Passive "Wearable AC" Cools Without Electricity, Can Hold Complex Circuits for HMI and Biomonitoring

Cooling the wearer wholly passively is just one trick up the sleeve of this smart patch for wearable projects.

Gareth Halfacree
2 months ago β€’ Sensors / Wearables
A clever patch can cool the skin wholly passively, and hold complex circuits too. (πŸ“·: Xu et al)

Researchers from the University of Missouri and the Argonne National Laboratory have developed a new variant of wearable air conditioning, which they claim requires no electricity to operate β€” and could also be used to monitor blood pressure, heart activity, and even hydration.

Taking the form of a breathable and waterproof patch, the on-body cooler don't need electricity to operate β€” a considerable improvement over a similar cooling patch unveiled last year by engineers from the University of California at San Diego, which relied upon a flexible battery pack. Better still: It's possible to extend the functionality of the patch with additional electronics to go beyond cooling to health monitoring and even human-machine interface systems.

"Our device can reflect sunlight away from the human body to minimise heat absorption, while simultaneously allowing the body to dissipate body heat, thereby allowing us to achieve around 11 degrees Fahrenheit of cooling to the human body during the daytime hours," explains co-author Zheng Yan of his team's work. "We believe this is one of the first demonstrations of this capability in the emerging field of on-skin electronics.

"Eventually, we would like to take this technology and apply it to the development of smart textiles. That would allow for the device’s cooling capabilities to be delivered across the whole body. Right now, the cooling is only concentrated in a specific area where the patch is located. We believe this could potentially help reduce electricity usage and also help with global warming."

The secret to the breathable, waterproof, passively-cooling yet potentially multifunctional electronics β€” which, the researchers point out, are both reusable and easily recyclable β€” lies in the spray-painting of silver nanowires onto multiscale porous polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) substrates. Currently, however, extending the patch beyond simple passive cooling requires wires to external hardware; the team is working on a wireless version, which may be ready within the next two years.

The team's work has been published in the journal Proceedings of the National Academy of Sciences (PNAS), and is available in PDF format from the University of Missouri.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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