Portable sensors detect the contents of your sweat

Needle bites not your thing? A team of scientists from the University of California, Berkeley, are developing portable skin sensors that can detect what's in your sweat.

They hope that someday, sweat monitoring could avoid resorting to more invasive procedures such as blood sampling and providing real-time updates on health issues such as dehydration or fatigue.

In an article published today in Progress of science, the team describes a new sensor design that can be quickly fabricated using a "roll-to-roll" processing technique that essentially consists of printing the sensors on a plastic sheet, using the words newspaper.

They used sensors to monitor the transpiration rate, as well as the electrolytes and metabolites present in sweat, from volunteers who were exercising and from people suffering from chemical-induced sweating.

"The goal of the project is not just to make sensors, but to start doing many studies on the subject and to see what sweat tells us – I always say" decode " the composition of sweat, "said Ali Javey, professor of electrical engineering and computer science at UC Berkeley and senior author on the paper.

"For that, we need reliable, reproducible sensors, and that we can scale up so we can place multiple sensors at different places on the body and put them on many subjects," said Javey, also university researcher. at the Lawrence Berkeley National Laboratory.

The new sensors contain a microscopic spiral tube, or microfluidic tube, that wicks sweat away from the skin. By detecting the rate of perspiration through microfluidics, sensors can indicate a person's level of perspiration or its transpiration rate.

Microfluidics are also equipped with chemical sensors capable of detecting electrolyte concentrations such as potassium and sodium and metabolites such as glucose.

Javey and his team collaborated with researchers at the VTT Technical Research Center in Finland to develop a way to quickly make sensor patches using roller-like processing similar to screen printing.

"Roller-to-roll processing enables the production of large volumes of low-cost disposable patches," said Jussi Hiltunen of ATV. "Academic groups are reaping considerable benefits from roll-to-roll technology when the number of test devices does not limit research, and large-scale manufacturing demonstrates the potential for applying the concept of sweat detection." in practical applications. "

To better understand what sweat can say about the real-time health of the human body, researchers first placed sweat sensors at various locations in the body of volunteers, including the forehead, the front -arms, armpits and upper back, and measured their transpiration rate. Sodium and potassium levels in their sweat while they were riding on an exercise bike.

They found that the local sweat rate could indicate the overall body fluid loss during exercise, which means that tracking the sweat rate could be a way to give athletes a head whip when They may push themselves too hard.

"Traditionally, people recovered sweat from the body for a while and then analyzed it," said Hnin Yin Yin Nyein, a graduate student in materials science and engineering from UC Berkeley and one of the lead authors on paper. "So you could not really see the dynamic changes with good resolution, and with these portable devices we can now collect data from different parts of the body continuously, for example, to understand how local sweat loss can estimate loss of fluid throughout the body. "

They also used the sensors to compare sweat glucose levels and blood sugar levels in healthy and diabetic patients, finding that a single sweat glucose measurement could not necessarily indicate the level of glucose blood of a person.

"There was much hope that noninvasive sweat tests could replace blood-based measures for the diagnosis and monitoring of diabetes, but we showed that there was no simple and universal correlation between sweat and blood sugar levels, "said Mallika. Bariya, a graduate student in materials science and engineering at UC Berkeley and the other senior author of the journal. "It's important for the community to know, so that in the future we can focus on looking for individualized or multi-parameter correlations."