Multiphysics Modeling of a Wearable Sensor for Sweat Rate Measurements

Innovative wearable devices are allowing the non-invasive and remote collection of physiological signals from the human body. Sweat analysis has gained remarkable interest for the non-invasive determination of electrolytes and metabolites, particularly in athletes. Monitoring of sweat rate is of interest to support measurements concerning sweat composition and to assess the overall water loss due to physical activity. The final aim is to prevent dehydration and keep an optimal balance of electrolytes, which is important for the safety of athletes and to obtain the best possible performances. We speculate that these devices can also be useful for the protection of workers performing heavy physical tasks. The evaporation of sweat from the skin surface, which is essential for thermal regulation in humans, is largely influenced by ambient factors. Depending on the measurement approach, ambient temperature and humidity as well as air flow do not only affect evaporation but also the measurement of sweat rate. This paper presents a multiphysics model describing the effect of air speed and ambient humidity on an open chamber based sweat rate sensor. Results of simulations will allow to optimize the design of the device so that interferences from ambient conditions are minimized.