Breaking the capillary limit: jet-controlled ultrafast droplet rebound on superhydrophobic meshes

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.

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.

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.