It's important for people with conditions such as depression and anxiety to know when they're becoming stressed, so they can initiate coping strategies. An experimental new smartwatch could someday warn them, by detecting a stress hormone in their sweat.
When someone becomes stressed, their body produces a hormone known as cortisol – the greater the level of stress, the higher the concentration of cortisol in their bloodstream. And while those concentrations can be measured by analyzing blood samples, doing so obviously isn't an effective way of continuously monitoring stress in real time.
Fortunately, cortisol concentrations in the sweat correspond to those in the bloodstream. That's where the prototype smartwatch comes in – it's currently being developed at UCLA, by teams led by Prof. Anne Andrews and Assoc. Prof. Sam Emaminejad.
On the underside of the device is a thin adhesive film, which utilizes microfluidic channels to draw in tiny amounts of sweat from the wearer's skin. That sweat is carried through to a sensor that contains engineered strands of DNA, called aptamers.
Each cortisol molecule in the sweat attaches itself to an aptamer, "like a key fits a lock." The aptamer changes shape as a result, altering the electrical fields on the surface of an adjacent transistor. A microprocessor analyzes the fluctuations of those fields, using them to determine the wearer's current cortisol levels. Those levels are displayed on an LCD screen on the top surface of the watch.
Because every person produces different amounts of cortisol, the watch would initially have to be calibrated to each user, establishing a baseline for their default cortisol levels. Once that baseline was set, the device could warn them when they were becoming dangerously stressed. It could additionally track their cortisol levels over time, to see when and how often they were experiencing elevated stress.
"I anticipate that the ability to monitor variations in cortisol closely across time will be very instructive for people with psychiatric disorders," said Andrews. "They may be able to see something coming or monitor changes in their own personal patterns."
A paper on the study – which is not related to a somewhat similar project at Switzerland's EPFL research institute – was recently published in the journal Science Advances.
Source: UCLA