It’s an incredibly unappealing combination: sweat and bacteria. But if these MIT researchers have their way, you’ll want them mixing in a place you’d normally try to keep clean and dry: your feet.
Or, more specifically, your running shoes. In a new paper published in Science Advances, researchers at the MIT Media Lab’s Tangible Media group show how specialized bacteria that swells and shrinks based on humidity can be used to make clothing and shoes. That means your gear would actually respond to your sweat, as the bacteria’s movement pushes vents in the fabric open and closed.
The project, which is called bioLogic, got started by focusing on clothing applications–and won a 2016 Innovation By Design award for it. But a running shoe is a new application of the technology, which is evolving to include other functionality.
Now, instead of using the bacteria in its natural state, the team is able to genetically modify it so that it glows as well as expands when there’s enough humidity. “You can now consider bacteria as a programmable interface,” says Lining Yao, one of the lead researchers on the project. “You can define any inputs and any outputs. It could be actuation, it could be glowing.”
The bacteria–called Bacillus subtilis natto–lives inside of dry rice stalks and was discovered 1,000 years ago by a Japanese samurai who realized its presence could ferment soybeans. For hundreds of years, it was used to make the Japanese dish Nattō before these scientists decided to grow it to create actuators that are activated by sweat.
Yao says that the researchers have created two designs for the shoe. The first is based on the fact that the bottom of feet sweat the most, so the ventilating flaps are located along the insole of the shoe. The second has flaps covering the entire foot in order to better demonstrate how lighting intensity changes in the dark as the amount of sweat increases.
While the researchers’ two shoe prototypes currently only use the bacteria to open the ventilation flaps and to glow (a useful trick if you’re running when it’s dark out), it could also be bioengineered to have other functions as well, like changing colors or emitting smells.
Finding a way to keep the bacteria alive when they’re applied to the textile is the next step in the project because living bacteria increase the amount of activity that the scientists can utilize. In particular, Yao says that if the bacteria are metabolically active, they can generate smells; just imagine if your shoes could self-generate a scent as they get sweatier. “For the current version we do not purposely keep the bacteria alive on the fabric once it’s applied, but we want to do that so you have a real growing garment,” she says.
Another area of interest is in finding a way to weave the bacteria into a fiber that could be woven or knit into other garments. Then it would fit within already established manufacturing processes, speeding up how quickly living, growing garments and shoes could be ready for consumers.
So while today you’d likely never voluntarily want to cloak your sweaty feet with bacteria, with the right engineered materials the combination might be too tempting to pass up.