Effect of Interface Microstructures on the Performance of Droplet-Based Triboelectric Nanogenerator

Solid–liquid triboelectric nanogenerators (SL-TENGs) have attracted a lot of attention due to their high energy harvesting potential in special environments such as rainy conditions, marine settings, and biological systems. This study focuses on droplet-driven TENGs (D-TENGs) and optimizes their energy conversion efficiency through interface microstructure design. Using a photolithography-etching process, 4 types of polydimethylsiloxane (PDMS) microstructured surfaces (pyramidal, cylindrical, square pillar, and grating) were fabricated. By integrating multiphysics simulations and experimental analyses, the influence mechanisms of microstructure morphology on droplet dynamics and triboelectric output were systematically revealed. The results indicate that the cylindrical microstructure facilitates stable air cushion formation via axisymmetric flow constraints, significantly increasing the liquid–solid contact area and achieving an output voltage of 27.2 V, which is 3.49 times higher than that of a nonstructured surface. Further investigations demonstrate that microstructure feature size (optimal at 3 μm) and PDMS dielectric layer thickness (thinner layers enhance electric field intensity) are key parameters regulating output performance. Based on these findings, a self-powered sensing system was developed to simultaneously detect rainfall pH levels and suspended particulate matter concentrations. The output voltage exhibited a linear response (R² = 0.98) within the pH 3 to 7 range, and a synergistic attenuation effect was observed under extreme acidic conditions and high particulate concentrations. This study provides theoretical insights and technical pathways for applying D-TENGs in environmental monitoring and self-powered sensing.