Achieving ultrasensitivity and high breathability in biodegradable piezoresistive electronic skins

Nonbiodegradable components, such as synthetic polymers, have been widely used in the fabrication of flexible piezoresistive sensors and electronic skins (e-skins), resulting in the generation of electronic waste (e-waste) and toxic by-products. To overcome this issue, a wide range of biodegradable natural biopolymers and synthetic polymers have been employed. However, most of the current biodegradable e-skins demonstrate limitations such as low sensitivity, poor electrical conductivity, limited breathability, and low stability. To address these limitations, this study proposes a highly breathable and ultrasensitive piezoresistive e-skin based on the oxidized single-walled carbon nanotube (Ox-SWCNT)/silver nanowire (AgNW)-coated leaf skeletons. The developed disposable piezoresistive e-skin exhibits a remarkable performance including high sensitivity (19.75 ± 1.5 kPa−1, <3 kPa), sensing range of ≤42 kPa, ultralow limit of detection (∼0.27 Pa), linearity for low- and high-pressure regimes, high flexibility, high stability (3000 cycles), low weight, ultrahigh breathability, and biodegradability. In addition, the developed leaf-based e-skin demonstrates outstanding sensing performance in human-motion monitoring by detecting various motions such as subtle and vigorous flexions, airflow, and vocal-cord vibrations. The proposed piezoresistive e-skin is a promising platform for the development of various low-cost, biocompatible, fully biodegradable, and point-of-care (POC) e-skins for a wide range of subtle and vigorous pressure-monitoring applications including human–machine interfaces (HMIs), robotics, prosthesis, and flexible electronics.