Consider the sad story of sweat: Unless it involves relaxing in a sauna, most of us loathe its feeling—and its smell. Yet sweat provides critical information: People with cystic fibrosis, for instance, have abnormally high chloride levels in their perspiration.

A new wearable sweat sensor developed by Johns Hopkins researchers plays off this fact and aims to monitor and eventually diagnose cystic fibrosis.

To diagnose and monitor cystic fibrosis today, patients must visit clinical labs for a sweat test, a method also invented at Johns Hopkins. The test involves collecting and analyzing perspiration by applying a sweat-stimulating chemical, pilocarpine.

“There have been various upgrades to the technique, but it’s basically remained the same for 57 years,” says pediatrician and medical geneticist Garry Cutting, an adviser to the student design team developing the device.

The tiny prototype relies on a sensor capable of assessing the concentration of chloride ions in a person’s sweat by measuring the potential difference between two small electrodes.

The team is perfecting the sensor to ensure it provides accurate chloride readings done by patients themselves, either through replaceable elements in the device or an entirely replaceable device.

The project emerged after Cutting, biostatistician Scott Zeger and Institute for NanoBioTechnology Director Peter Searson teamed up on a Johns Hopkins Individualized Health Initiative (Hopkins inHealth) program for cystic fibrosis patients.

The sensor could assess other conditions too: Sewn into a garment, the monitor could provide soldiers and athletes with information on their electrolyte balance, indicating what they need to drink to operate at peak performance.  

A patent is pending, while an app and electronics to communicate with smartphones are in development. The team plans to verify the accuracy of the sensor’s measures against that of a sweat test this summer.