Wearable multiplexed biosensor system toward continuous monitoring of metabolites

Comprehensive metabolic panels are the most reliable and common methods for monitoring general physiology in clinical healthcare. Translation of this clinical practice to personal health and wellness tracking requires reliable, non-invasive, miniaturized, ambulatory, and inexpensive systems for continuous measurement of biochemical analytes. We report the design and characterization of a wearable system with a flexible sensor array for non-invasive and continuous monitoring of human biochemistry. The system includes signal conditioning, processing, and transmission parts for continuous measurement of glucose, lactate, pH, and temperature. The system can operate three discrete electrochemical cells. The system draws 15 mA under continuous operation when powered by a 3.7 V 150 mAh battery. The analog front-end of the electrochemical cells has four potentiostats and three multiplexers for multiplexed and parallel readout from twelve working electrodes. Utilization of redundant working electrodes improves the measurement accuracy of sensors by averaging chronoamperometric responses across the array. The operation of the system is demonstrated in vitro by simultaneous measurement of glucose and lactate, pH, and skin temperature. In benchtop measurements, the sensors are shown to have sensitivities of 26.31 μA mM^-1·cm^-2 for glucose, 1.49 μA mM^-1·cm^-2 for lactate, 54 mV·pH^-1 for pH, and 0.002 °C^-1 for temperature. With the custom wearable system, these values were 0.84 ± 0.03 mV μM^-1·cm^-2 or glucose, 31.87 ± 9.03 mV mM^-1·cm^-2 for lactate, 57.18 ± 1.43 mV·pH^-1 for pH, and 63.4 μV·°C^-1 for temperature. This miniaturized wearable system enables future evaluation of temporal changes of the sweat biomarkers.