A slippery new toilet bowl material is resistant to the stickiness of synthetic poop with different moisture contents. (Video credit: Supplementary Materials from Li et al. 2023 DOI:10.1002/adem.202300703)
An incredibly slippery 3D-printed toilet doesn't get dirty and requires less water to flush than a typical one, scientists say. Could cleaning toilets become a chore of the past?
Right now, the concept is just a prototype, but researchers are working on ways to eventually bring this clever chemistry to market. So far, the researchers have printed only a tiny model of the toilet that stands about one-fifth the height of a typical porcelain throne, and they tested its slickness by exposing its surface to yogurt, honey, starchy gel and fake poop, not the real stuff.
The invention of the flushing toilet revolutionized the way we live, but the innovation came at a cost: namely, 37 billion gallons (141 billion liters) of water flushed per day globally, the researchers wrote in their recent paper, published Aug. 5 in the journal Advanced Engineering Materials. And often, there's another problem: Even all that flushing isn't enough to remove all of the excrement in the bowl.
Bin Su, a principal investigator at Huazhong University of Science and Technology in China, and his team of materials scientists may have found a solution to these problems.
Related: Where does all our poop go?
In their study, the researchers reported that their 3D-printed abrasion-resistant super-slippery flush toilet, or ARSFT, is completely resistant to soiling with various liquids, including milk, muddy water and even synthetic feces. And unlike other slippery toilets, ARSFT maintains its slipperiness even after heavy and repeated use.
The team drew inspiration from tropical pitcher plants (Nepenthes), carnivorous plants that capture prey in vase-like leaf cups; to help channel prey into their traps, the plants secrete a slippery, lubricating substance. Similarly, the researchers coated the toilet's surface in a greasy oil that helped funnel the waste down and out of the bowl.
"When the contaminants fall on to the surface, they first encounter the lubricant film rather than the surface [itself], which can greatly reduce adhesion," the study authors wrote.
On a chemical level, this slippiness originates from a material property called "hydrophobicity," which is a measure of how well the material repels water. Human waste has a high moisture content, so a hydrophobic surface will help prevent poop from sticking.
Using a technique called selective laser sintering 3D printing, the team fused plastic grains and a type of hydrophobic sand to produce the solid shell of the toilet. Sintering is a chemical process that compacts and combines two types of solid without melting them together; importantly, this creates a porous structure with many tiny gaps between the solid particles. The researchers filled these holes using a common lubricating oil that spread throughout the entire structure to coat the whole toilet.
Because the lubricating oil is stored throughout the whole toilet, thanks to the porous structure, any oil lost from the surface is quickly replenished from deeper within the material, enabling the bowl to maintain its super-slippy properties. Even intense mechanical abrasion — like that caused by an overenthusiastic scrub with a toilet brush — doesn't diminish the slipperiness, because the material quickly self-heals by shuffling oil to the newly exposed surface. The team tested this by scrubbing their mini-toilet 1,000 times with sandpaper.
But while the slick new toilet promises to prevent unsightly skid marks on the bowl, it will be a while before you see one of these at your local hardware store.
The team's tiny toilet bowl measured just 3.1 inches (8 centimeters) high, 4.7 inches (12 cm) deep and 3.4 inches (8.8 cm) wide, so it will obviously need to be made bigger. 3D printing can also be notoriously expensive, so producing these toilets cheaply could also be a challenge.
Su's team is already working on these issues. But beyond that, manufacturers would also need to find a way to incorporate the important sintering step into the existing toilet production process. However, there could be uses for this robust nonstick surface beyond toilets, so you may someday see this clever chemistry applied outside the water closet.
