The combination of sweat and mobile health can be used in tandem to better predict and track chronic disease, says Stanford University School of Medical School.

Stanford has developed a wristband-type wearable sweat sensor Stanford says could transform diagnostics and drug evaluation for cystic fibrosis, diabetes and other diseases.

The sensor collects sweat, measures its molecular constituents and then electronically transmits the results for analysis and diagnostics, according to a study led by researchers at the Stanford University School of Medicine, in collaboration with the University of California-Berkeley. Unlike old-fashioned sweat collectors, the new device does not require patients to sit still for a long time while sweat accumulates in the collectors, Stanford says.

“This is a huge step forward,” says Dr. Carlos Milla, associate professor of pediatrics at Stanford.

The two-part system of flexible sensors and microprocessors sticks to the skin, stimulates the sweat glands and then detects the presence of different molecules and ions based on their electrical signals.

The more chloride in the sweat, for example, the more electrical voltage is generated at the sensor’s surface. The team used the wearable sweat sensor in separate studies to detect chloride ion levels — high levels are an indicator of cystic fibrosis — and to compare levels of glucose in sweat to that in blood. High blood glucose levels can indicate diabetes, Stanford says.

Conventional methods for diagnosing cystic fibrosis—a genetic disease that causes mucus to build up in the lungs, pancreas and other organs — require that patients visit a specialized center and sit still while electrodes stimulate sweat glands in their skin to provide sweat for the test. The electrodes can be annoying, especially for kids, in whom cystic fibrosis is most often diagnosed, Milla says. Then, children have to sit still for 30 minutes while an instrument attached to their skin collects sweat. Even then, the test isn’t over, he says. Families wait while a lab measures the chloride ions in the sweat to determine if the child has cystic fibrosis.

This cumbersome method hasn’t changed in 70 years, Milla says. By comparison, the wearable sweat sensor stimulates the skin to produce minute amounts of sweat, quickly evaluates the contents and beams the data by way of a cellphone to a server that can analyze the results. The test happens all at once and in real time, Milla says, making it much easier for families to have kids evaluated.

The wearable device is robust and can be run with a smartphone, which can send measurements to a cloud and receive a result right back after review at a specialized center. CF diagnosis, as well as other kinds of diagnoses, could be done without needing a staff of skilled clinicians on duty and a well-equipped lab. “You can get a reading anywhere in the world,” Milla says.

The sensor is not only for diagnosis and monitoring. It could also be used to help with drug development and drug personalization. Cystic fibrosis is caused by any of hundreds of different mutations in the cystic fibrosis gene, so it’s possible to use the sensor to determine which drugs work best for which mutations.

For this study, researchers also measured glucose levels in sweat, which correspond to blood glucose levels, making the device potentially useful for monitoring pre-diabetes and diabetes. But the technology can also be used to measure other molecular constituents of sweat, such as sodium and potassium ions and lactate. The platform can be used to measure virtually anything found in sweat.

“Sweat is hugely amenable to wearable applications and a rich source of information,” Stanford says.

A wearable sweat sensor allows for frequent monitoring to see how patients respond to a treatment or if they’re complying with treatment, Milla says. “It’s a little like the old days when people with diabetes had to come into a clinic to get their glucose monitored. The real revolution came when people started to do their own finger stick, and nowadays you can even do it with continuous monitors.”

Davis sees two major challenges with a wearable sweat sensor. One is reproducibility—that is, how consistent measures are in the same person from day to day or hour to hour. “Under the same biological conditions even with the same person, do you get the same number?”

The second is mapping the molecular constituents of sweat. In short, what is in sweat that could reasonably be monitored to provide useful information about the body? “We’re kind of limited with what we can actually measure so far. We can measure chloride, for example, so we’re trying to figure out what we can use that for,” Davis says.