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Wearable Device Measures Cortisol Levels in Real-Time

Posted July 24, 2018

Current methods of measuring the concentration of cortisol – a hormone commonly known to be related to psychological stress – in a person’s body may take up to several days, which is often too late for the purposes of choosing the right treatment for certain medical conditions or monitoring the performance of athletes.

With the advent of wearable technology, however, a solution was bound to be just around the next bend – this time it comes from a group of materials scientists led by Alberto Salleo at Stanford University.

The group has developed a stretchy patch capable of wicking a bit of sweat from a person’s body surface and taking a direct measurement of how much cortisol is being produced by structures within the adrenal gland.

“We are particularly interested in sweat-sensing, because it offers non-invasive and continuous monitoring of various bio-markers for a range of physiological conditions,” said lead author on the paper Onur Parlak from Stanford.

Applied to sweaty skin, the new device gives a read-out of cortisol levels within seconds, as opposed to several days with current methodologies. Image credit: Minghong via, CC.

Apart from applications in the treatment and management of chronic illnesses, a fully operational version of the device could also be used to reveal the emotional states of young, or even non-verbal, children, who might not be able to communicate it by other means.

In order to overcome the challenge of developing a biosensor to measure cortisol (the challenge being that cortisol molecules have no charge to begin with), Parlak and colleagues built the device around a membrane that binds only to the target compound.

The device works by detecting the amount of charged ions, such as sodium and potassium, accumulated in a specially designed reservoir ­– the more ions, the less cortisol, as the latter prevents the entry of the former through the membrane.

Drawing shows details of the layers contained in the cortisol biosensor developed by the Salleo lab and two close-up images of the holes in the bottom of the sensor that wick in sweat. Image credit: Onur Parlak

“I always get excited about a device, but the sweat collection system that Onur devised is really clever,” Salleo said. “Without any active microfluidics, he’s able to collect enough sweat to do the measurements.”

The device was shown to measure up to the gold standard clinical test both under lab conditions and in the real world – as tested in two volunteers who were asked to jog for 20 minutes and apply the patch to their exposed skin.

In the near future, the team plans to improve the efficiency of the test even further and commence work on a similar device which could perform the measurements based on saliva, rather than sweat, thereby eliminating the need to go for a run every time a cortisol test is in order.


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