Wearable sweat monitoring patch allows athletes to track electrolyte loss on the fly

Scientists have developed a small device – just a couple of centimetres across – which when worn on the skin measures sweat levels. Knowridge reports that the soft and stretchable device can detect key markers such as glucose and pH, presenting the information to the user via a smartphone app.

Reporting results of a recent trial of the device in the journal Science Translational Medicine, the researchers said one of the attractions was that it allows people to monitor their health on the spot without the need for blood sampling.

"Sweat is a rich, chemical broth containing a number of important chemical compounds with physiological health information," said John Rogers, a professor at Northwestern University in the United States who led development.

> Is this edible water blob the future of cycling water bottles?

Sweat winds through the device’s tiny microscopic channels into four compartments and there reacts with chemical reagents to produce colour-based readings relating to pH and to concentrations of glucose, chloride and lactate. The patch’s integrated electronics allow it to connect wirelessly with a smartphone where the data is analysed. It is designed to be used only once, for a few hours at a time.

The trial saw sweat monitoring patches placed on the arms and backs of two groups of cyclists. The first group cycled indoors under controlled conditions. The second raced the 104km El Tour de Tucson in arid conditions.

The indoor trial indicated that the device’s measurements and readings were as good as conventional laboratory analyses of the same sweat. When used outdoors, riders reported no discomfort as a result of wearing the device, which stayed in place, did not leak, and was said to have provided good quality readings.

Rogers said that as well as monitoring electrolyte balance, the device can also detect a biomarker for cystic fibrosis. He suggested it could potentially be adapted to help diagnose disease or monitor the health of people with chronic illnesses.