High‐Efficiency Reclamation of Oscillating Energy During Multiple Droplets Impact on Bionic Lotus Surface

Abstract Droplet bouncing on special wettability surface is common and important in daily life and engineering applications (anti‐icing and drag reduction, etc.). However, there are few studies on the multiple droplets impact and there is a lack of systematic research on the interaction of oscillation and bounce. Here, the impact and oscillation of multiple droplets on the porous superhydrophobic bionic lotus surface are studied by a high‐speed camera system. On the bionic lotus surface (Surf‐1), an impacting droplet can merge another larger sessile droplet and bounce off. Comparing with single droplet impact, it is suggested that multiple droplets impact make more efficient use of the air cushion on the micrometer‐nanometer‐scale binary structure (MNBS) and show the self‐cleaning performance of Surf‐1 better. Moreover, with the theory for damped harmonic oscillators, it is found that Surf‐1 can prolong the oscillation of droplets (last >250 ms) and slow down the attenuation of energy. The energy can be efficiently recycled to the bounce by shortening the droplet impact interval (ti). The fundamental understanding of multiple droplets impact and the reclamation of oscillating energy are beneficial for scientific design of new surface and engineering applications.