sweat sensor

Wristband diagnoses cystic fibrosis through sweat, transmits results to the cloud

Image credit: Sam Emaminejad- Stanford Medicine

A wearable wristband sensor that can diagnose cystic fibrosis by analysing sweat could transform diagnostics and drug evaluation for the disease, according to its creators.

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 professor Carlos Milla described the device as “a huge step forward”.

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.

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 specialised centre 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 said. Children have to sit still for 30 minutes while an instrument attached to their skin collects sweat. Even then, the test isn’t over. Families wait while a lab measures the chloride ions in the sweat to determine if the child has the disease.

Milla said this cumbersome method hasn’t changed in 70 years. 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 analyse the results.

The test happens all at once and in real time, Milla said, making it much easier for families to have kids evaluated. Additionally, people living in under-served communities or in out-of-the-way villages in developing countries, where conventional testing is unavailable, could benefit from a portable, self-contained sweat sensor, he said.

The wearable device is robust and can be run with a smartphone, which can send measurements to the cloud and receive a result straight back after review at a specialised centre. Cystic fibrosis 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 said.

The sensor is not only for diagnosis and monitoring: it could also be used to help with drug development and drug personalisation.

Cystic fibrosis [CF] 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. “CF drugs work on only a fraction of patients,” said Emaminejad, who is now an assistant professor of electrical engineering at UCLA. “Just imagine if you use the wearable sweat sensor with people in clinical drug investigations; we could get a much better insight into how their chloride ions go up and down in response to a drug.”

For this study, the research team also measured glucose levels in sweat, which correspond to blood glucose levels, making the device potentially useful for monitoring pre-diabetes and diabetes. 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,” Davis said.

The team is now working on large-scale clinical studies to look for correlations between sweat-sensor readings and health. “In the longer term, we want to integrate it into a smartwatch format for broad population monitoring,” Emaminejad said.

Last year, a team developed a flexible alcohol-detecting wearable sensor that accurately measures blood alcohol levels from sweat and transmits the data wirelessly to a smartphone app to let users know when they are over the limit. 

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