New mesh captures oil, lets water through

Researchers, including one of Indian-origin, have developed a mesh that allows water to pass through but not oil, an advance that may allow for cleaning of oil spills for less than USD 1 per square foot.
The mesh, developed by Ohio State University researchers, contains a nearly invisible oil-repelling coating on its surface.
In tests, researchers mixed water with oil and poured the mixture onto the mesh. The water filtered through the mesh to land in a beaker below. The oil collected on top of the mesh, and rolled off easily into a separate beaker when the mesh was tilted.

"If you scale this up, you could potentially catch an oil spill with a net," said Bharat Bhushan, Ohio Eminent Scholar and Howard D Winbigler Professor of mechanical engineering at Ohio State.
The work was partly inspired by lotus leaves, whose bumpy surfaces naturally repel water but not oil.
To create a coating that did the opposite, Bhushan and postdoctoral researcher Philip Brown chose to cover a bumpy surface with a polymer embedded with molecules of surfactant - the stuff that gives cleaning power to soap and detergent.

They sprayed a fine dusting of silica nanoparticles onto the stainless steel mesh to create a randomly bumpy surface and layered the polymer and surfactant on top.

The silica, surfactant, polymer, and stainless steel are all non-toxic and relatively inexpensive, said Brown. He estimated that a larger mesh net could be created for less than a dollar per square foot.
The researchers chose silica in part because it is an ingredient in glass, and they wanted to explore this technology's potential for creating smudge-free glass coatings.
At 70 per cent transparency, the coating could work for certain automotive glass applications, such as mirrors, but not most windows or smartphone surfaces.
"Our goal is to reach a transparency in the 90-per cent range," Bhushan said.
The research is published in the journal Nature Scientific Reports.