April 17th, 2014 | by Michael Keller

Researchers in Switzerland say they have punched precisely shaped holes in films of graphene, a two-dimensional sheet of linked carbon atoms. Their development means graphene, a material that is lightweight and strong, can be made into the thinnest possible membrane with pores of exact size to exclude specific molecules.

Engineers at ETH Zurich created the membrane out of two graphene sheets pressed together. Their prototypes were 100,000 times thinner than a human hair.

“With a thickness of just two carbon atoms, this is the thinnest porous membrane that is technologically possible to make,” said Jakob Buchheim, a nanoscience doctoral student in the university’s Department of Mechanical and Process Engineering. He is a lead author of the study published today in the journal Science.

Along with major applications like filtering water, separating gaseous mixtures and removing impurities from liquids, graphene membranes could be a game changer in rain gear and waterproofing. The researchers say the material could be manufactured to make a coating that excludes liquids while letting gases right on through.

“Our membrane is not only very light and flexible, but it is also a thousand fold more breathable than Gore-Tex,” says Kemal Celebi, the other study lead author and a researcher in the university’s Nanoscience for Energy Technology and Sustainabilitygroup.

Ion drills

In work similar to that being done at MIT, the team improved the hole-punching technique to make their membrane. Graphene’s structure is made of the carbon atoms that link in hexagonal patterns and resemble chicken wire. The researchers made two “drills” that could make differently sized pores in the graphene, which were completely impervious to liquids or gases before being punched. By using a focused beam of helium ions, they could make pores smaller than 10 nanometers. Switching to a drill using a focused beam of gallium ions, they could make holes between 14 nanometers and 1 micrometer in diameter.

And because the membrane is so thin and so densely packed with pores, it allows molecules small enough to fit through the holes to pass very quickly. “With such atomically thin membranes we can reach maximal permeation for a membrane of a given pore size and we believe that they allow the fastest feasible rate of permeation,” said Celebi.

It will still be a while before customers start seeing graphene rain suits for sale at their local department store. The research team says they need to develop and refine the process to get it up to manufacturing scale.

Top Image: via Shutterstock.