Wearable Humidity Sensor for Continuous Sweat Rate Monitoring

The rapid advancements in wearable technologies are allowing for personal and tailored monitoring systems for core bodily metrics. Modern smartwatches accurately and frequently stream physical signals such as heart rate and respiratory rate. However, smartwatches have yet to track a multitude of physiological parameters, including sweat rate. This work presents a new wearable device that tracks sweat rate, the body's most important thermoregulatory function. The device is tape-free and utilizes an off-the-shelf humidity sensor, with the potential to be integrated with existing smartwatch bands. It features a 3D-printed chamber with a humidity sensor and microheater, and it interfaces the skin with a malleable and concave sweat collector. Through various experiments and trials, the authors seek to understand the relationship between sweat-induced humidity within the chamber and the amount of sweat secreted when worn. Compared to existing sweat rate sensing devices, this hygrometer-based device can be worn for extensive periods of time without overfilling. The device's reusability and compactness make it a good candidate for use alongside modern, microfluidic-based sweat rate devices.