A team of researchers led by the University of Colorado at Boulder (CU Boulder) has developed a new type of synthetic “leather”. It is slippery like the scales of a snake. The study, published in the journal Applied Materials & Interfaces, focuses on an underestimated problem in engineering: friction.
Every day, different machines – from robots to cars – lose tremendous amounts of energy simply because their parts rub against each other. To mitigate these losses, Yifu Ding, the senior author of the new article, and his colleagues took advantage of nature’s clues to turn their attention to snakes.
“The snake’s body is soft enough to take on a wide variety of shapes,” explains Ding, professor of mechanical engineering at CU Boulder. – Also snakes move very fast if necessary. Partly because of the properties of their skin. “
In their latest study, the scientists developed a solid-liquid interfacial polymerization (SLIP) tool. It allows them to apply a thin layer of skin to existing surfaces – elastomers. For example, rubber. This layer is very similar to the scales of a snake and can turn a sticky surface into a slippery one. The technology is useful for cars that do not tolerate getting wet.
There are many new engineering applications, such as soft robots or wearable sensors, where these traditional liquid lubricants cannot be used. Therefore, scientists came up with the idea of changing the surface itself. Now this is possible thanks to snakes.
Snakes owe much of their glide to scales. If you place one of these small structures under a microscope, you will notice that they are composed of many layers of tissue stacked on top of each other. The top layer is similar to the keratin from which human nails are made. It is very fragile and tough. The scales then gradually transition to the softer material at the bottom. This combination of hard on top of soft gives snakes the advantage of helping them maintain low friction while remaining flexible. It is this function that the scientists wanted to reproduce in the laboratory.
The group started with a backing made from polydimethylsiloxane (PDMS), a resilient material common in many medical technologies. The researchers then applied the SLIP technique to apply a thin, scaly layer of synthetic material to this substrate.
The method works by mixing small molecules with a film of liquid and then using light to force them out of the suspension. Then the building blocks penetrate into the PDMS and form a hybrid skin layer. The result is the laboratory equivalent of snakeskin boots.
The team still has a lot of work to do before it can start applying its slippery surface to the joints of real robots.