Engineering a microbe-driven moisture-responsive workout suit Monday, 22 May 2017

Researchers at MIT have designed a workout suit with ventilating flaps that open and close in response to the athlete's body heat and sweat.

However, unlike conventional wearables, the breathable workout suit's ventilating flaps are lined with live microbial cells that shrink and expend in response to changes in humidity, effectively acting as tiny sensors and actuators, driving the flaps to open when the athlete works up a sweat, and pulling them closed when the body has cooled off.

The bioLogic team includes 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.

Wen Wang, a former research scientist in MIT's Media Lab and Department of Chemical Engineering, co-led the project. According to him, the choice to use microbial cells was due to the fact that they require no additional elements to sense and respond to humidity.

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

The cells are also proven to be safe to touch and even consume, and with genetic engineering tools available today, cells can be prepared quickly and in vast quantities, and can also function differently to moisture. For example, the researchers have created moisture-sensitive cells that not only pull flaps open but also light up in response to humid conditions.

"This can let people know you are running in the dark," explained Wang. "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."

The team were inspired by the fact that in nature, living things and their components, from pine cone scales to microbial cells and even proteins, can change their structures or volumes in response to changes in humidity. They hypothesised that natural shape-shifters can be used as building blocks to construct moisture-responsive fabrics.

The researchers started with a common nonpathogenic strain of E. coli, which swells and shrinks in response to changing humidity. They modified the cells to express green fluorescent protein, so it glows in humid conditions.

They then used a cell-printing method to print E. coli onto sheets of rough, natural latex in two-layer structures. 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. They tested the material over 100 dry-wet cycles and found the fabric experienced no dramatic degradation in either its cell layer or its overall performance.

The team then 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.

Support frames underneath each flap keep the fabric’s inner cell layer from directly touching the skin, while at the same time, the cells are able to sense and react to humidity changes in the air lying just over the skin. In trials to test the running suit, study participants donned the garment and worked out on exercise treadmills and bicycles while researchers monitored their temperature and humidity using small sensors positioned across their backs.

After five minutes of exercise, the suit’s flaps started opening up, right around the time when participants reported feeling warm and sweaty. According to sensor readings, the flaps effectively removed sweat from the body and lowered skin temperature, more so than when participants wore a similar running suit with nonfunctional flaps.

[Nominations are now open for the Engineers Australia David Dewhurst award and Women in Biomedical Engineering Scholarship. Find out more.]