceramic kirigami with a honeycomb network structure that is stretchable (~100% strain), highly sensitive (15.4 mV kPa^-1), and highly anisotropic to bending directions (17.3 times from 90° to 0°). An integrated monitoring system is further established to alarm the prolonged sedentary behaviors, facilitating the prevention of upper extremity MSDs.