Athletic wear often claims to allow ventilation or drain away sweat. Thanks to new inventions by UC Davis engineers, future clothing might actually respond to sweat by opening vents or relaxing constrictions. 

The invention is the latest from the Micro-Nano Innovations (MiNi) Laboratory at UC Davis, headed by Tingrui Pan, professor of biomedical engineering.

The invention is based on the different ways fabrics can respond to wetting. Postdoctoral researcher Yahui Yang bonded patterns of waterproof fabric to a piece of cotton fabric.

When cotton gets wet, it expands in volume, but the nonwettable fabric does not expand when exposed to water. Yang found that by sticking the two together, he could create shapes that curl up when they get wet and relax again as they dry out.

Many materials expand or contract in response to heat or humidity. Stick two metals together that expand at different rates in response to heat, and you’ve made a simple thermostat. But this is the first time this principle of mechanical expansion has been applied to do something useful with fabrics, or with water-driven rather than thermal expansion, Pan said.

“By opening up these vents in the fabric as you exercise, you can bring in more air flow,” Pan said. 

Yang experimented with different patterns and sizes of cuts in the wettable fabric. He found that with smaller cuts, he could get the stiffer fabric to act as a cantilever, concentrating force in a particular area.

“Just a few percent of expansion can give you a lot of movement,” he said.

UC Davis has filed a provisional patent, and Pan said that they are already in discussions with companies about the technology.

The work was partly supported by grants from the National Science Foundation and the National Institutes of Health.