‘Most slippery surface ever’ inspired by new understanding of surface roughness

The slipperiness of a surface can be tuned by tweaking its molecular-scale roughness, researchers in Finland have shown. This helps to explain why water droplets can easily slide off hydrophilic surfaces if they are chemically homogeneous, and also opens up new possibilities for the design of low-friction surfaces – allowing the researchers to produce what they believe is the most slippery surface ever created.

The slipperiness of surfaces is sensitive to topographic heterogeneity or roughness and some studies have shown that this sensitivity persists all the way down to the molecular level. Nevertheless, droplets do not readily slide on most hydrophilic surfaces, with some exceptions such as those based on polyethylene glycol. ‘There are just a few reported, but [researchers] don’t really explain the origin,’ says Robin Ras at Aalto University.