Development of wearable thermal MEMS sensor for sweat-rate measurement

Sweat monitoring is gaining increasing attention as a key component of next-generation health technologies. In this study, we developed a compact and flexible wearable sensor based on microelectromechanical systems (MEMS) technology for real-time sweat rate measurement. The sensor detect thermal dissipation of a heat source due to sweat flow within a microchannel, allowing for non-invasive and continuous monitoring. It consists of a microheater and two temperature sensors placed symmetrically upstream and downstream along the microchannel wall. When sweat enters the channel, the convective flow causes a temperature difference between the two sensors, which varies according to the sweat rate. Numerical simulations using finite element analysis were conducted to optimize the sensor geometry, particularly the spacing between the heater and the temperature sensors. The device was fabricated by patterning Cr-Au electrodes onto a flexible polyimide substrate and forming a PDMS microchannel over the sensing area. During exercise experiments, the device was attached to the upper arm of a participant, and the sensor output was recorded wirelessly using a compact data acquisition system. The results showed a clear increase in sweat rate during exercise and a gradual decay during the post-exercise recovery phase. These results demonstrate that the developed device can reliably capture temporal changes in sweat rate, making it a promising candidate for wearable applications in personalized health monitoring and fitness tracking.