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Scientists invent slippery water-saving toilet coating

A new slippery coating promises to dramatically reduce the amount of water needed to flush a toilet.

With more than 141 GL of water used to flush toilets around the world each day, scientists from Penn State University in the United States asked the question: what if poo didn’t stick?

They designed a liquid-entrenched smooth surface (LESS) coating that can be applied to a ceramic toilet bowl to help ease excrement on its way. This is a dual-step process consisting of two sprays, which takes less than five minutes to set.

Doctoral graduate and co-developer Jing Wang said the first spray helps to build an extremely smooth and liquid-repellent foundation.

“When it dries, the first spray grows molecules that look like little hairs, with a diameter of about 1 million times thinner than a human’s,” he said.

The second spray then infuses a thin layer of lubricant around the nanoscopic hairs to create a super-slippery surface. 

“When we put that coating on a toilet in the lab and dump synthetic fecal matter on it, [the synthetic matter] just completely slides down and nothing sticks to [the toilet],” Wang said.

The researchers said the slippery surface means toilets can be cleaned effectively with a fraction of the water usually needed. 

They also found the surface effectively repels bacteria, particularly those that spread infectious diseases and unpleasant smells.

Tak-Sing Wong, associate professor of mechanical engineering and biomedical engineering at Penn State said the technology could have a positive impact in developing countries

“Poop sticking to the toilet is not only unpleasant to users, but it also presents serious health concerns,” Wong said.

“Our team has developed a robust bio-inspired, liquid, sludge- and bacteria-repellent coating that can essentially make a toilet self-cleaning.”

Wong, Wang and collaborators Birgitt Boschitsch and Nan Sun, all Penn State engineering alumni, have now created a start-up, spotLESS Materials, to bring the technology to market.

“As a researcher in an academic setting, my goal is to invent things that everyone can benefit from,” Wong said.

“To maximise the impact of our coating technology, we need to get it out of the lab.”