Engineers have created a flexible electronic sensing patch that can be sewn into clothing to analyze sweat for multiple markers. The patch could be used to diagnose and monitor acute and chronic health conditions or to monitor health during athletic or workplace performance. The device consists of special sensing threads, flexible electronic components, and wireless connectivity for real-time data acquisition, storage, and processing.
Typical consumer health monitors can track heart rate, temperature, glucose, walking distance, and other gross measurements; however, a more detailed understanding of the health, stress, and performance of an individual is required for medical data collection or high-performance athletic or military applications. In particular, metabolic markers, such as electrolytes and other biological molecules, provide a more direct indicator of human health for accurate assessment of athletic performance, workplace safety, clinical diagnosis, and managing chronic health conditions.
The patch device performs real-time measurements of important biomarkers present in sweat including sodium and ammonium ions (electrolytes), lactate (a metabolite), and acidity (pH). The device platform can also incorporate a wide range of sensors capable of tracking nearly every marker present in sweat. The measurements taken can have useful diagnostic applications: sodium from sweat can indicate the hydration status and electrolyte imbalance in a body; lactate concentration can be an indicator of muscle fatigue; chloride ion levels can be used to diagnosis and monitor cystic fibrosis; and cortisol, a stress hormone, can be used to assess emotional stress as well as metabolic and immune functions. Athletes could monitor a wide range of markers during physical exertion to aid in predicting performance peaks or declines during competition.
The ability to integrate the sensors into clothing is made possible by flexible threads coated with conductive inks. Different coatings alter the functionality of the threads; for example, lactate can be detected by coating a thread with an enzymatic sensing material incorporating the enzyme lactate oxidase. A pH sensing thread is coated with polyaniline that responds to acidity, and so on. The array of thread sensors is integrated into clothing or a patch and connected to a miniature circuit module and microprocessor, with wireless capability to communicate with a smartphone.
Researchers tested the device on human subjects, monitoring their electrolyte and metabolite response during a maximum exertion exercise on stationary bikes. The sensors were able to detect variation in analyte levels as they moved up and down, within 5 to 30 second intervals — sufficient for most real-time tracking needs. The study established that the sensor was able to detect consistent patterns of analyte expression that could be used for future studies identifying these correlations.