Ultrafast microscopy of sliding droplets

The motion of liquid droplets on solid surfaces is governed by processes occurring at the moving contact line and plays a key role in wetting, friction, and interfacial transport.
We have developed an ultrafast reflection microscopy setup to directly visualize sliding droplets and contact line dynamics with high spatial and temporal resolution. These studies are complemented by confocal laser scanning microscopy and fluorescence correlation spectroscopy to correlate droplet dynamics with interfacial structure and molecular mobility.
Our work addresses the microscopic origins of lateral adhesion and friction during sliding and explores how surface heterogeneities and electrostatic effects influence droplet motion, including slide electrification and its consequences for interfacial processes.

 

For example, using our ultrafast reflection microscopy setup, we track how sliding water droplets interact with isolated surface defects. We observe that a defect becomes charged by the passage of the first droplet and subsequently attracts the following droplets, illustrating the role of slide electrification in droplet–defect interactions.