A Skin-Wearable Triboelectric Nanogenerator for Self-Powered Motion Monitoring and Energy Harvesting

Self-powered and wearable pressure sensors based on triboelectric nanogenerators (TENGs) have gained attention as promising candidates for tactile sensing and energy harvesting because of their design compatibility and ability to operate at low frequencies. While much research has focused on enhancing tribo-negative materials for flexible TENGs, the limited choices for tribo-positive materials have been a limiting factor. A crucial challenge in the development of wearable sensors is achieving biocompatibility without compromising broad-range sensitivity and energy-harvesting capabilities. Here we report a TENG based skin-wearable and self-powered pressure sensor by a simple fabrication using layer by layer deposition method. The flexible layered triboelectric nanogenerator (L-TENG) features a dielectric-to-dielectric configuration, with polytetrafluoroethylene (PTFE) and polymethyl methacrylate (PMMA) films serving as negative and positive triboelectric layers, respectively. These layers are sandwiched within a flexible and biocompatible polydimethylsiloxane (PDMS) matrix. A nanostructured PDMS surface obtained by oxygen plasma served as the structural backbone for the bottom indium tin oxide-copper electrode and overlying tribo-positive PMMA layer. The self-powered L-TENG sensor exhibited a broad range dual pressure sensitivity of 7.287 mV/Pa for low pressure and 0.663 mV/Pa for higher pressure ranges. Additionally, the L-TENG sensor adeptly detected physiological motions such as wrist extension and flexion, and finger bending angles while efficiently harvesting wasted energy from routine physical activities like walking and jogging. Notably, the maximum peak-to-peak voltages of 18.3 V and 57.4 V were measured during these motions. The L-TENG holds vast potential in wearable technology, spanning applications in healthcare, human-machine interfaces, and the powering of microelectronics from physical activities.<br/><br/>Keywords: skin-wearable, self-powered, wearable pressure sensing, triboelectric nanogenerator (TENG), energy harvesting, human motion monitoring