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Wearable sweat sensors that tell you what's in your blood are now a reality

Thirsty workout in heatwave
(Image credit: Getty)

A new breakthrough in medical technology could see wearable sweat sensors replace drawing blood for a number of a common health measurements one day.

In a research paper published in Science Advances, scientists at the University of California, Berkeley outline how tracking perspiration can offer a non-invasive window into the contents of your blood.

At the heart of the sweat sensors is a microscopic tube called a microfluidic, which tracks a person's sweat rate and comes equipped with chemical sensors to detect electrolytes like potassium and sodium, as well as metabolites like glucose.

Taken together, the researchers say these measurements can offer real-time insights into health issues like fatigue and dehydration.

The team tested their sensors on volunteers sweating due to physical activity, using an exercise bike similar to what you might find in a home gym. They also attained a test sample from participants experiencing 'chemically induced' perspiration.

Fast production key to success

Part of the success of the research is down to the ease with which the new technology can be produced to scale – using a 'roll-to-roll' processing method similar to how words are printed on a newspaper, multiple sensors can be printed onto sheets of plastic.

According to the Ali Javey, Professor of Electrical Engineering and Computer Science at UC Berkeley and one of the senior authors of the study, this means the publication of the research paper is just the beginning for the project.

“The goal of the project is not just to make the sensors but start to do many subject studies and see what sweat tells us – I always say ‘decoding’ sweat composition. 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," he said.

The hope is that the more beads of sweat the scientists are able to analyse, the more useful the wearable sensors will become, with both medical and consumer use cases possible further down the line.

Given that the best fitness trackers now integrate heart rate monitors and DNA testing kits can be used from the comfort of your home, the possibilities for wearable sweat analysis seem immense.

Bittersweet news for diabetics

However, the researchers did highlight one key limitation to their work, stressing that their testing failed to reveal a direct correlation between sweat glucose levels and blood glucose levels.

This means that the wearable sweat sensors, at least in their present form, would be of little use to diabetics hoping for an alternative to the needle pricks necessitated until recently by even the best glucose meters. In 2017 the FDA did approve a bloodless glucometer, but these are currently pricey and still require lancets of blood if readings don't match symptoms. 

"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. This is important for the community to know," said Mallika Bariya, Study Lead Author and Graduate Student in Materials Science and Engineering at UC Berkeley.

As a result, it seems that blood tests are unlikely to be consigned to the annals of medical history any time soon – though wearable sweat sensors may be able to offer an alternative to the needle in certain situations.

The paper was developed in partnership with and co-authored by researchers at the VTT Technical Research Center of Finland.