Droplet impact dynamics on an elastic circular membrane for energy harvesting

While droplet impacts on rigid substrates have been widely studied, their interaction with elastic circular membranes remains less understood. In this study, we investigate the dynamic response of circular elastic membranes to droplet impact, focusing on the interplay between droplet spreading and membrane deformation. High-speed imaging shows that both the droplet spreading radius and membrane displacement are strongly influenced by impact velocity, membrane thickness, diameter, and elasticity. The membrane's oscillations deviate from simple harmonic motion and are governed by the coupled effects of the membrane's natural frequency and the droplet's intrinsic oscillation frequency. To interpret these dynamics, we develop a fluid–structure interaction model that predicts deformation amplitude and vibration characteristics in good agreement with experiments. Based on this understanding, we propose a hybrid energy harvester integrating triboelectric and piezoelectric elements on the membrane. Our results indicate that droplet spreading enhances triboelectric output, while membrane oscillation drives piezoelectric generation. This study provides new insights into droplet–membrane dynamics and offers design guidelines for soft-membrane-based energy harvesting from ambient raindrop impacts.