Multilayered MoS2 Sphere-Based Triboelectric-Flexoelectric Nanogenerators as Self-Powered Mechanical Sensors for Human Motion Detection

High-performance, wearable, and self-powered mechanical sensors for human health monitoring, motion detection systems, and human-machine interfaces are attracting attention owing to the increased interest in green energy. Piezoelectric and triboelectric effects are being exploited to develop various types of self-powered mechanical sensors; however, unresolved issues such as complicated processes and limitations in material selection and practical applications remain. A type of effective self-powered mechanical sensor based on the hybrid triboelectric-flexoelectric effect of multilayered MoS2 hollow spheres is reported herein. This triboelectric-flexoelectric mechanical sensor (TFMS) exhibits superior sensing characteristics, including wide-range pressure detection and superior stability, owing to the remarkable hybrid triboelectric-flexoelectric effect of optimized MoS2 hollow spheres under stress. In addition, the operating mechanism of the fabricated TFMS is discussed based on the size and number of the multilayered MoS2 spheres using finite element method (FEM) simulations of the effective stress under pressure changes. Furthermore, the effective operation of the sensor in detecting various human physiological motions from the wrist pulse to walking/ running is demonstrated. These results are expected to promote the development of advanced mechanical sensors for applications such as next and human-machine interfaces.