Title: Spontaneous charge separation at the back of sliding water drops

Speaker: Professor Hans-Jürgen Butt（Max Planck Institute for Polymer Research）

Time: 11:00 AM on October 28，2026

Location: C3-c204, GuangzhouInternational Campus,SCUT

Abstract

In the last decade it has been established that water drops sliding over solid surfaces deposit electric charges. Usually, negative charges are deposited at the rear three-phase contact line. The drops themselves acquire the opposite charge. Depending on the specific geometry, electric potentials can easily exceed 1 kV. This liquid analogue to tribocharging is called slide or contact electrification. It substantially reduces contact angles and increases drop friction. The generated electric fields can lead to electric breakdown of the underlying material. Still, the underlying mechanism of slide electrification is not clear and possibly more than one process leads to charge separation.

Speaker Biography

Professor Hans-Jürgen Butt completed his doctoral research at the Max Planck Institute of Biophysics, Germany, in 1989, followed by postdoctoral research at the University of California, Santa Barbara. He subsequently served as Associate Professor of Physical Chemistry at Johannes Gutenberg University Mainz and Full Professor of Physical Chemistry at the University of Siegen. Since 2002, he has been a Director at the Max Planck Institute for Polymer Research, where he heads the Department of Experimental Physics of Interfaces. He is a member of the European Academy of Sciences and served as President of the International Association of Colloid and Interface Scientists (IACIS) from 2018 to 2022. Professor Butt’s research has long focused on interfacial physics and colloid science, with particular emphasis on surface and interfacial forces, particle adhesion and friction, superhydrophobic and superamphiphobic surfaces, and droplet wetting dynamics. He is one of the pioneers of the colloidal probe technique and has made important contributions to thermal noise analysis and cantilever calibration in atomic force microscopy (AFM), providing a methodological foundation for quantitative measurements of surface forces and interactions between colloidal particles. His research has been published in journals including Nature, Nature Materials, Nature Physics, and Physical Review Letters. He has also co-authored Physics and Chemistry of Interfaces and Surface and Interfacial Forces. His distinctions include the Lectureship Award of the Division of Colloid and Surface Chemistry of the Chemical Society of Japan (2011), the Ostwald Prize of the German Colloid Society (2021), the Overbeek Medal of the European Colloid and Interface Society (2022), and an honorary doctorate from the University of Ioannina, Greece (2022). He has also received two European Research Council (ERC) Advanced Grants. In recent years, his group has systematically investigated the fabrication and wetting behavior of superamphiphobic surfaces, three-phase contact line dynamics, and slide electrification, revealing how spontaneous charge separation affects droplet wetting and motion.