Researchers, including one of an Indian-origin, have developed wearable skin sensors that use sweat to provide real-time updates on health problems such as dehydration or fatigue. They used the sensors to monitor the sweat rate, electrolytes and metabolites in sweat, from volunteers who were exercising and others who were experiencing chemically-induced perspiration.
"The goal of the project is not just to make the sensors but to study what sweat tells us. For that we need sensors that are reliable, reproducible and that we can fabricate to scale so that we can put multiple sensors in different spots of the body and put them on many subjects," said Ali Javey, Professor at the University of California.
The new sensor design can be rapidly manufactured using a "roll-to-roll" processing technique that essentially prints the sensors onto a sheet of plastic like words on a newspaper.
Roll-to-roll processing enables high-volume production of disposable patches at low cost.
The sensors contain a spiralling microscopic tube or microfluidic that wicks sweat from the skin. By tracking how fast the sweat moves through the microfluidic, the sensors can report how much a person is sweating, or their sweat rate.
To better understand what sweat can say about the real-time health of the human body, the researchers first placed the sweat sensors on different spots on volunteers' bodies and measured their sweat rates, and sodium and potassium levels in their sweat while they exercised.
They found that the sweat rate could indicate the body's overall liquid loss during exercise, meaning that tracking sweat rate might be a way to give athletes a heads up when they may be pushing themselves too hard.
They also used the sensors to compare sweat glucose levels and blood glucose levels in healthy and diabetic patients, and found that a single sweat glucose measurement cannot indicate a person's blood glucose level.
"There's been a lot of hope that non-invasive sweat tests could replace blood-based measurements for diagnosing and monitoring diabetes, but we've shown that there isn't a simple, universal correlation between sweat and blood glucose levels," said Indian-origin researcher and study lead author Mallika Bariya.