The flow of water on solid surfaces is significantly impeded by frictional forces — which is bad news for, say, marine vehicles. A gas layer can be introduced at the solid–liquid interface as a lubricant, but even slight hydraulic pressure can destroy this layer. Choongyeop Lee and Chang-Jin Kim at the University of California, Los Angeles, have devised a way to keep the gas layer intact and cut drag even in underwater conditions.

The duo began with a highly hydrophobic surface studded with 50-micrometre-high pillars and gold-coated nanostructures (pictured), and submerged this in water. The gold coating allowed an electrolytic reaction to occur, generating gas at its surface when water made contact. Bubbles formed only in areas where there had been no gas before, and because of the surface's architecture, the bubbles spread uniformly across the surface.

Credit: AM. PHYS. SOC.

Phys. Rev. Lett. 106, 014502 (2011)