Microfabrication of high-density microelectrode arrays for in vitro applications

Abstract

Micro Electrode Arrays (MEAs) offer an elegant way to probe the neuronal activity distributed over large populations of neurons either in vitro or in vivo. They also give the possibility to deliver specific electrical stimulations to neuronal networks. This paper will present the fabrication of different kinds of 3D electrode arrays based on silicon micromachining: dense 3D arrays with high aspect ratios (up to 1024 probes with a pitch of 50μm and 80μm of height) and 3D probes enabling recording within the depth of the tissues. Stimulation is also possible with these systems, and we have developed a specific MEA to deliver a focal stimulation in the tissue. The 3D-shaped microelectrodes are necessary to achieve better contacts with the neural tissue, the tip of each needle being the recording site. Indeed, we will detail a new technology based on the Deep Reactive Ion etching technique (DRIE) which offers the possibility to manufacture various shapes of electrodes on silicon. Second, alternative geometries with several contacts on each needle will be described, leading to really 3D probes scanning within the depth of the tissues. Such geometry is based on the combination of DRIE and standard etching techniques. Experiments currently performed have shown that both kind of MEAs present a noise level around 10μV, in the same range as available commercial MEAs. In vitro applications will be presented concerning the study of the whole spinal cord of embryonic mousse and we conceived a new configuration to reach a focal stimulation for in vitro and in vivo applications. © International Federation of Medical and Biological Engineering 2009.