Regulation of droplet nucleation and sweeping on wedge-shaped superhydrophobic surfaces

The droplet nucleation and sweeping dynamics critically govern the condensation and self-cleaning functionality of superhydrophobic surfaces, yet their synergistic regulation remains underexplored. Four wedge-shaped micropillar architectures (5/10 μm heights) were investigated via combined condensation experiments and multiphase flow simulations. Geometric asymmetry-induced capillary force gradients were found to simultaneously enhance nucleation density and sweeping efficiency. The 10 μm flower-like surface achieved 26.67 × 108 droplets/m2 nucleation density (592% higher than conventional surfaces) with 563% faster nucleation, while enabling removal of 24 droplets per sweeping event and a 378.8% increase in frequency, resolving the historical nucleation-sweeping trade-off. Mechanistically, increased pillar height enhances nucleation by extending three-phase contact lines and reducing critical film rupture thickness, while intensified capillary gradients during coalescence drive nonlinear sweeping improvements via amplified energy conversion. Simulations confirm superior post-coalescence X-direction velocity (0.0317 m/s) and angular velocity (300.22 rad/s) on optimized surfaces, directly linking performance to capillary gradients. Design strategies for engineering superhydrophobic surfaces that synergistically integrate high-flux condensation and ultrafast self-cleaning are established in this work.