Gym clothes are generally made to be breathable, but now a team at MIT has developed a material to make activewear truly active when it comes to keeping cool. The outfit is made out of a living "biofabric" full of microbial cells, which automatically open flaps in the shirt when they sense heat and sweat.
We've seen sports bras and ski jackets that open vents like this, but in those cases, the brains of the operation were microprocessors. Here the MIT team has harnessed the humidity-sensing ability of non-pathogenic E. coli cells, and to make them easier to see, they also engineered the cells to fluoresce green when they sensed moisture.
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To make their biofabric, the researchers "printed" lines of E. coli onto sheets of latex, attached them to a second layer with no microbes and tested the material's responses to humidity in the lab. Segments heated on a hot plate would curl up and open flaps in the top layer, and when exposed to steam, the cells would do the opposite, expanding and flattening out the flaps.
Then the team created a running shirt out of the material, with these cell-controlled flaps all across the back. The support layer underneath keeps the microbes from coming into contact with the wearer's skin, while still allowing them to sense the humidity coming off them. To determine how big each flap should be and how far it should open, the team used existing maps of which parts of the body generate the most heat and sweat – two different but related metrics.
"People may think heat and sweat are the same, but in fact, some areas like the lower spine produce lots of sweat but not much heat," says Lining Yao, co-lead author of the study. "We redesigned the garment using a fusion of heat and sweat maps to, for example, make flaps bigger where the body generates more heat."
Thanks to the cells, the biofabric bends in response to moisture, which opens the flaps and cools the wearer as they sweat (Credit: Chin-Yi Cheng)
To test the garment, the researchers had participants work out on treadmills and exercise bikes while they monitored the temperature and humidity of their skin. Right on cue, the flaps began opening after about five minutes, which correlated with the time the exercisers started feeling a bit warm. Compared to sessions in clothes without the flaps, the sensors showed that the biofabric worked well in removing sweat and cooling the participants down.
The team also experimented with putting the material into the soles of running shoes to remove moisture and heat, which could also reduce the risk of conditions like warts. In future, the researchers say they could look into making curtains, packaging and bedsheets that react to moisture, as well as engineering the cells to help out in other ways.
"We can combine our cells with genetic tools to introduce other functionalities into these living cells," says Wen Wang, lead author of the paper. "We use fluorescence as an example, and this can let people know you are running in the dark. In the future we can combine odor-releasing functionalities through genetic engineering. So maybe after going to the gym, the shirt can release a nice-smelling odor."
The research was published in the journal Science Advances. The biofabric can be seen in action in the video below.