A Multiplexed Electrochemical Measurement System for Characterization of Implanted Electrodes

Microelectrode arrays are important tools that enable a wide range of neuroscience experiments, as well as emerging medical applications of neuroprosthetics and neuromodulation. Design-oriented characterization of electrodes provides information that is important for system optimization and for improving longevity in applications. Of specific interest is electrode impedance and noise across frequency, because these aspects have direct implications for neural recording performance. The time required to perform electrochemical measurements is a major limitation, because each electrode must be characterized individually. A solution is to use a single multiplexed circuit to simultaneously measure multiple electrodes. This report describes the design and in vivo test results of an electrochemical potentiostat system that rapidly multiplexes through electrodes, reducing measurement time for impedance spectroscopy by similar to 8x at frequencies relevant to neural signals (<7.5 kHz). The system was used to gather in vivo characterization data from a microwire array implanted in rodent cortex, and the results are compared to a gold standard bench-top instrument.