Sweat-monitoring wearables have been a hotbed of research over the last few years. The obvious hurdle for this technology has been the reliance on the body perspiring, meaning the pragmatic usages have been limited to athletes or situations requiring physical exertion. Now a team at the University of Cincinnati (UC) has solved that problem by developing a Band-Aid-sized device that stimulates a body's sweat glands on a small patch of skin.

A huge variety of key chemicals can be now monitored through our perspiration, from diabetics tracking glucose levels to to the fine-tuning of medication dosages by measuring drug metabolite levels. The device developed at UC differs by allowing the biosensor to measure a number of sweat-based hormones and chemicals without a person having to jump on treadmill.

"People for a long time ignored sweat because, although it can be a higher-quality fluid for biomarkers, you can't rely on having access to it," says UC professor Jason Heikenfeld. "Our goal was to achieve methods to stimulate sweat whenever needed — or for days."

The researchers developed a triad of methods to stimulate sweat across a localized region of skin. Initial studies showed that a gel containing a chemical called carbachol, used in eyedrops, was successful in stimulating sweat production. A memory-foam padding was then developed to allow for better contact between the biosensor and the skin.

Finally, the team incorporated a process called iontophoresis, which drives a small amount of the carbachol into the upper layer of the skin using a tiny, imperceptible electric current. The complete process was shown to successfully generate sweat-based sensor results across several days of wearing the device.

The ultimate result of this new innovation could be the development if a wide variety of wearable sweat-based biosensors. Most exciting is the ability to be able to test for minor changes in the levels of certain chemicals or hormones over periods of time in ways that would be simply unfeasible if being tracked through blood samples.

"If you do a blood draw, you get one data point," says Heikenfeld. "In many cases, doctors would love to know if concentrations are increasing or decreasing over time."

The team notes that the US Air Force has displayed interest in the technology for its potential in measuring a pilot's cortisol levels, allowing for near real-time tracking of stress levels in physically and mentally taxing situations. Home health-monitoring after surgery is another potentially useful outcome from the team's innovation.

"It's particularly useful for follow-up visits where normally there is some type of blood testing that has to be done," says UC graduate Zachary Sonner. "They could wear a disposable patch for 20 minutes instead."

The team's research was published in the journal Lab on a Chip.

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