November 18, 2019

A PITCHER, NOT A GLASS OF WATER:

Superslippery Toilets Squash Water Wastage (Viviane Callier on November 18, 2019, Scientific American)

Now a team of materials scientists at Pennsylvania State University has developed a promising potential solution: an ultraslippery coating that prevents liquid and solid waste from sticking to the toilet bowl, halving the amount of water needed to flush. The researchers say it is more effective than existing hydrophobic, or water-repellent, coatings for toilets, which shed liquid waste well but are less effective for solids. The novel veneer is also antibacterial, which, the researchers say, would reduce a main cause of bathroom odors and lower, by 90 percent, the amount of cleaning material needed to keep toilets sanitary.

"We think this can have a big impact, because everyone needs to use the toilet. And everyone wants the toilet to be clean," says Penn State materials scientist Tak-Sing Wong, senior author of the study, published on Monday in Nature Sustainability. 

The new coating, called liquid-entrenched smooth surface (LESS), consists of two layers. First, researchers spray the inside of the toilet bowl with a silicone material called polydimethylsiloxane, which forms chains of long, stringy molecules known as polymers. The ends of these chains fix themselves to the toilet surface, forming a permanent base layer of "nanohairs." This layer is then sprayed with a silicone oil lubricant about one thousandth of a millimeter thick (roughly half of the length of an Escherichia coli bacterium). The hydrophobic polymers that make up the base layer shed water but attract the silicone oil, keeping the lubricant in place for about 500 flushes (after which more silicone must be applied). The concept was inspired by the carnivorous pitcher plant, which has tubelike modified leaves with slippery interior surfaces that cause unlucky insects to slide into its trap. "One of the key innovations was to use a smooth, lubricated surface, which nature has been using for many years," Wong says.



Posted by at November 18, 2019 1:04 PM

  

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