Simultaneous impedance measurements of the Utah electrodes array : A finite element method analysis

High-count micro-electrode arrays for the recording or stimulation of the nervous system have the potential to restore function lost to disease or injury. The tracking of the electrode characteristics and changes over time becomes crucial for reliability evaluation and human implementation. Current approaches to impedance measurement are manual and often restricted to a single frequency (1 kHz). Channels are evaluated serially. When 100 or more channels are present, the process can become time-consuming. In this paper, we use finite element method (FEM) modeling for studying the impact of simultaneous impedance measurement of 100 electrodes of a Utah Electrode Array (UEA). We simulate potentiostatic impedance spectroscopy of a UEA implanted in the brain. The simulations have been performed using a 25 mV excitation voltage, applied to a common reference, at frequency range from 1 Hz to 10 MHz. Each individual electrode channel is held at ground potential and the current through each channel is measured to determine impedance. Higher impedance has been found when measuring the electrodes simultaneously versus measurement of a single electrode, due to crowding of electric field lines near the electrode tissue interface.