Dual nano/micro tip-array based liquid-solid interface for ultrahigh sensitive triboelectric pressure sensors

Specific liquid-solid contact electrification demonstrates a unique and promising generation of pressure sensors. However, improving sensitivity at the liquid-solid interface remains a substantial challenge. In this work, we present a ferrofluid-based triboelectric pressure sensor (FTPS) based on a strain-concentrated dual tip-array design between the liquid and solid phases. A silicone rubber film with a conical micro/nanostructure array and a ferrofluid with incisive spike microstructures tuned by a solid baseplate are employed as triboelectric pairs. The array-shaped microstructures of the solid- and liquid-sensing layers exhibit an opposing arrangement, manifesting a dual tip-array structure. The strain concentration effect arises from the coupling of high hydrophobicity caused by solid tip microstructures and high sharpness of liquid tip microstructures. In a load-bearing structure, there is a significant increase in strain when a sudden change in shape occurs. The sensitivity of the FTPS is positively correlated with the vertical deformation at the interface per unit pressure. Thus, an unprecedentedly high sensitivity of 38.84 kPa- 1 and an inconceivably low detection limit of 0.76 Pa are attained. Finally, wind speed and direction detection with high sensitivity and stability based on the FTPS is demonstrated, indicating extensive practical applications for environmental monitoring and meteorological forecasting.