MIT researchers designed athletic clothing that's laden with bacterial cells that enable vents in the garment to automatically open up when you start to sweat. From Smithsonian:
(MIT bioengineer Wen) 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.
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….
One big challenge though is that it doesn't hold up to a wash cycle. Still, Wang says, "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."