Progress of biomass materials in triboelectric flexible sensors

Biomass friction electric flexible sensors are flexible sensors based on easily degradable and biocompatible biomass materials, consisting of positive and negative friction layers, and do not require external power supply, which are convenient, flexible, sensitive, renewable, etc., and have been comprehensively developed in the fields of human body movement monitoring, e-skinning and soft robotics. This paper firstly introduces the classification of self-powered flexible sensors based on different power supply principles, including piezoelectric self-powered flexible sensors, thermoelectric self-powered flexible sensors, friction electric self-powered flexible sensors and photoelectric self-powered flexible sensors, with a focus on the friction electric type. A further overview is given on the study of various types of biomass materials in friction electric flexible sensors, including cellulose, chitosan, lignin, sodium alginate and collagen fibres. Then the structure types of friction electric flexible sensors, such as hydrogel type, aerogel type, and film type, are discussed. Finally, the material selection, design types, additional properties and application prospects of biomass friction electric flexible sensors are prospected.