Impedance and Noise Characterizations of Utah and Microwire Electrode Arrays

This paper presents an in-depth noise and impedance characterization of two of the most widely used microelectrode arrays (the Utah Electrode Array (UEA) and the Tucker-Davis Technologies (TDT) Microwire Array) and provides quantitative analysis of how properties change when implanted in rodent cortex. Custom low-noise circuits and de-embedding methods were designed to acquire nV / √Hz noise power spectral densities from high-impedance electrodes. A total of 80 electrodes were implanted across five rats and measured under deep anesthesia, demonstrating a 1.5× to 3× increase in noise and 2.25× to 9× in impedance compared to in vitro measurements. Low-frequency biological noise was also observed and studied through postmortem measurements. These results are informative for designing neural interfacing systems for both neuroscience and medical applications.