Developing a thin-film multielectrode array system for neuron sensing in three-dimensions

Abstract

Multielectrode arrays (MEAs) are used \textit{in vitro} and \textit{in vivo} to interface neural tissue with external electronics. Recent advances in MEA design have begun paving the way for the development of brain-computer interfaces, including control of neuro-prosthetic limbs. \textit{In vitro}, MEAs are also used to research neural network communication and growth by facilitating the stimulation and recording of multiple neurons simultaneously. However, many traditional MEA devices only capture neural activity in a two-dimensional plane, preventing an accurate description of the three-dimensional conformations present in living tissue. Many devices are also made from rigid materials that irritate surrounding tissue due to mechanical mismatch. We have designed a new multielectrode array on a flexible polyimide substrate. Using a custom designed readout system, we have characterized the impedance spectra for our fabricated sensors. By fitting an equivalent circuit model to the experimental data, we find that the impedances obtained for the various circuit elements are larger but of the same order of magnitude as those predicted theoretically. Evidence during fabrication steps as well as a larger-than-predicted wire resistance in our sensor suggests that the insulating polyimide layer may have only been partially removed from the desired surface contacts of the sensor. We have also confirmed that surface of the array is amenable to the growth of superior cervical ganglion neurons.