Most of the things we encounter in daily life are extremely static, or at least unresponsive, compared to the way living things work. That’s true for clothes: You put them on, they stay on, and if you want them to change you unzip zippers or undo buttons.
But a new class of workout clothing leverages living bacteria, which expand when exposed to moisture and contract when dehydrated. Developed by a multidisciplinary team at MIT in collaboration with athletic-wear company New Balance, the clothes have vents that open automatically as the wearer starts to sweat.
The clothes, and the technology used to produce them, are described in a paper published in Science Advances, which also discusses several other new techniques that could expand potential uses for the technology, by introducing new microbes or genetically altering them.
Wen Wang, an MIT bioengineer, headed up the biotechnology and materials science for the study. (Other collaborators included designers and architects, engineers, and industry experts from New Balance.) Wang and her team explored a number of different applications before focusing on clothing. (Another paper by the team described similar technology used to fold flat pasta-like food into three-dimensional shapes when it is dunked in hot broth, like a self-assembling IKEA flat-pack meal.)
With textiles, Wang and her team found the optimal construction was a layer of latex sandwiched by two thin layers of bacterial cells, each 1 to 5 microns thick, around the diameter of a red blood cell and 1/15th the width of a human hair. These were formed into flaps, and attached to the back of a workout garment. When the wearer sweats, the cells on the outside remain the same, but the cells on the side facing the body absorb moisture and expand, forcing the flaps open.
The MIT Media Lab’s bioLogic group, which Wang and her collaborators are part of, has been building this sort of clothing for a couple of years. But Wang felt there was room for improvement; initially, they used a bacteria called Bacillus subtilis natto, better known as the main component of the gooey, stringy, pungent Japanese food called nattō. Ozgur Sahin, an associate professor of biological sciences and physics at Columbia University, has been using B. subtilis natto in his (unrelated) research into bacteria-using materials because of its tough, strong spores. Wang adopted it because she saw it worked, and because it’s safe enough to be used in food. But still, she thinks potential users might be turned off by having bacteria in their clothing.
“Some people might be afraid that the bacteria may contaminate my home, or my kids,” says Wang, though she emphasizes the microbe's safety. “Our skin is not a vacuum. If you have no bacteria on it, it will have some bad bacteria on it. So in the future, we also want to combine microbiome technology with our current design to make a microbiome-carrying garment."
The paper also describes using other microbes, including yeast and smaller cellular components like proteins, to perform similar functions that might not carry the stigma of bacteria. All of the microbes, points out Wang, are in a vegetative state where they are not growing or dividing, and thus require no food or sustenance.
Finally, the team introduced fluorescence into the bacteria to prove that they could genetically modify it, to expand potential future applications, including microbes that emit a pleasant smell. “It would be easy to incorporate other genetically engineered microbes into this garment as well,” says Wang.
Don’t expect to see these garments in the New Balance store soon. Although the team has applied for a patent for the technology, they have yet to demonstrate its durability through wash cycles.
“Longer term studies could be necessary to find out what might go wrong. I don’t see that being a fundamental challenge, but once you identify them you can spend time addressing it,” says Sahin, who was not involved in the study. “If this is a wearable material, then it should resist friction, for example, with the skin. It should resist washing, maybe the chemicals that are used in washing detergents, for example. Sweat itself might have effects beyond opening and closing the vents.
"This kind of thinking, that cloth can actually be dynamic and responsive, and that response is better for its functions, is generally an exciting aspect of the work, and it can potentially be applied in many other areas.”