Stanford wearable gauges stress through sweat

A wearable device developed at Stanford University can detect stress levels by measuring the amount of cortisol in users’ sweat.

Cortisol is a hormone that spikes up and down throughout the day, often in relation to stress. According to the Stanford team, existing methods for measuring the hormone can take several days. This lag makes it difficult to accurately inform medical treatments, despite the fact cortisol levels can be an indicator of adrenal and pituitary gland function.

The prototype wearable, produced out of the lab of materials scientist Alberto Salleo, is a patch that wicks sweat from the skin. Post-doctoral scholar Onur Parlak built a stretchy, rectangular sensor around a membrane that specifically binds only to cortisol. Attached to the skin, it sucks in sweat passively through holes in the bottom of the patch. The sweat collects in a reservoir, which is topped by the cortisol-sensitive membrane. Charged ions like sodium or potassium, also found in sweat, pass through the membrane unless they are blocked by cortisol. It is those charged ions that the sensor detects, as cortisol itself has no charge, presenting a unique challenge.