A shirt with millions of bacteria can’t be all bad, right?

Bioengineer Wen Wang thought it was such a good idea that she invented an athletic-wear fabric that incorporates bacteria-activated vents to cool down the wearer.

She got the inspiration in 2013 when, as a research scientist at the Massachusetts Institute of Technology, she listened to a presentation about how Bacillus (bacteria found in soil and vegetation) spores shrink in response to falling relative humidity. That made her wonder if this biological process could be used to develop a material that would ventilate upon sensing the sweat of its wearer.  

“Humans are a natural source of humid air,” says Wang, a researcher at MIT's Media Lab. “We thought maybe we can do something related to garments.”

Wang teamed up with designer Lining Yao to explore the idea further. Their research showed that whole bacteria respond better to moisture compared to the spores. When it came time to prototype the fabric, Wang chose to use whole bacteria, in part because they are so easy to produce. “One bacterium, overnight, becomes millions,” adds Wang.

A New Class of Clothing

Wang’s idea was to create bacteria-laden vents in an exercise shirt that would remain closed when there was no humidity, but open up in response to humidity (sweat).

Wang’s team 3D-printed a layer of bacterial cells directly on both sides of latex sheets. This way, both sides would respond equally to room conditions, and the fabric would remain flat. But when one side was exposed to humidity (for example, the inside of a shirt during exercise), that side would expand relative to the opposite side, and the material would bend outward, forcing the vents open. The bacterial cells range from one to five microns thick (about the diameter of a red blood cell) and one-fifteenth the width of a human hair. 

Wang used a prototype of triple-layer fabric made with Bacillus subtilis to create vents on the back of a shirt. The placement of the vents was determined using heat and sweat maps of the body, so that bigger flaps were placed where the body releases the most heat.

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Volunteers wore the shirt while running on a treadmill or cycling on a stationary bike. After about five minutes the vents opened, allowing the sweat to evaporate and reducing the body temperature of the volunteers.

“When I wore it, once I started to sweat, it opened very naturally and I could feel air flow come to my back,” said Wang. “That’s the advantage of this garment—it helps remove the moisture immediately [through evaporation], which allows the body temperature to drop.”

When this happens, the relative humidity equalizes on both sides of the garment, and the flaps close again. The shirt itself does not absorb the sweat and remains dry.

Future Possibilities

Wang and her team are exploring how whole bacteria can be combined with fabrics to consume sweat, emit light for exercising at night, or producing pleasant-smelling odors.

Although Bacillus subtilis is safe enough to be used in food, Wang thinks that some potential users will be turned off by the idea of bacteria in their clothing.

“Some people might fear the bacteria would contaminate their homes or sicken their children,” Wang says. “Our skin is not a vacuum. If we have no bacteria on it, it will have some bad bacteria on it. In the future we want to combine microbiome technology with our current design to make microbiome-carrying garments.” The team also thinks that other microbes, such as yeast and smaller cellular components like proteins, could perform equally well, without having the stigma that bacteria carries. 

Wang is quick to mention that her research benefitted greatly from working with industry partners, especially New Balance. Right now they are exploring how to commercialize her prototype, including making the garment washable by having the bacteria or cellular materials bind covalently to the latex.

“Collaborating with industry partners has been vital to our research,” she says. “They understand the needs of customer and the technical challenges in the industry. Their participation has helped us further improve the performance of our design, especially when considering industry needs and process feasibility.”

Mark Crawford is a technical writer based in Madison, WI.

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