Electrochemical Impedance Spectroscopy Analog Frontend Optimized for Mobile Biosensing Applications

Electrochemical impedance spectroscopy (EIS) represents a promising and rapidly growing biosensing technique, enabling researchers and clinicians to perform label-free analyte detection; however, the scarcity of small, low-cost, and energy-efficient mobile devices for impedance measurement presents a major obstacle to further utilization of this method. Many EIS analog frontend (AFE) integrated circuits meeting these criteria are not commercially available; equivalent discrete circuits are frequently too expensive, large, or energy-inefficient for broad deployment. We present a discrete EIS-AFE which encodes impedance magnitude and phase as DC potentials; our AFE is optimized to minimize energy expenditure (<21 μJ per point at 10 kHz), size (<91 mm 2 for the detector circuits), computational overhead (requiring only three ADC samples), and design complexity to target edge sensing applications (such as single-frequency EIS). We characterize the performance of the custom AFE, perform a comparative power analysis, and demonstrate successful EIS sensing using a series of dummy cells and a synthetic tissue analog saturated with artificial sweat. Our AFE enables accurate acquisition of impedance data with considerable power and cost savings relative to similar devices, while enabling modular expansion of the system to facilitate EIS sensing in a variety of mobile sensing applications.