Design principle of ridge-textured superhydrophobic surfaces for inducing pancake bouncing

Abstract

Reducing contact time of droplets impacting on solid surfaces plays an important role in various applications such as anti-icing and energy harvesting. Pancake bouncing on superhydrophobic surfaces decorated with arrays of pillars or ridges can remarkably reduce the contact time. However, the trigger of pancake bouncing is rigorous, and precise controls of impact conditions and surface structures are the significant precondition for utilizing pancake bouncing. Here, we numerically investigate the dynamic process of droplets impacting on ridge-textured superhydrophobic surfaces, and theoretically establish the design principle for inducing pancake bouncing. Compared with conventional bouncing on flat superhydrophobic surfaces, the contact time of pancake bouncing on ridge-textured superhydrophobic surfaces is effectively reduced by 60–70%. The transition of bouncing depends on the time for the penetrated liquid to drain out from surface structures and the energy of droplets when drainage finishes. Correspondingly, time and energy demands are needed to be satisfied to induce pancake bouncing, and the two demands compose the design principle. Initial parameters are integrated into two parameters only related to droplets and surfaces, respectively. The design principle accurately determines the proper structure parameters for pancake bouncing under different impact conditions, which provides useful guidance for the design of superhydrophobic surfaces