A scientist from Stanford University has developed a patch that can measure cortisol levels in sweat in almost no time at all.

Cortisol, a hormone that naturally increases and decreases throughout the day, often spiking in response to stress, can be an indicator of certain medical conditions. Currently, measuring cortisol levels often takes several days, making it nearly impossible to treat certain medical conditions in a timely manner.

"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. "This offers a novel approach for the early detection of various diseases and evaluation of sports performance."

The wearable sensor surrounded by a membrane that binds to cortisol only, is stretchy and sticks to the skin, collecting sweat through holes in the patch. The sweat pools in a type of reservoir that is covered by a cortisol sensitive membrane. Passing through the membrane are charged ions such as sodium and potassium (also found in sweat), unless blocked by cortisol. These charged ions blocked from passing through the membrane are what is detected by the sensor.

"I always get excited about a device, but the sweat collection system that Onur devised is really clever," said materials scientist Alberto Salleo at Stanford University. "Without any active microfluidics, he's able to collect enough sweat to do the measurements."

Still in the testing stages, the patch only requires sweat to determine cortisol levels and not even that much (just enough to glisten). Once the patch is applied and then connected to a device for analysis, cortisol measurements are available within seconds.

The study is published in the journal Science Advances.