Cystic fibrosis is a genetic disorder that affects multiple organs like the lungs and pancreas. It is caused by a mutation a gene called CFTR, which results in the production of a dysfunctional CFTR protein. This protein helps balance salt and water within a cell by acting as a channel for chloride. A mutation in the CFTR protein causes dehydration of mucus secretions and an excessive loss of salt in sweat (salty skin). As a result, some people with cystic fibrosis experience mucus clogs in their airways and are susceptible other complications such as respiratory failure, inflammation, and infection.

In the US and some other developed countries, the initial diagnosis for cystic fibrosis involves measuring specific protein levels from dried blood spots or DNA-based mutation testing. However, these tests are invasive and don't always produce accurate results. Cystic fibrosis can be also diagnosed by testing a person's sweat, to measure their chloride levels and determine whether they have the dysfunctional CFTR protein.

But, collecting enough sweat to do the tests can be a problem. To address this, the researchers behind a new study published in Science have developed a gentle “sweat sticker” that can be used to accurately assess chloride levels outside of clinical and hospital settings. It uses microfluidic technology to rapidly collect chloride levels in a person's sweat, and chloride levels can be analyzed from images captured with a smartphone camera to provide a diagnosis. This relatively simple yet elegant system remains to be tested in a large group of people (this study only had 51 participants), but could make diagnosing cystic fibrosis much easier in the future.