Nanorods may soon afford us the abilities of water striders, according to a research paper published in Nature Materials. The authors of the paper are trying to develop a surface with a grain that's produced by thousands of tiny nanorods, all pointing in a single direction. A surface covered with these rods can both grip the water in a certain direction and force the water to roll off it in different direction. This works even when the surface experiences random vibrations, and could be used to reduce drag on plane or ship surfaces and in microfluidics devices.

Anisotropic wetting surfaces, or surfaces that only allow water to roll across them in one direction without getting absorbed, appear on lots of organisms. Water striders use their grained feet to push across water. Butterflies' wings are also grained so that, no matter the motion of the wing, the water rolls off in only one direction and isn't easily absorbed. Researchers have been trying to imitate this sort of texture for some time, but had not had much success in creating one that worked as well as natural ones.

In the new paper, a team describe a surface textured with nanorods made from a polymer, structured like rows of combs pointed at an angle. The nanorods have blunt surfaces and are oriented at an optimal direction so that when the surface is vibrated, even in random directions, water droplets roll away in only one direction without slippage in the other direction.

This sort of surface could be used in microfluidics devices, where options to propel water are limited; random vibrations and nanorods could stand in for a tiny pump. It could also help decrease drag on surfaces that are subject to unusual fluid flow, as when air or water flowing over a surface gets caught in a whorl. Oriented in the opposite direction, the rods could be used to grip water surfaces, if needed.

We wouldn't say no to some anisotropic wetting shoes. Size nine.

Nature Materials, 2010. DOI: 10.1038/NMAT2864 (About DOIs).