Today’s wearables generally depend upon your pulse and heart rate to gauge your fitness and health. A team of scientists from Stanford is taking a closer look at another metric: sweat.
Researchers from the California institution have created a flexible wearable that senses cortisol levels in your sweat. Cortisol, a stress hormone, is often an accurate indicator of athletic performance and potential disease, as it effectively communicates the activity of your adrenal and pituitary glands. Measuring cortisol levels has traditionally required several days of lab tests — but this new wearable reduces the wait time to just a fraction of that.
While sensors generally detect a molecule’s positive or negative charge, cortisol is particularly difficult to track because it is neutral – that is to say, it has no charge. But materials scientist Alberto Salleo created an elegant solution: a stretchy sensor around a membrane that will bind only to cortisol. When this sensor is worn on the skin as a patch, it brings in sweat through small holes at its bottom. Charged particles like sodium and potassium (also found in sweat) will seamlessly pass through the membrane. They’ll be blocked, however, if cortisol is in the way. As such, the sensor can still detect these charged ions, but only if cortisol is present as well.
“We are particularly interested in sweat sensing, because it offers noninvasive and continuous monitoring of various biomarkers for a range of physiological conditions,” said Onur Parlak, a post-doctoral scholar in the Salleo lab and lead author of the paper detailing the team’s findings. “This offers a novel approach for the early detection of various diseases and evaluation of sports performance.”
As it stands, a user only needs to be sweating enough to glisten in order for the patch to work. From there, measuring cortisol levels is just a matter of a few seconds. Of course, the technology has not quite been perfected. Currently, if you’re sweating too profusely, the sensor isn’t quite so effective, which defeats its purpose. Researchers also want to better the general reliability of the data, and are looking into a saliva sensor, so you don’t have to work up a sweat every time you want to track your cortisol levels.
Ultimately, the team hopes to create a device capable of tracking several biomarkers simultaneously, giving folks a clearer and more unique idea of what is happening in their bodies.