Scientists have developed a waterproof wearable patch to detect high level of stress

With the sheer number of people feeling stressed these days, it’s becoming increasingly important to find a way to track and manage stress.

 “The biggest initial challenge was to find a way to sense a neutral molecule (cortisol) with an electrochemical sensor designed to sense charged molecules/atoms,” according to Dr Alberto Salleo, the study co-author and Stanford materials science professor, toInverse. “Onur came up with a sensing layer that blocks ions if cortisol is present.

The device, designed by Onur Parlak Ph.D, a post-doctoral researcher studying materials science and engineering, is a stick-on stretchy patch that measures the levels of cortisol — a hormone produced during stress — in sweat. Of all the compounds in sweat, including potassium and other electrolytes, cortisol is a uniquely special, tricky hormone that’s difficult to track on the surface of the skin. Unlike other elements of sweat, cortisol doesn’t have a positive or negative charge, and so it tends to go undetected by other sweat-sensing wearables, like headbands, which sense electrical charges given off by other molecules.

The waterproof wearable patch, which when applied directly to the skin, absorbs sweat and within seconds assesses how much cortisol stress hormone -- a person is producing.

Clinical tests that measure cortisol, which rises and falls naturally throughout the day, provide an objective gauge of emotional or physical stress  and can help doctors tell if a patient's adrenal or pituitary gland is working properly.

While current methods require waiting several days for results from a lab, with the novel patch, a user just needs to sweat enough to glisten, apply the patch and connect it to a device for analysis, giving the results within seconds.

"We are particularly interested in sweat sensing, because it offers non-invasive and continuous monitoring of various biomarkers for a range of physiological conditions," said lead author, Onur parklak from Stanford University, US.

"This offers a novel approach for the early detection of various diseases and evaluation of sports performance," Parlak added, in the paper published in the journal Science Advances.

If the prototype version of the wearable device  becomes a reality, it could allow people with an imbalance to monitor their own levels at home, the researchers said.

A fast-working test like this may also reveal the emotional state of young, even non-verbal, children who might not otherwise be able to communicate that they feel stress, they noted.

The team developed a stretchy, rectangular sensor around a membrane that specifically binds only to cortisol .Stuck to the skin, it sucks in sweat passively through holes in the bottom of the patch. A waterproof layer protects the patch from contamination.

The sweat pools in a reservoir, which is topped by the cortisol-sensitive membrane.

Charged ions like sodium or potassium, also found in sweat, pass through the membrane unless they are blocked by cortisol. It's those backed up charged ions the sensor detects, not the cortisol  itself.

“Cortisol hormone can be measured by testing blood, saliva or hair but none provide quick results, so are not particularly useful for detecting short-term stressors for quick action,” Parlak tells Inverse. “Sweat provides a non-invasive and quick testing opportunity.”

With this in mind, the team at Stanford will continue to tweak their sweat sensor, looking for ways it can potentially track other molecules. While Fitbit probably won’t attach a sweat patch any day soon, the popularity of fitness and health tracks is illustrative of a larger trend in which people want to know whats happening inside their bodies. A stress-sensing sticker, potentially, is another way in.