The relatively simple phenomenon of a sliding drop on a surface is far from quantitatively understood, according to Professor Dr Hans-Jürgen Butt at the latest City University of Hong Kong (CityU) Institute for Advanced Study (IAS) Distinguished Lecture, which was held on 15 May. 
 
At the lecture, titled “Wetting: A Multiscale Phenomenon”, Professor Butt said one reason for the lack of understanding was that macroscopic wetting was determined by processes at very different length and time scales. In particular events at the contact line, where solid, liquid and air meet, influence drop movement. 

Professor Butt has led the group for Experimental Physics of Interfaces as a director at the Max Planck Institute for Polymer Research, Germany since 2002. The group aims at describing processes at interfaces quantitatively.