Stressed Out? This Wearable Can Tell

Medical Design Briefs INSIDER

A new wearable biosensor, developed by the Salleo lab at Stanford, measures the amount of cortisol in a person’s sweat. (Image credit: Getty Images)

A stretchy patch, applied directly to the skin, wicks up sweat and assesses how much cortisol — the stress hormone — a person is producing. To see cortisol levels, all a user needs to do is sweat (enough to glisten), apply the patch, and connect it to a device for analysis, which gives results in seconds.

Clinical tests that measure cortisol provide an objective gauge of emotional or physical stress in research subjects and can help doctors tell if a patient’s adrenal or pituitary gland is working properly. 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. A fast-working test like this could also reveal the emotional state of young — even non-verbal – children, who might not otherwise be able to communicate that they feel stress.

The 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. 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. On top of all this is a waterproof layer that protects the patch from contamination.

So far, the sensor appears to work as designed. But the researchers want to make it more reliable and accurate, and also make sure it is reusable. The prototype seems to work multiple times so long as it is not saturated with sweat. In the future, they may try the cortisol sensor on saliva, which would avoid patients needing to sweat.

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