Wearable sweat sensors can detect what is in your blood


Needles could be a thing of the past with the development of new sweat sensors that can tell what is in our blood.

Medical technology has been making huge developments in recent years. One recent medical technological development comes from a team of scientists at the University of California, Berkeley. The team is developing wearable skin sensors in the hope that one day, monitoring perspiration could bypass the need for more invasive procedures like blood draws, and provide real-time updates on health problems such as dehydration or fatigue.

The team designed new sweat sensors that 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.

They used the sensors to monitor the sweat rate and the electrolytes and metabolites in sweat from volunteers who were exercising, as well as others who were experiencing chemically induced perspiration.

The secret is in the sweat

The sweat sensors developed by the team 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. The microfluidics are also outfitted with chemical sensors that can detect concentrations of electrolytes like potassium and sodium, and metabolites like glucose.

Professor of Electrical Engineering and Computer Science and UC Berkeley and senior author on the paper, Ali Javey, said: “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”.

During the study the team found that local sweat rate could indicate an individual’s body’s overall liquid loss during exercise, meaning that tracking the sweat rate might be a way to indicate to athletes when they may be pushing themselves too hard.

Developing the sweat sensors

Working alongside researchers at VTT Technical Research Centre, Finland, the team found a quick way of manufacturing the sweat sensor patches in a roll-to-roll process technique similar to screen printing.

Jussi Hiltunen of VTT said: “Roll-to-roll processing enables high-volume production of disposable patches at low cost. Academic groups gain significant benefit from roll-to-roll technology when the number of test devices is not limiting the research. Additionally, up-scaled fabrication demonstrates the potential to apply the sweat-sensing concept in practical applications.

“Traditionally what people have done is collect sweat from the body for a certain amount of time and then analyse it. You couldn’t really see the dynamic changes very well with good resolution. Using these wearable devices, we can now continuously collect data from different parts of the body, for example to understand how the local sweat loss can estimate whole-body fluid loss.”

No correlation between sweat and blood glucose

The sweat sensors were also used to compare sweat glucose levels and blood glucose levels in healthy and diabetic patients. Doing this the team found that a single sweat glucose measurement cannot necessarily indicate a person’s blood glucose level.

Mallika Bariya, co-author author on the paper said: “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, so that going forward we focus on investigating individualised or multi-parameter correlations.”



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