Wearable Sweat Rate Sensors

Sweat plays a significant role in human homeostasis by regulating the body temperature via evaporative cooling under heat or work stress. Water and electrolytes (mainly sodium and chloride) constitute almost 99% of the sweat composition. Excessive sweat loss disturbs the human homeostasis, impairs circulation, and impedes heat dissipation. Some of the limitations of the conventional sweat loss measurement techniques lie in their wearability, sweat sampling, analyte contamination from skin, and evaporation. To overcome these limitations, we have developed a wearable sensor for continuous sweat rate measurement in wearable form factors. The wearable sensor consists of low-cost printed interdigitated electrodes for impedance sensing, a serpentine shaped paper-based microfluidic channel, and a polyurethane encapsulation layer. In this report, we present the benchtop characterization of the proposed sensor’s capability to track the sweat rate. The microfluidics can hold sweat volumes up to 82 µL and enable the detection of sweat rates on various locations of the body for extended periods.