Suppressing the Leidenfrost effect by air discharge assisted electrowetting-on-dielectrics

Abstract

The Leidenfrost effect for a droplet on an over-heated substrate always results in a superhydrophobic state, significantly hindering the water evaporation for heat dissipation. Here, we demonstrate a strategy of air discharge assisted electrowetting-on-dielectrics (ADA-EWOD), overcoming this challenge. This strategy increases the solid surface free energy by generating air discharge near the three-phase contact line of the droplet and combines it with the electromechanical force to decrease the contact angle, which makes ADA-EWOD have stronger wetting capabilities than traditional electrically control methods that only rely on electromechanical force. The water contact angle on an over-heated surface (above 350 °C) is decreased from nearly 180° down to less than 10°. This superhydrophilicity at high temperature reduces the droplet lifetime by at least 10 times, well inhabiting the Leidenfrost effect. Furthermore, we use ADA-EWOD in droplet evaporation for heat dissipation, where a heated silicon wafer at 600 °C is cooled down to less than 200 °C within 20 s. We believe that the present work provides a perspective on suppressing the Leidenfrost effect, which may have important potential applications in the field of heat dissipation.