Engineers at Purdue University in Indiana have developed a method to transform existing cloth items into battery-free wearables resistant to laundry.

These smart clothes are powered wirelessly through a flexible, silk-based coil sewn on the textile.

In the near future, clothes will become smart, checking on the wearer’s health status and even calling for help if the wearer is in an accident.

These smart cloths should outperform conventional passive garments, thanks to their miniature electronic circuits and sensors, which will allow seamless communications with smartphones, computers, cars and other machines.

The reason why this smart clothing is not being used in the mass market is that the fabrication of this clothing is quite difficult, as clothes need to be periodically washed and electronics despise water.

Purdue engineers have developed a spray and sewing method to transform any conventional cloth items into battery-free wearables that can be cleaned in the washing machine.

“By spray-coating smart clothes with highly hydrophobic molecules, we are able to render them repellent to water, oil and mud,” said Ramses Martinez, an assistant professor in Purdue’s School of Industrial Engineering. “These smart clothes are almost impossible to stain and can be used underwater and washed in conventional washing machines without damaging the electronic components sewn on their surface.”

This research was published in the May 25 edition of Nano Energy.

The rigidity of typical waterproof garments and their reduced breathability make them feel uncomfortable after being worn for a few hours.

“Thanks to their ultrathin coating, our smart clothes remain as flexible, stretchable and breathable as conventional cotton T-shirts,” Martinez said.

Unlike common wearables, the Purdue smart clothes do not require batteries for powering. By simply harvesting energy from wifi or radio waves in the environment, the clothes can power the circuitry sewn on the textile.

One example is a battery-free glove that illuminates its fingertips every time the user is near a live cable to warn about the possibility of an electric shock. Another is a miniature cardiac monitoring system sewn on a washable sweatband capable of monitoring the health status of the wearer.

“Such wearable devices, powered by ubiquitous wifi signals, will make us not only think of clothing as just a garment that keeps us warm but also as wearable tools designed to help us in our daily life, monitor our health and protect us from accidents,” Martinez said. “I envision smart clothes will be able to transmit information about the posture and motion of the wearer to mobile apps, allowing machines to understand human intent without the need of other interfaces, expanding the way we communicate, interact with devices and play video games.”

This technology can be fabricated in conventional, large-scale sewing facilities, which are expected to accelerate the development and commercialisation of future smart clothes.