Electronic ‘Patch’ Quickly Analyzes Sweat to Monitor Chloride Levels, Overall Health

A research team at Northwestern University has developed a flexible and wearable electronic device, which adheres to the skin, to measure sweat, monitor response to exercise, and detect the presence of certain biomarkers — all of which are relevant for conditions such as cystic fibrosis (CF).

“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,” John A. Rogers, the lead investigator of the project, said in a press release.

Designed for a one-time use of a few hours, patients place the device directly on their skin (the forearm or back). The  microfluidic device, about the size and thickness of a quarter, lets users know in real time if adjustments are needed, like drinking more water or replenishing electrolytes.

It works by absorbing the sweat and analyzing it in four different circular compartments. Reactions with different chemical reagents result in visible color changes in ways that relate to pH level and concentrations of glucose, chloride and lactate.

“We chose these four biomarkers because they provide a characteristic profile that’s relevant for health status determination,” Rogers said. “The device also can determine sweat rate and loss, and it can store samples for subsequent laboratory analysis, if necessary.”

Patients can use a smartphone to trigger an app that captures a photo of the patch, and analyzes the image to yield data on biomarker concentrations.

The research team studied the device’s accuracy and durability, published as the cover story on the November issue of Science Translational Medicine, in the article, “A Soft, Wearable Microfluidic Device for the Capture, Storage, and Colorimetric Sensing of Sweat.”

The study covered tests done on two groups of athletes: one cycling indoors in a fitness center under controlled conditions, and another participating in the El Tour de Tucson, a long-distance cycling competition in dry and complex conditions.

Researchers found that the device successfully captured, stored and analyzed sweat in situ in real time; that it could determine quantitative biomarker levels using colorimetric analysis; and that the device could be read without a power source — a smartphone and dedicated app were all that were necessary to interpret biomarker changes.

Both groups had similar readouts to conventional laboratory analyses of the athletes’ sweat, and found that the two agreed. With the outdoors group, researchers also tested the device’s durability and found it to be resistant, staying on the athletes’ skin and not leaking during vigorous activity.

“We already know how to put electronics on the skin in a natural manner — here our challenge was dealing with fluid flow and the collection, storage and analysis of sweat in a thin, soft and flexible device,” said Yonggang Huang, who collaborated with Rogers in developing the device. “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.”

Below is a video explaining the device.