Regulating droplet impact on a solid hydrophobic surface through alternating current electrowetting-on-dielectric

Abstract

The phenomenon of droplet impact is commonly found in industrial and agricultural processes. The basic characteristics and theories of a droplet impacting solid walls have been extensively studied, but the regulation of the droplet impact phenomenon has not been adequately examined. This study investigates the regulation of droplet impact on a hydrophobic surface based on alternating current electrowetting-on-dielectric (AC EWOD). When a water droplet impacts a virgin Teflon surface at 1.06 m/s, the phenomenon of partial rebound occurs. When an AC voltage is applied to an electrode pair underneath the Teflon layer, the droplet is stabilized on the hydrophobic surface after impact. To investigate the mechanism of influence of the AC signal on the regulation of droplet impact, the variation in the spread diameter and height of the droplet were characterized at different frequencies and amplitudes of the AC signal. An oscillation in the diameter of the droplet was observed in the retraction stage with the application of AC EWOD, which was the dominant effect in neutralizing the retraction kinetic energy and yielded the rebound inhibition effect. A transition diagram between partial droplet rebound and rebound inhibition was plotted in terms of voltage, frequency, and the Weber number, and theoretical analysis was carried out to determine the retraction kinetic energy dissipated by the viscous force when the AC EWOD signal was applied.

Controlling droplet splashing and bouncing by dielectrowetting

“…Meirong Song et al (2017) showed that surfactants increase the spreading diameter of water droplets impacting on to superhydrophobic substrates 25 . More recently, Vo et al (2020) and Tan et al (2021), showed that the maximum spreading is augmented by dielectrowetting, while hindering receding and even bouncing 13 , 26 . The contact time of impacting droplets has also been studied extensively.…”

Triggering of electro-elastic anti-superhydrophobicity during non-Newtonian droplet collision

“…Tan et al . [23] revealed the control over drop impact on hydrophobic surfaces based on alternating current electrowetting-on-dielectric (AC EWOD). They studied the impact control mechanism of AC signal on droplets by analysing changes in spread diameter and height under varying frequencies and amplitudes.…”

“…Yun et al [22] investigated and described the mechanism of droplet rebound suppression by inducing non-axisymmetric drop deformation and kinetic energy transfer between orthogonal coordinate axes. Tan et al [23] revealed the control over drop impact on hydrophobic surfaces based on alternating current electrowetting-on-dielectric (AC EWOD). They studied the impact control mechanism of AC signal on droplets by analysing changes in spread diameter and height under varying frequencies and amplitudes.…”

Liquid droplet impact on a sonically excited thin membrane

“…Although several considerable research studies have been conducted to explore impacting droplet characteristics on hydrophobic surfaces, the main focus was to correlate the influence of Weber number, texture characteristics with the spreading and restitution coefficients. 14,15,16 The contribution of the oscillating hydrophobic surfaces to the droplet impacting characteristics has received less attention. The interaction between the droplet fluid and the oscillating hydrophobic surface involves the complicated dynamic process during droplet spreading/retraction and rebounding phases.…”