Move over Fitbit: Sweat-sensing bracelet could be next wearable tech
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The next wearable device isn’t interested in your body’s movements, but rather its molecules.

Scientists have recently developed a set of sensors that sit on your skin, such as in a wristband or headband, and continuously measure levels of chemicals in your sweat, which they say could someday be used for a wide range of health analyses.

This sensor is a new development in the field of “wearables”  technology that you wear on your body, which run the gamut from Fitbits that monitor physical activity to plastic leg braces that allow you to sit down in midair.

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In a new paper, researchers describe a novel sweat monitor embedded on a translucent bracelet. The monitor itself consists of a sensor array and flexible circuit board that measures the concentration of various chemicals in sweat, as well as a Bluetooth transmitter that beams the data to a phone. Human subjects wore it on their wrist or head, and scientists measured data during exercise sessions.

The researchers measured four chemicals  sodium, potassium, glucose, and lactate  with this proof-of-concept device. The paper shows that researchers can detect dehydration in runners based on the concentration of sodium in their sweat. The results are detailed in a Nature paper published Wednesday.

Lead author and Berkeley professor Ali Javey said that sweat contains “a whole library” of chemicals, like electrolytes, proteins, and heavy metals, which could present many opportunities for future studies. He said that his group is studying how a variety of diseases could be detected from sweat.

“I think if you could have a pathology lab on your hand, that would be an amazing breakthrough for humanity as a whole,” Javey said.

This wrist monitor continuously measures chemicals in your sweat.
Wei GaoThis wrist monitor continuously measures chemicals in your sweat.

However that is some way off. Sweat analysis is presently used, for instance, to diagnose cystic fibrosis and to test for use of illicit drugs. But the science of using sweat to more generally track a person’s health is far from fully developed.

In an accompanying commentary, Jason Heikenfeld, chief science officer of Eccrine Systems, which is working to develop similar wearables, described other potential applications. Sweat, he wrote, could help inform drug dosing by measuring how quickly patients metabolize drugs, or could reveal a person’s stress levels by monitoring their cortisol.

The device Javey’s group has developed is innovative, says Vlad Oncescu, a management consultant, who was not involved in this research and has done similar work before at Cornell. But it is “lacking in demonstrating how the device can be used for practical applications.”

Indeed, Javey said, much more research needs to be done on what sweat composition actually tells us about disease.

Even if the technology were to provide useful data, some wonder whether such quantifying technology is the right way to learn about our bodies.

“You might think there’s something really valuable to being able to introspect into whether you’re hungry, or thirsty, or tired,” said Karola Kreitmair, an affiliate of the Stanford Center for Biomedical Ethics. “[This device] takes you out of yourself.”

Nevertheless, interest in these devices is racing ahead, with companies such as Kenzen and Eccrine Systems developing sweat-detecting wearables.

“Could you imagine living without your smartphone and all the information it gives you each day?” Heikenfeld said. The same will eventually be true, he believes, about information about our bodies. “At some point, we’re going to know what’s going on with ourselves more.”

Kreitmair said this might not be a good thing.

“It might be true that we feel like we can’t live without our smartphones,” she said. “Has this really engendered more peace of mind? Has this led to more satisfaction and enjoyment of our lives? I would venture to say, probably not.”

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