A team of researchers from Stanford University has developed a wearable patch that can measure a person’s cortisol levels from their sweat. Cortisol is a hormone that increases in response to stress. This important biomarker can measure everything from stress to immune function.
However, current methods for measuring cortisol levels typically takes several days to test. The new patch developed by scientists can assess how much cortisol an individual is producing by wicking up sweat.
The findings of the research, which was led by Alberto Salleo, was published in the journal Science Advances.
“We are particularly interested in sweat sensing, because it offers noninvasive and continuous monitoring of various biomarkers for a range of physiological conditions,” said lead author Onur Parlak, a post-doctoral scholar in the Salleo lab. “This offers a novel approach for the early detection of various diseases and evaluation of sports performance.”
The stretchy patch called MS-OECT, has sensors that can specifically attach to cortisol while allowing other properties to pass through its membrane.
“We introduce the integration of an electrochemical transistor and a tailor-made synthetic and biomimetic polymeric membrane, which acts as a molecular memory layer facilitating the stable and selective molecular recognition of the human stress hormone cortisol,” the authors wrote. “The sensor and a laser-patterned microcapillary channel array are integrated in a wearable sweat diagnostics platform, providing accurate sweat acquisition and precise sample delivery to the sensor interface.”
Biosensors detect a molecule’s positive or negative charge, but cortisol has no charge. To overcome this obstacle, Parlak built his sensor around a membrane that specifically binds only to cortisol. The patch sucks in sweat passively through holes at the bottom. The sweat is then collected in a reservoir which is covered by the cortisol-sensitive membrane. Charged ions such as potassium and sodium passes through the membrane unless they’re barred by the cortisol. The sensor detects these backed up charged ions, and not the cortisol itself. The patch has a waterproof layer on top that protects it from contamination.
“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.”
To measure cortisol level, all you have to do is sweat, apply the patch and connect it to a device for analysis. It will give you results in seconds. The researchers hope that in the future the sensor would become part of a fully integrated system.