System Integration for Implementation of 3D Neural Probe

Abstract

Microelectrode arrays (MEAs) are devices that provide an interface to neurons via electrodes with feature sizes comparable to individual cells. Through the use of MEAs, it is possible to record or stimulate electrical impulses in neurons, providing a window for examining spatial and temporal activity patterns. Most traditional in vitro MEAs are limited to detecting activity in a 2D plane. However, a large body of research indicates that 2D cultures of neurons do not behave in the same way as neurons in their natural environment, which differ characteristics such as connection structure, spontaneous firing rates, and signal propagation patterns. Additionally, many MEAs are made with either glass or silicon substrates, which are orders of magnitude stiffer than neural tissue. Research has also demonstrated that this mismatch in stiffness has negative consequences on neuron health, resulting in physical changes in cell mobility and structure.

We have designed a novel MEA using a flexible polyimide substrate and Parylene C encapsulation, in order to better match the natural environment of neurons. Additionally, we have developed a system for the stacking of multiple MEA layers, which will allow the recording of neuron activity in a three-dimensional culture. This system consists of a mechanical support structure, electrical readout PCBs, and a novel culturing chamber composed of layers of MEAs. We have validated the functionality of this system, by successfully recording an action potential generated by neurons growing on a flexible MEA. This report describes the features and tradeoffs surrounding the mechanical and electrical readout systems and the experiments informing the culture well design, as well as the process of integrating the system with flexible MEAs and live neurons.