A CMOS Integrated Sweat Monitoring System for Medical Applications

Recently, demand for sweat measuring sensors has been increasing, especially for detection of heat stroke, dehydration and pathology of neurological diseases. Currently commercially available sensors are immobile, as they are large and require cables and hoses. Previous studies have presented a design that combines a custom chip analog to digital converter (ADC), discrete capacitive humidity and thermal sensors in a single board. In addition to the ADC, this study integrates a thermal sensor and a time to digital converter (TDC) into a chip. We evaluated the custom chip by comparing the readings of our chip with the market available discrete chip of ADT-7410 inside a environment chamber. Our custom chip size is 2.6 mm2 with a 0.18 $\mu$m CMOS process including TDC and thermal sensor. Our system produces results comparable to those of a commercially available system, while being much smaller.