Bouncing–pinning criterion for a drop impacting on a superhydrophobic surface

Abstract

Drop impact on non-wetting surfaces has garnered significant interest due to its potential applications in water repellency, drag reduction, self-cleaning, and anti-icing. However, there are instances where a droplet fails to rebound from a superhydrophobic surface. It has been reported that the combined effect of gravito-capillary length and visco-capillary length determines the pinning–bouncing criteria. While the fluid properties, such as viscosity and weight, are often considered primary factors influencing droplet rebound, this study highlights the crucial role of surface characteristics, particularly the contact angle hysteresis, in determining post-impact behavior. We propose a modified criterion that predicts droplet bouncing and pinning on superhydrophobic surfaces by integrating both fluid properties and the contact angle hysteresis of the surface. The findings emphasize the importance of surface morphology in droplet dynamics, providing a more comprehensive understanding of droplet behavior on non-wetting surfaces.