Critical contact angle of a bouncing droplet

Bouncing droplets on solid surfaces is of great significance in diversified applications such as anti-icing and self-cleaning. It is important to establish a unified model to predict whether an impacting droplet can rebound from a surface or not. This work focuses on the rebound dynamic of a droplet impacting a hydrophobic surface via theoretical methods. Based on energy conservation, a new theoretical model to predict the rebound behavior of an impacting droplet is established. For an ideal surface, the contact angle hysteresis Delta theta can be ignored and the rebound condition is theta >= theta (c,i), where theta is the equilibrium contact angle and theta (c,i) is the critical rebounding contact angle (CRCA) of an ideal surface. For a real surface, Delta theta is considered and the rebound condition is theta (r) >= theta (c,r), where theta (r) is the receding contact angle and theta (c,r) is CRCA of a real surface. Especially, when Delta theta is not large enough, the rebound condition for a real surface can be expressed as theta (r) >= theta (c,i). This work is the first to establish the theoretical model considering both the energy dissipation throughout the impact process and the contact angle hysteresis, which shows a higher consistency with the previous works.

Automated summary

The establishment of a unified model for predicting the rebound behavior of droplets on solid surfaces is of great significance. This study investigates the rebound dynamics of droplets impacting hydrophobic surfaces using theoretical methods. A new theoretical model based on energy conservation is proposed to predict the rebound behavior of droplets. The results show that the theoretical model considering both energy dissipation throughout the impact process and contact angle hysteresis is more consistent with previous studies.