A CMOS ISFET array for wearable thermoelectrically powered perspiration analysis

Recent advances in micro-electronics and electro-chemical sensors has led to an emerging class of next generation wearables, detecting analytes in bio-fluids such as perspiration. Most of these devices utilise Ion Selective Electrodes (ISEs) as a detection method, however Ion Sensitive Field Effect Transistors (ISFETs) provide a solution with better integration and low-power consumption. This work presents a system consisting of an ISFET array designed to read the pH of perspiration as a current, average the signal to reduce noise and modulate the frequency of a transmittable pulse. The input referred noise of the array is shown to be reduced by a factor of 3, compared to a single sensor of the same overall power consumption. The sensing and processing system consumes less than 10μW making it feasible to be supplied by a thermoelectric generator.

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