Slide electrification

In recent years it has been realized that when water is receding from solid surfaces, electric charges are spontaneously deposited. Water droplets running over a polymer surface, for example, can easily generate voltages of more than 1 kV. This spontaneous charging of surfaces is called contact or slide electrification. It is a reminiscent of tribocharging between solids, but the underlying physical processes are fundamentally different. 

 

In particular, we work on the following topics:

Develop methods to quantitatively measure charging: Rüdiger Berger, Hans-Jürgen Butt

1. Bista, P., A.D. Ratschow, H.-J. Butt & S.A.L. Weber: High voltages in sliding water drops. J. Phys. Chem. Lett. 2023, 14, 11110-11116, DOI: 10.1021/acs.jpclett.3c02864
2. Hinduja, C., H.-J. Butt & R. Berger: Slide electrification of drops at low velocity. Soft Matter 2024, 20, 3349-3358, DOI: 10.1039/D4SM00019F

Analyse the fundamental processes leading to charge separation: Aaron D. Ratschow, Hans-Jürgen Butt

1. Ratschow, A.D., L.S. Bauer, P. Bista, S.A.L. Weber, H.-J. Butt & S. Hardt: How charges separate when surfaces are dewetted. Phys. Rev. Lett. 2024, 132, 2240002, DOI: 10.1103/PhysRevLett.132.224002
2. Bista, P., A.D. Ratschow, A.Z. Stetten, H.-J. Butt & S.A.L. Weber: Surface charge density and induced currents by self-charging sliding drops. Soft Matter 2024, 20, 26, 5045-5052, DOI: 10.1039/D4SM00205A

Demonstrate that the dynamics of wetting, drop motion and drop impact are strongly affected: R. Berger, M. Kappl, K. Koynov, A.D. Ratschow, H.-J. Butt

1. Li, X., P. Bista, A. Stetten, H. Bonart, M.T. Schür, S. Hardt, F. Bodziony, H. Marschall, A. Saal, Xu Deng, R. Berger, S. Weber & H.-J. Butt: Spontaneous charging affects the motion of sliding drops. Nature Physics 2022, 18, 713-719, DOI: 10.1038/s41567-022-01563-6
2. Díaz, D., X. Li, P. Bista, X. Zhou, F. Darvish, H.-J. Butt & M. Kappl: Self-generated electrostatic forces of drops rebounding from hydrophobic surfaces. Physics of Fluids 2023, 35, 017111, DOI: 10.1063/5.0130343
3. Shin, D., R. Lathia, C. Hinduja, H. Cheon, S. Park, H.-J. Butt & J. Park: Salt water drops slide faster: Ionic modulation of drop friction. Advanced Science 2026, 0:e21659, DOI: 10.1002/advs.202521659

Charged solutes are selectively deposited: Kaloian Koynov, Rüdiger Berger, Hans-Jürgen Butt

1. Zhou, X., Y. Ji, Z. Ni, J.G. Lopez, K. Peneva, S. Jiang, N. Knorr, R. Berger, K. Koynov & H.-J. Butt: Spontaneous charging from sliding water drops determines the interfacial deposition of charged solutes. Advanced Materials 2025, 2420263, DOI: 10.1002/adma.202420263

Study the chemical reactions following charge separation: R. Berger, K. Koynov, A.D. Ratschow, H.-J. Butt

1. Ratschow, A., H.-J. Butt, S. Hardt & S. Weber: Liquid slide electrification: Advances and open questions. Soft Matter 2025, 21, 1251-1262, DOI: 10.1039/d4sm01289e