Biomarkers in human sweat could be used to monitor a patient’s health without blood samples if the sweat sample collection and measurement can be controlled. A multi-institution research team led by John Rogers of the McCormick School of Engineering and Northwestern University’s Feinberg School of Medicine has developed a wearable, microfluidic system for sweat analysis in the form of a skin patch.

The challenges of constructing a skin-wearable, electronic sweat patch include making the device flexible and stretchable to move naturally with the skin. Rogers and collaborator Yonggang Huang of the McCormick School of Engineering had previously developed skin-like stretchable electronics, but the sweat patch was their first device to monitor physiological health by analyzing biofluids. About the size and thickness of a quarter, the sweat patch analyzes biomarkers that show the effect of exercise and can alert the subject to drink more water or replenish electrolytes if necessary. The patch  is a one-time device used for just a few hours, placed on the forearm or back. Potential applications go far beyond exercise hydration.

Recent successful testing of two groups to determine biomarker measurement accuracy (compared to traditional sweat collection methods) and device durability demonstrated three breakthroughs: the device can capture, store, and analyze sweat in place in real time; colorimetric analysis of sweat samples accurately determines biomarker levels; and the no battery or external power source is necessary to display results, which can be seen on a smartphone app.

“Sweat is a rich, chemical broth containing a number of important chemical compounds with physiological health information. By expanding our previously developed ‘epidermal’ electronics platform to include a complex network of microfluidic channels and storage reservoirs, we now can perform biochemical analysis of this important biofluid,” Rogers said. Still in development, the sweat patch can detect a biomarker for cystic fibrosis. According to the researchers, with further development it could be used for a wide range of disease diagnosis.

“The sweat analysis platform we developed will allow people to monitor their health on the spot without the need for a blood sampling and with integrated electronics that do not require a battery but still enable wireless connection to a smartphone,” Huang said. A smartphone held close to the patch triggers the associated app to capture a photo of the sweat patch device. The app then uses colorimetric analysis for data on biomarker concentrations.