New mesh material captures oil but allows water to pass through
16 April 2015
Ohio State University researchers have developed a stainless steel mesh that lets water pass through but not oil, thanks to an oil-repelling coating on its surface.
The mesh coating is among a suite of nature-inspired nanotechnologies under development at Ohio State. Potential applications range from cleaning oil spills to tracking oil deposits underground.
"If you scale this up, you could potentially catch an oil spill with a net," says Ohio's Professor Bharat Bhushan.
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.
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 of this. The coating is only a few hundred nanometres thick.
The silica, surfactant, polymer, and stainless steel are all non-toxic and relatively inexpensive, and Brown estimates that a larger mesh net could be created for less than one US 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 percent 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-percent range," Bhushan said. "In all our coatings, different combinations of ingredients in the layers yield different properties. The trick is to select the right layers."
He explained that certain combinations of layers yield nanoparticles that bind to oil instead of repelling it. Such particles could be used to detect oil underground or aid removal in the case of oil spills.