Uni team in full flow with cheap liquid-repellent material

Local | Sophie Hui 15 Nov 2017

Feel like you're in a spin when washing clothes? Well, it's time to cue the celebrations as a University of Hong Kong research team has created a low- cost material that can repel oil and liquid.

The team, led by Wang Liqiu, of the department of mechanical engineering, worked on the project for about a year, and subsequently created a low-cost liquid-repellent surface that can repel at least 10 types of liquid, including water and oil.

The team was inspired by springtails for their strong mechanical durability and robust liquid-repellency in habitats that often experience rain and flooding.

After being inspired by the structure of the springtails' cuticles, the team designed porous surfaces composed of interconnected honeycomb-like micro- cavities that can enhance mechanical stability through a re-entrant structure for repelling liquid.

One member, Zhu Pingan, said the research team created emulsion that contained oil and water through a microfluidic droplet-based technique. Once they put the emulsion on polyvinyl alcohol after the water and oil evaporated, a porous surface with micro-cavities appeared.

As for the cost, it will be between 70 HK cents to HK$1.30 per square meter - much lower than the liquid-repellent material in the market which hovers around HK$1,000 per square meter.

Wang also said other similar liquid- repellent materials in the market can only repel either water or oil, and they are normally developed via chemical methods and could be toxic.

He also noted that "those kind of chemistry of chemicals normally are not environmental-friendly."

"But our technology used a purely physical method without any chemical modification of our surface," Wang said. "We just used micro and nano structure on the surface to repel various types of liquid, including water, or any other kind of liquid at the same time."

Wang expects the new technology to be applied to items used in daily life, such as clothes and kitchenware, within the next two to three years. There is also potential of the material being used in ships and military equipment in the future.

The team has applied for a patent for the technology.

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