A team of scientists is developing wearable skin sensors that can detect what’s in your sweat


Needle pricks not your thing?

A team of scientists at the University of California, Berkeley, is developing wearable skin sensors that can detect what’s in your sweat.

They 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.

In a paper appearing today in Science Advances, the team describes a new sensor design 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, and others who were experiencing chemically induced perspiration.

“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,” said Ali Javey, a professor of electrical engineering and computer science at UC Berkeley and senior author on the paper.

“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 Javey, who also serves as a faculty scientist at Lawrence Berkeley National Laboratory.

Wearable sensors detect what's in your sweat
New wearable sensors developed by scientists at UC Berkeley can provide real-time measurements of sweat rate and electrolytes and metabolites in sweat. The sensors can be rapidly manufactured using a roll-to-roll processing technique that prints the sensors onto a sheet of plastic. Credit: Antti Veijola, VTT Technical Research Center of Finland

The new sensors contain a spiraling 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.

Javey and his team worked with researchers at the VTT Technical Research Center of Finland to develop a way to quickly manufacture the sensor patches in a roll-to-roll processing technique similar to screen printing.

“Roll-to-roll processing enables high-volume production of disposable patches at low cost,” Jussi Hiltunen of VTT said.

“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.”

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 – including the forehead, forearm, underarm and upper back – and measured their sweat rates and the sodium and potassium levels in their sweat while they rode on an exercise bike.

They found that local 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.

“Traditionally what people have done is they would collect sweat from the body for a certain amount of time and then analyze it,” said Hnin Yin Yin Nyein, a graduate student in materials science and engineering at UC Berkeley and one of the lead authors on the paper.

“So 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.”

They also used the sensors to compare sweat glucose levels and blood glucose levels in healthy and diabetic patients, finding that a single sweat glucose measurement cannot necessarily 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 Mallika Bariya, a graduate student in materials science and engineering at UC Berkeley and the other lead author on the paper.

“This is important for the community to know, so that going forward we focus on investigating individualized or multi-parameter correlations.”

Epicore Biosystems has developed a patch to capture and analyse your sweat.

It’a a wearable technology to capture sweat, analyse the unique biomarkers within it and offer custom hydration recommendations based on it.

The goal is to ensure athletes are drinking enough fluids – and the right kinds of fluids – at half-time to maintain peak levels throughout the game.

Epicore has been working with sports drink giant Gatorade to commercialise its technology, and later this month the pair are preparing to officially launch the microfluidic Gx Sweat Patch.

It’s a single-use adhesive product that captures the slick stuff and mixes it with a built-in food dye to offer colour-coded insights based upon the volume of sweat and its biochemical makeup.

How does it work?

How wearable sweat trackers are providing athletes with critical hydration insights

Some quick image processing is done by taking a picture using a companion smartphone app to reveal sweat rate and electrolyte readings. This will show athletes what, and how much, they need to drink to give the body the fluids it needs to replenish in that moment.

“The basis of our work with Gatorade began with the idea that we could build a sports electrolyte and sweat rate monitor with a view to tracking hydration and electrolyte loss for the athlete,” Epicore co-founder and CEO Roozbeh Ghaffari tells us in an interview.

The patch has been developed further and tested at the Gatorade Sports Science Institute in Bradenton, Florida, ahead of distribution to the vast array of teams and professional, college and high school athletes on Gatorade’s roster this year. Consumers will get it in 2020, but there’s no official word on the price yet.

At all levels, the patch will be a single use item that’s thrown away (or hopefully recycled) after use. That means no cleaning, no need to replenish the reactive dye or problems with adhesive for repeat usage. However, in this climate of renewed environmental consciousness, do we really need more items containing single-use plastics from a sports drinks company?

“We spend a lot of time on the use case for this first-gen product and decided single use was the way to go,” Ghaffari says. “These [are] materials that can be dropped in a regular recycling box. We do have the capability to build in Bluetooth and NFC, but that would require a battery. In a lot of cases, the battery is the biggest driver of waste.

“From our standpoint, it’s not meant to be a device that you use every day, the way you would a Fitbit. A pack of 12 may be good enough for a season, to give you a quick snapshot at the end of the exercise, or at half time.”

It doesn’t appear consumers will get the same sports science-based insights as those in the elite sports world, though, and will simply get a hydration recommendation.

For Gatorade (owned by PepsiCo), the motivation here is quite simple. It wants to provide athletes with accurate data advising them to drink more Gatorade – specifically the custom-made Gx concentrated liquid pods tailored specifically to the individual athlete’s needs – in order to replenish hydration and electrolyte levels.

However, the arrangement with Gatorade company covers just one use of Epicore’s overarching technology; commercialisation in the field of sports performance. This gives Epicore great scope to partner with others and pursue other avenues beyond the Gx patch.

More information: H.Y.Y. Nyein el al., “Regional and correlative sweat analysis using high-throughput microfluidic sensing patches toward decoding sweat,” Science Advances (2019). DOI: 10.1126/sciadv.aaw9906 , https://advances.sciencemag.org/content/5/8/eaaw9906

Journal information: Science Advances
Provided by University of California – Berkeley


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