Fig. 1. The concept, structure and mechanism of the lip-language decoding system supported by triboelectric sensors.

a Schematic illustration of the lip-language decoding system and its components, including triboelectric sensors, signal processing and deep learning classifiers. b Structure scheme for the flexible triboelectric sensor. c Schematic diagram of four stages of charge transfer in one mouth open-close cycle. The mouth-opening process pushes the sensor, and the mouth-closing process releases the sensor, resulting in the flow of current in opposite directions.