Dresden 2020 – scientific programme

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O: Fachverband Oberflächenphysik

O 116: Wetting and Liquids at Interfaces and Surfaces II (joint session CPP/DY/O)

O 116.1: Invited Talk

Friday, March 20, 2020, 09:30–10:00, ZEU 260

Slide electrification: charging of surfaces by moving water drops — •Hans-Jürgen Butt — Max Planck Institute for Polymer Research, Mainz, Germany

Water drops sliding over insulating surfaces can lead to surface charging. In contrast to charging caused by friction between two solids, drop slide electrification is largely unexplored. Slide electrification has been consistently reported, but results are difficult to reproduce. One reason for the lack of quantitative understanding is that the deposition of charge is a non-equilibrium effect and depends essentially on microscopic processes at the contact line. We address both the experimental and theoretical sides of this problem. We reproducibly measure the charge gained by water drops sliding down hydrophobic surfaces. To explain these results, we theorize that some fraction of the charge in the Debye layer is transferred to the surface rather than being neutralized as the drop passes. Given that nearly every surface in our lives comes in contact with water, this water-dependent surface charging may be a ubiquitous process that we are only beginning to understand.