Wearable device can measure cortisol in sweat

A research team led by Alberto Salleo, material scientist from Stanford University, has recently created a patch that can measure the cortisol levels in sweat when applied directly to the skin. The paper describing the device was published recently in the journal Science Advances.

Cortisol levels do not stay consistent throughout the day and can increase or decrease as a reaction to external and internal stimuli. Current laboratory tests for measuring cortisol levels take up days and till then, a person’s cortisol level usually is different from what might have during the test. This makes diagnostic assessments quite difficult.

Onur Parlak, a post-doctoral scholar working in Salleo’s lab and also the lead author of the paper said, “We are particularly interested in sweat sensing, because it offers noninvasive and continuous monitoring of various biomarkers for a range of physiological conditions. This offers a novel approach for the early detection of various diseases and evaluation of sports performance.”

Cortisol levels can tell doctors a lot about emotional or physical stress that their patients might be going through and if their adrenal and pituitary glands are working like they should. Although only a prototype is available currently, but once turned into reality, the device will let people measure their cortisol levels at home.

Salleo and Parlak knew about the challenge that cortisol poses to biosensors like the one they have developed. Because cortisol is chargeless and senors usually detect the charge on particles, it is quite difficult for conventional sensors to detect it.

To solve this problem, Parlak decided to build a stretchable, rectangular sensor with a membrane that only binds to cortisol. The patch sucks in sweat from the skin causing the sweat to pool in a reservoir. The membrane then can detect cortisol if cortisol blocks the passage of charged ions like sodium and potassium through the membrane. So it is actually the blocked charges that helps the sensor detect the presence of cortisol.

The device is extremely simple to use, users only need to apply the patch on their skin and then connect it to the device. The device provides the results in few seconds. The research team aspires to make the sensor a part of a fully- integrated system.

As of yet, the sensor works fine, but the research team’s next goal is to make it more accurate and reliable and reusable. It’s not as if the prototype cannot be used multiple times right now, but it is advised that it shouldn’t be after it gets saturated with sweat. Researchers also aim to make the sensor work with saliva, so that users wouldn’t need to sweat to run the test.

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