US Patent 7323033 - Variable permeability surface using nanoposts

http://www.freepatentsonline.com/7323033.html

This patent from Lucent teaches using nanoposts to maintain a fluid separated from a porous membrane. Application of a voltage can be used to control the surface tension of the fluid and create a variable permeability membrane. Applications include controlling the electrolytic fluid in a battery to preserve battery life and controlling the breathability and water resistance of fabrics. Claim 1 reads:

1. Apparatus comprising: a substrate having a plurality of openings; and a plurality of nanostructures disposed on a surface of said substrate, the plurality of nanostructures being able to suspend a fluid above the surface without the fluid contacting the surface, wherein said plurality of openings are disposed between at least a portion of the nanostructures in a way such that at least a portion of said fluid passes through said plurality of openings when the fluid is caused to penetrate the plurality of nanostructures and contact the substrate.