MIT scientists make sweat-responsive suit, shoe

MIT researchers have designed a breathable workout suit with ventilating flaps that open and close in response to body heat and sweat. The thumbnail-to-finger-sized flaps are lined with live microbial cells that shrink and expand in response to changes in humidity. The team has also fashioned a running shoe with an inner layer of similar cell-lined flaps.

The cells act as tiny sensors and actuators, driving the flaps to open when an athlete works up a sweat, and pulling them closed when the body has cooled off.

Details of both designs have been published in Science Advances. The research was supported, in part, by MIT Media Lab and the Singapore-MIT Alliance for Research and Technology.

The researchers say that moisture-sensitive cells require no additional elements to sense and respond to humidity. The microbial cells they have used are also proven to be safe to touch and even consume. What’s more, with new genetic engineering tools available today, cells can be prepared quickly and in vast quantities, to express multiple functionalities in addition to moisture response.

The researchers engineered moisture-sensitive cells to not only pull flaps open but also light up in response to humid conditions.

“We can combine our cells with genetic tools to introduce other functionalities into these living cells. We use fluorescence as an example, and this can let people know you are running in the dark. In the future we can combine odour-releasing functionalities through genetic engineering. So maybe after going to the gym, the shirt can release a nice-smelling odour,” says Wen Wang, the paper’s lead author and a former research scientist in MIT’s media lab and department of chemical engineering.

Wang’s co-authors include 14 researchers from MIT, specialising in fields including mechanical engineering, chemical engineering, architecture, biological engineering, and fashion design, as well as researchers from new balance athletics. Wang co-led the project, dubbed bioLogic, with former graduate student Lining Yao as part of MIT’s Tangible Media group, led by Hiroshi Ishii, the Jerome B Wiesner Professor of Media Arts and Sciences.

Living things and their components, from pine cone scales to microbial cells and even specific proteins, can change their structures or volumes when there is a change in humidity. The MIT team hypothesised that natural shape-shifters such as yeast, bacteria, and other microbial cells might be used as building blocks to construct moisture-responsive fabrics.

“These cells are so strong that they can induce bending of the substrate they are coated on,” Wang says.

The researchers first worked with the most common nonpathogenic strain of E. coli, which was found to swell and shrink in response to changing humidity. They further engineered the cells to express green fluorescent protein, enabling the cell to glow when it senses humid conditions. They then used a cell-printing method they had previously developed to print E. coli onto sheets of rough, natural latex.

The team printed parallel lines of E. coli cells onto sheets of latex, creating two-layer structures, and exposed the fabric to changing moisture conditions. When the fabric was placed on a hot plate to dry, the cells began to shrink, causing the overlying latex layer to curl up. When the fabric was then exposed to steam, the cells began to glow and expand, causing the latex flatten out. After undergoing 100 such dry/wet cycles, Wang says the fabric experienced “no dramatic degradation” in either its cell layer or its overall performance.

The researchers worked the biofabric into a wearable garment, designing a running suit with cell-lined latex flaps patterned across the suit’s back. They tailored the size of each flap, as well as the degree to which they open, based on previously published maps of where the body produces heat and sweat.

“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,” Yao says. “We redesigned the garment using a fusion of heat and sweat maps to, for example, make flaps bigger where the body generates more heat.”

The team also integrated the moisture-responsive fabric into a rough prototype of a running shoe. Where the bottom of the foot touches the sole of the shoe, the researchers sewed multiple flaps, curved downward, with the cell-lined layer facing toward - though not touching - a runner’s foot. They again designed the size and position of the flaps based on heat and sweat maps of the foot.

The team is looking to collaborate with sportswear companies to commercialise their designs, and is also exploring other uses, including moisture-responsive curtains, lampshades, and bedsheets.