Super Nano-Waterproof Coating Actively Shrugs Off Water, Grease and Would-Be Stains

Shaking It Off

Multilayers of nanoparticles can be used as a coating for cotton fabrics that would actively ward off liquids and stains. The material is stabilized by exposure to UV light.Zhao et al./Langmuir

A new multilayered nanocoating could make future clothes more than just stain-resistant — they'll be stain-offensive, actively sloughing off dirt and gunk to protect the fabric underneath. Instead of merely repelling water or grease, clothing will push them away.

Tong Lin and colleagues at the Australian Future Fibres Research and Innovation Centre at Deakin University wanted to use layer-by-layer (LbL) deposition to form a stable coating of silica nanoparticles. The method alternates positively and negatively charged layers of a material. Previous research has used LbL for sensors and other devices, but the deposition process can be unstable, breaking down in acidic or alkaline environments. To stabilize their compound, Lin and colleagues blasted it with ultraviolet radiation. This anchors the nanoparticles onto the cotton fabric. The method can work with almost any organic substrate, they say. So that means things like wool, coconut or hemp clothing could be waterproofed, too.

The result is a superhydrophobic coating that successfully withstood assault from acids, bases, soaps and solvents and lasted through 50 washing machine cycles. It's more water-repellent than car wax or Teflon, according to the American Chemical Society. This is partly because of the angle of attack on the deposited fabric.

To measure this, the researchers used a scanning electron microscope and a camera at 30 fps to record the action of water droplets. Depending on the number of layers, the contact angles (angle at which droplets reach the surface) reached 152 to 158 degrees, the researchers say. By contrast, Teflon's contact angle is 95 degrees.

The new material is described in the ACS journal Langmuir.

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