Forces on Drops due to Slide Electrification*

A drop sliding on a water repellent surface acquires a net electrical charge and the counter charges are deposited at the solid surface. This phenomena is known as slide electrification. Slide electrification results in electro-capillarity and hence, alters the solid-liquid and solid-air interfacial energies [1]. The resulting effects contribute to forces on the drop and influence the drop motion [2]. However, the exact mechanisms by which slide electrification affect the drop motion are unclear. In this talk, we quantitatively disentangle the mechanisms by sliding the drop at a defined and constant velocity. We omit the influence of viscous dissipation in the drop and quantify two phenomena: electrowetting due to drop charge and change in solid surface energy due to deposited charges.

(1) Li, X., Ratschow, A. et. al., Surface charge deposition by moving drops reduces contact angles, Phys. Rev. Lett. 131, 228201 (2023).

(2) Li, X., et. al., Spontaneous charging affects the motion of sliding drops, Nat. Phys. 18, 713–719 (2022).