Portable active sensors for human sweat rate monitoring

A portable active sweat rate sensor has been developed by integrating a thermo-pneumatic actuator with a humidity measuring chamber, making it possible to switch the skin contact of the humidity chamber for long-term continuous human sweat rate measurement. Previous active sweat rate sensor uses an external pump for measuring the humidity difference in the actively ventilated chamber; thus resulting in the problem of the bulky size with the lack of portability. The portable passive sweat rate sensor uses a humidity chamber for measuring the rate of humidity change in the chamber closed by skin. The passive closed chamber sensor, however, needs a manual ventilation of the humidity chamber after each trial measurement. In this study, we present a portable active sweat rate sensor with an integrated thermo-pneumatic actuator; thus making it possible to switch the skin contact of the humidity chamber for continuous sweat rate measurement. The active sweat rate sensor, fabricated in 41 ± 0.5 mm, 38 ± 0.5 mm, and 25 ± 0.5 mm, respectively, is capable to measure the human sweat rate continuously with the sensitivity of 0.093 (pF/sec)/(g/m2h) and the linearity of 99.2 % in the sweat rate range of 3.7~62.9 g/m2h. The present active sweat rate sensor has demonstrated its potential for human sweat rate monitoring applications, such as human thermal status monitoring jackets and air-conditioning systems based on human sweat.