Breath figures under electrowetting: electrically controlled evolution of drop condensation patterns

TL;DR

This paper demonstrates how electrowetting with structured electrodes can control drop condensation patterns, leading to improved heat transfer by altering droplet distribution, coalescence, and shedding behavior.

Contribution

It introduces a method to electrically manipulate condensation patterns and droplet dynamics on hydrophobic surfaces using structured electrodes and applied voltage.

Findings

Electrowetting aligns drops and enhances coalescence.

Drop size distribution shows self-similar evolution under EW.

Electrowetting reduces surface coverage and promotes earlier drop shedding.

Abstract

We show that electrowetting (EW) with structured electrodes significantly modifies the distribution of drops condensing onto flat hydrophobic surfaces by aligning the drops and by enhancing coalescence. Numerical calculations demonstrate that drop alignment and coalescence are governed by the drop size-dependent electrostatic energy landscape that is imposed by the electrode pattern and the applied voltage. Such EW-controlled migration and coalescence of condensate drops significantly alter the statistical characteristics of the ensemble of droplets. The evolution of the drop size distribution displays self-similar characteristics that significantly deviate from classical breath figures on homogeneous surfaces once the electrically-induced coalescence cascades set in beyond a certain critical drop size. The resulting reduced surface coverage, coupled with earlier drop shedding under EW, enhances the net heat transfer.