Wearable sweat sensors

In a new study, researchers from the Indian Institute of Technology Bombay (IIT Bombay) and Tufts University, United States, have developed a novel sensor to detect metabolite levels from sweat. These sensors can be mounted on adhesive bandages and embedded on garments.  The study was published in NPJ Flexible Electronics. “There is a lot of interest in sweat monitoring as it provides a larger window into your health, more than any smartwatch,” says Prof Sameer Sonkusale. He is a Professor at Tufts University and a senior researcher in this study. “Looking for other metabolites in sweat will expand opportunities in medical diagnostics as well,” he adds.  

The researchers developed three types of sensors using carbon-coated polyester threads for sensing electrolytes like sodium and ammonium ions, carbon-coated stainless steel threads to test the pH (acidity) and polyester threads coated with an enzyme that oxidises and senses lactate. The sensors were connected to electronic circuit boards that wirelessly relayed the gathered information to computer programs that calculated the concentrations of different metabolites. “As soon as the sensor sees a difference in ion concentration, the data is transmitted wirelessly almost instantaneously and displayed on the computer (or phone) screen. I would say it takes around a second for this transmission,” says Prof Sonkusale. The sensor threads for sodium ions, ammonium ions, and pH were integrated on one adhesive bandage. The lactate sensors were placed on a separate bandage since their information is processed using a different measuring device. The change in ionic levels is measured through a potentiometer that registers changes in voltage while the lactate concentration is measured in the form of current via an ammeter. The sensor patch was covered with gauze, which provided an absorbent surface to collect the sweat.  

The complete sensor bandages were placed on the arms, forehead and lower back of the study participants while performing mild exercises. They took 10–20 minutes to break into a sweat, which was absorbed by the gauze. The sensor detected different ions and allowed the researchers to gather data depicting real-time changes in ionic levels. This data can be used to analyse the fitness of the participants. “Achieving a sensor that seamlessly integrates with the body without any discomfort and inconvenience to the user is quite a challenge since every sensor and electronics platform adds to bulk and rigidity making it incompatible,” says Prof Sonkusale. “Our textile threads serve as ideal substrates since it can be functionalized to monitor different biomarkers in sweat, and can be integrated on any garment or even as a standalone patch. The latter was what we did,” he concludes. 

(Source: IIT Mumbai news release)