The researchers explain: "Graphene oxide sheets arrange in such a way that between them there is room for exactly one layer of water molecules. They arrange themselves in one molecule thick sheets of ice which slide along the graphene surface with practically no friction. If another atom or molecule tries the same trick, it finds that graphene capillaries either shrink in low humidity or get clogged with water molecules."
This membrane can be used to remove water from a mixture or container. The team sealed a bottle of Vodka with such a membrane and this resulted in water evaporating - and the drink became stronger with time.
More info: http://www.sciencemag.org/content/335/6067/442