Controlling shedding characteristics of condensate drops using electrowetting

TL;DR

This paper demonstrates how ac electrowetting with structured electrodes can effectively control condensate drop shedding, enhancing removal rates and pattern control on hydrophobic surfaces, with potential applications in heat transfer.

Contribution

It introduces a novel method using ac electrowetting with structured electrodes to manipulate condensate drop shedding and coalescence, optimizing removal efficiency.

Findings

Electrowetting reduces contact angle hysteresis, leading to smaller shedding radii.

Interdigitated electrodes with zigzag edges enhance coalescence and pattern control.

Intermittent voltage application further optimizes shedding characteristics.

Abstract

We show here that ac electrowetting (ac-EW) with structured electrodes can be used to control the gravity-driven shedding of drops condensing onto flat hydrophobic surfaces. Under ac-EW with straight interdigitated electrodes, the condensate drops shed with relatively smaller radii due to the ac-EW-induced reduction of contact angle hysteresis. The smaller shedding radius, coupled with the enhanced growth due to coalescence under EW, results in increased shedding rate. We also show that the condensate droplet pattern under EW can be controlled, and the coalescence can be further enhanced, using interdigitated electrodes with zigzag edges. Such enhanced coalescence in conjunction with the electrically-induced trapping effect due to the electrode geometry results in larger shedding radius, but lower shedding rate. However, the shedding characteristics can be further optimized by applying the electrical voltage intermittently. We finally provide an estimate of the condensate volume removed per unit time in order to highlight how it is enhanced using ac-EW-controlled dropwise condensation.