Dog drooling a lot after playing outside - what to do?

Abstract

<h4>Hypothesis</h4>Droplet contact time on superhydrophobic surfaces is conventionally governed by the capillary-inertial timescale and remains nearly invariant for droplets of a given size. We hypothesize that manipulating the jet dynamics arising during droplet impact on superhydrophobic meshes can break this constraint, enabling reduced contact times without droplet fragmentation or mass loss.<h4>Experiments</h4>Droplet impact experiments were performed on superhydrophobic meshes (SHPoMs) with varied pore sizes and on hybrid configurations combining the mesh with an underlying superhydrophobic surface (SHPoS). High-speed imaging quantified the spreading, recoil, and jet evolution processes. A simple scaling model was developed to predict the influence of mesh geometry on droplet spreading and contact time.<h4>Findings</h4>Partial penetration of liquid through the mesh pores reduced the effective spreading diameter, achieving over 20% reduction in contact time, consistent with model predictions. Introducing an SHPoS beneath the mesh restricted jet elongation, inducing a pancake-bouncing mode that shortened contact time by more than 50% compared with conventional rebound. Optimal spacing of 200 μm between the SHPoM and SHPoS was identified for sustained pancake bouncing. A scaling model was developed to evaluate the sufficient condition for pancake bouncing. These findings reveal jet control as a powerful, fabrication-friendly strategy for tailoring droplet impact dynamics, offering practical benefits for self-cleaning, anti-icing, and thermal management applications.