Characterization of silicon microelectrodes from the eu vsamuel project

The principle goal of the European Commission sponsored VSAMUEL project is to develop the means to enable neuroscientists and engineers to acquire simultaneous recordings of the activity of hundreds of cells in the central nervous system in the animal model. To attain these goals, VSAMUEL consortium is developing a multi-sited microelectrode array based on batch fabricated Siliconon-Insulator wafers, connected to the outside world via flexible interconnects. As a measure to control the quality of VSAMUEL probes, several characterizations are under evaluation. They must first be simple enough to be able to be performed at the manufacturing site, and perhaps by the end user, yet, they must be comprehensive enough to detect flaws of the electrode or predict the performance of the electrode during use. We have focused on three methods of probe characterization: visual, electrical and mechanical. The present paper focuses on the latter two characterizations. “Visual" characterizations involve the use of electron- and optical microscopes and are primarily used to identify structural faults from the manufacturing process and will be reported elsewhere. Electrical characterisation was performed using a novel rapid 3-point electrode impedance characterisation system with the probes immersed in normal (0.9%) saline. Mechanical characterisation is made using a recently developed force measurement device to determine insertion mechanics of the probes implantation into nervous tissue. As a first step towards designing these tests, we are running comprehensive characterizations of electrode impedance spectra and destructive mechanical testing to determine the signature characteristics of a normal, functioning probe and its possible failure modes. Once identified, simpler evaluation tests could be designed and implemented for quality control