High-performance flexible and stretchable self-powered surface engineered PDMS-TiO2 nanocomposite based humidity sensors driven by triboelectric nanogenerator with full sensing range

Abstract

Harvesting electrical charge using triboelectrification provides a promising path to realizing uninterrupted self-powered sensors with application in wearable electronics and personal healthcare. This paper reports a high-performance flexible and stretchable self-powered humidity sensor based on triboelectric nanogenerators (TENG) that provides extreme responsivity, excellent repeatability with fast recovery time, and high selectivity. The device relies on a surface-engineered titanium oxide nanoparticle-silicone nanocomposite that generates triboelectric charge density strongly dependent on ambient humidity. The performance of the nanoengineered humidity sensor was systematically investigated at different humidity levels, which exhibits high responsivity (90% change for 75% RH change), a fast response time (1 s for 50% RH), a fast recovery time (3 s for 50% RH), and nearly full sensing range (0–99%). When activated by vertical contact separation at 2 Hz, the device generates a power density as high as 90 mW.m−2 and an open-circuit voltage of 50 V. An analytical model is derived to understand the underlying mechanism. The theoretical data explain the role of dielectric permittivity and surface area on the device operation, and the results are in good agreement with the experiments. The excellent combination of the properties suggests that these flexible TENGs can serve as reliable self-powered motion-driven humidity sensor.