Tufts University engineers have developed the world’s first flexible electronic sensing patch that can be stitched into clothing to investigate a person’s sweat for numerous markers.
The electronic sensing patch could be used for diagnosing and tracking chronic and acute health conditions or for monitoring health during workplace or athletic performance. Recently reported in the NPJ Flexible Electronics journal, the device contains electronic components, unique sensing threads, as well as wireless connectivity to acquire, store, and process data in real time.
Temperature, heart rate, walking distance, glucose, and other gross measurements can be tracked by standard consumer health monitors. However, a deeper insight into the stress, health, and performance of a person is needed for collecting medical data and for military and high-performance athletic applications.
Specifically, metabolic markers, such as electrolytes and other kinds of biological molecules, serve as a more direct indicator of human health to precisely evaluate clinical diagnosis, workplace safety, athletic performance, and control chronic health conditions.
Designed by Tufts University engineers, the patch device carries out real-time measurements of crucial biomarkers, such as ammonium and sodium ions (electrolytes), acidity (pH), and lactate (a metabolite), present in sweat.
Also, the device platform is so versatile that it can be integrated into an extensive range of sensors that can track almost each biomarker found in sweat. Such measures can have valuable diagnostic applications.
For instance, sodium present in sweat can denote the electrolyte imbalance and hydration status in a body; concentrations of chloride ions can be used for diagnosing and monitoring cystic fibrosis; lactate levels can indicate muscle fatigue; and the stress hormone cortisol can be used for assessing emotional stress and also immune and metabolic functions.
During physical exertion, athletes could track an extensive range of biomarkers to predict their performance declines or peaks during competition.
Flexible threads coated with conductive inks make it possible to incorporate the sensors into clothing. Different types of coatings tend to modify the functionality of the threads; for instance, coating a thread with an enzymatic sensing material including the lactate oxidase can help detect lactate concentrations.
Similarly, a pH sensing thread is covered with polyaniline that reacts to acidity, etc. The series of thread sensors are incorporated into a patch or clothing and linked to a tiny circuit module as well as microprocessor, with wireless capability to interact with a smartphone.
Sweat is a useful fluid for heath monitoring since it is easily accessible and can be collected non-invasively. The markers we can pick up in sweat also correlate well with blood plasma levels which makes it an excellent surrogate diagnostic fluid.
Trupti Terse-Thakoor, Study First Author and Former Post-Doctoral Scholar, School of Engineering, Tufts University
Scientists tested the device on human subjects and tracked the individuals’ metabolite and electrolyte reaction during the highest physical exertion on stationary bikes. The sensors effectively detected the variation in analyte concentrations as the individuals moved up and down, within intervals of 5 to 30 seconds—adequate for a majority of the real-time tracking requirements.
The human subjects included both men and women who had a range of physical conditioning, from individuals who were physically active on a performance-customized diet to those who were not physically active and had no particular dietary limitations.
While the present study was not intended to establish an association between performance/conditioning and analyte readings, it certainly established that consistent patterns of analyte expression were effectively detected by the sensor. Such analyte expressions could be employed in upcoming studies to detect such correlations.
The sensor patch that we developed is part of a larger strategy to make completely flexible thread-based electronic devices. Flexible devices woven into fabric and acting directly on the skin means that we can track health and performance not only non-invasively, but completely unobtrusively - the wearer may not even feel it or notice it.
Sameer Sonkusale, Study Corresponding Author and Professor of Electrical and Computer Engineering, School of Engineering, Tuft University
The study was funded by grants from the Center for Applied Brain and Cognitive Sciences (CABCS), a U.S. Army Combat Capabilities Development Command, Soldier Center (Cooperative Agreement W911QY-15-2-0001), the Office of Naval Research (N0014-16-1-2550), and the Government of India Department of Science and Technology, and Ministry of Human Resource Development (Scheme for the Promotion of Academic and Research Collaboration).
Terse-Thakoor, T., et al. (2020) Thread-based multiplexed sensor patch for real-time sweat monitoring. npj Flexible Electronics. doi.org/10.1038/s41528-020-00081-w.