Study of the enhanced electricity output of a sliding droplet-based triboelectric nanogenerator for droplet sensor design

Triboelectric nanogenerators are establishing themselves as promising candidates for realizing high-efficient energy harvesting from largely available droplets. However, the conventional droplet-based liquid-solid triboelectric nanogenerator (DLS-TENG) has energy conversion efficiency of only ~ 2 × 10−5%. Here, an optimized structure of DLS-TENG with an additional top electrode is proposed aiming to increase the energy conversion from mechanical energy of sliding droplets into electricity. A peak short circuit current output is obtained up to 0.48 μA, which represents an increase of about 1000 times comparing to the same device working in single-electrode mode. The relationship between the time-domain current waveform and the movement of the droplet is analyzed in details using the equivalent circuit model to study the unique features of the electricity output from sliding motion. Critical parameters, including the dripping frequency, droplet releasing height and the liquid property, are discussed to reveal the dominant factor to maximize the triboelectric output from droplet sliding. Demonstrations of applications in droplet detecting with high accuracy and microfluidic sensor offer new significant insights into the design of triboelectric microfluidic and droplet sensors.