Issue 8, 2022

Charging of drops impacting onto superhydrophobic surfaces


When neutral water drops impact and rebound from superhydrophobic surfaces, they acquire a positive electrical charge. To measure the charge, we analyzed the trajectory of rebounding drops in an external electric field by high-speed video imaging. Although this charging phenomenon has been observed in the past, little is known about the controlling parameters for the amount of drop charging. Here we investigate the relative importance of five of these potential variables: impact speed, drop contact area, contact line retraction speed, drop size, and type of surface. We additionally apply our previously reported model for sliding drop electrification to the case of impacting drops, suggesting that the two cases contain the same charge separation mechanism at the contact line. Both our experimental results and our theoretical model indicate that maximum contact area is the dominant control parameter for charge separation.

Graphical abstract: Charging of drops impacting onto superhydrophobic surfaces

Supplementary files

Article information

Article type
04 Dec 2021
19 Jan 2022
First published
24 Jan 2022
This article is Open Access
Creative Commons BY license

Soft Matter, 2022,18, 1628-1635

Charging of drops impacting onto superhydrophobic surfaces

D. Díaz, D. Garcia-Gonzalez, P. Bista, S. A. L. Weber, H. Butt, A. Stetten and M. Kappl, Soft Matter, 2022, 18, 1628 DOI: 10.1039/D1SM01725J

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