Roughen by stretching

Elastic, lubricated surfaces that, when deformed, change their transparency, erase fingerprints on them or stop droplets from sliding, are reported online this week in Nature Materials.

Joanna Aizenberg and colleagues created elastic nanoporous thin films and infused them with a liquid that is able to wet the pores. They show that when the liquid completely fills the pores and overcoats the films, these become fairly transparent and their surface is smooth and slippery. When the film is stretched, however, the liquid coating the film recedes into the expanded pores, exposing their edges and reducing lubrication, and thus making the film’s surface rough. The researchers demonstrate that the degree of surface roughness, and therefore its level of water-repellency and transparency, can be easily readjusted by stretching the films or letting them relax. This can be done at any desired area of the surface by, for example, poking it with a finger or bending it with the hands.

The authors suggest that these adaptative, fluid-infused nanoporous films could inspire the design of materials that, for example, become opaque or water repellent in response to light or rain.