A method to create a surface that makes water droplets gyrate when they rebound off it, with rotational speeds exceeding 7,300 revolutions per minute, is described in Nature Communications this week. The findings may have applications in hydro-energy collection, self-cleaning and anti-icing processes.
When a droplet hits a surface, the outcome (if it rebounds or splashes) depends on the structure and chemical properties of the solid. However, owing to the deformability of the droplet and how quickly the interaction between the impacting droplet and solid takes place, it is challenging to manipulate this behaviour.
Yanlin Song and colleagues introduce a chemical patterning method in which high-adhesive spirals are surrounded by hydrophobic (water repelling), low-adhesive regions. When a droplet hits the surface, these patterns induce non-axisymmetric pinning forces (non-symmetrical forces around an axis) which make the droplet gyrate as it rebounds.
The authors suggest that the observed process opens up a promising avenue for the delicate control of liquid motion.