An on-skin platform for wireless monitoring of flow rate, cumulative loss and temperature of sweat in real time

Monitoring the flow rate, cumulative loss and temperature of sweat can provide valuable physiological insights for the diagnosis of thermoregulatory disorders and illnesses related to heat stress. However, obtaining accurate, continuous estimates of these parameters with high temporal resolution remains challenging. Here, we report a platform that can wirelessly measure sweat rate, sweat loss and skin temperature in real time. The approach combines a short, straight fluid passage to capture sweat as it emerges from the skin with a flow sensor that is based on a thermal actuator and precision thermistors, and that is physically isolated from, but thermally coupled to, the sweat. The platform transfers data autonomously using a Bluetooth Low Energy system on a chip. Our approach can also be integrated with advanced microfluidic systems and colorimetric chemical reagents for the measurement of pH and the concentration of chloride, creatinine and glucose in sweat. A wearable platform, which uses a thermal sensing module isolated from biofluids and a Bluetooth Low Energy system on a chip for wireless data transfer, can be used to continuously monitor sweat.