Smart surface manipulates droplets

Smart surface manipulates droplets

Technology News |
By Rich Pell

The surface’s ability to either repel or absorb liquid – its “wetting behavior” – can be quickly and precisely controlled, say the researchers, resulting in a kind of surface that engineers have long sought to create. Potential applications for such a surface range from water filtration and biomedical devices to liquid optical lenses and lab-on-a-chip systems.

The surface developed by the UBC researchers is claimed to be inexpensive, scalable, and able to be powered by a conventional battery. It has a nanostructured copper surface whose oxidation state – which affects its attraction to water – changes when low voltage is applied.

“When tiny voltages are applied to the surface, water droplets that initially roll off stick to it more and more tightly,” says Ben Zahiri, the co-author of a paper on the research. “By changing the magnitude of the voltage and how long it is applied, we can easily control the angle that each droplet forms with the surface and how quickly this happens.”

Previous attempts at modifying the wetting behavior of copper surfaces have required very high temperatures and prolonged exposure times, making them impractical for many applications. According to the UBC researchers, the wetting behavior of their surface can be modified in a few seconds to minutes using voltages less than 1.5 V.

This ability to control surface wettability could be useful wherever droplets – or solid particles absorbed by droplets – need to be manipulated, including microfluidic devices and hazardous material handling systems. In addition, say the researchers, by enabling the controlled roll-off of fluids, advanced self-cleaning capabilities are possible as well.

The surface will work with any conductive liquid, including blood. Looking beyond their current smart surface, the team believes that the electrochemical manipulation of other metals (besides copper) and metal oxides may offer similar results.

For more, see “Active Control over the Wettability from Superhydrophobic to Superhydrophilic by Electrochemically Altering the Oxidation State in a Low Voltage Range.”

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