When things stick together in life and you don’t want them to stick together, bad things can happen. You get nasty bacteria building up on medical equipment. You get “marine fouling” burrowing into the bottom of ships and oil rigs. You get ice accreting to freezers, messing up their works.
Sticky situations like these can be costly, and even dangerous–but perhaps not for much longer. A new generation of materials could radically reduce unwanted stickiness and solve lots of problems. The technology is called SLIPS–or Slippery Liquid-Infused Porous Surfaces.
Developed at Harvard University’s Wyss Institute for Biologically Inspired Engineering, SLIPS is good at repelling all kinds of liquids because, in a sense, it is a liquid. SLIPS surfaces are made to be “unstructured” so they incorporate a very thin liquid top layer. That makes them different from current superhydrophobic materials that rely on a layer of air to keep water at bay.
“What’s different about our approach is that it’s applicable to any type of dangerous material,” says Joanna Aizenberg, the professor behind the technology. “It repels oils, ice, blood, and bacteria. Traditional hydrophobic surfaces actually perform worse when you get to marine fouling or ice buildup.”
So far, Aizenberg and her team are yet to find a single thing that will stick to one of their surfaces, including several nonliquids. What’s more, the SLIPS surfaces are also self-healing. If you cut into a piece of coated metal, for instance, the upper layer will seep into the porous area that opens up, protecting against accidents. And, SLIPS surfaces seem to work as well in extreme temperatures as temperate ones.
Aizenberg, who’s been working on hyper-repellent materials for more than 20 years, started on SLIPS in 2008. Her inspiration: pitcher plants (see photo) that, through the slipperiness of their funnels, capture insects for food. That and the human body, which effortlessly regulates its surfaces through the miracle of mucus.
Last year, Aizenberg set up a company, SLIPS Technologies, to commercialize her work. The first applications are likely to be in nonhuman situations–like greasing the insides of oil pipelines–rather than things closer to the human body that require more regulatory approval.