Design of a Calorimetric Flow Rate Sensor for On-Body Sweat Monitoring

In order to normalise measured concentrations of biomarkers in sweat, many of which are sweat rate dependent, a multi-modal analysis which measures flow rate alongside biomarker concentration is required. This paper presents an overview of current methods, as well as a detailed design of a calorimetric system to measure the flow rate of sweat, including the fluidic channel, signal conditioning circuits, and power regulation. Through simulation of the full system using LTSpice and SOLIDWORKS FlowSimulation, the final design achieved a minimum resolution of 0.85 pL/min, as well as an average error of 1.87% across the 0.5 to 20 pL/min measurement range.