3 mm Deep microelectrode needle array based on aluminum for neural applications

This paper presents a simple and cost-effective fabrication method of invasive neural microelectrode arrays based on aluminum, which is a viable alternative to other state-of-the-art technologies that rely primarily on silicon. A 10 × 10 array with 3.0 mm deep reaching pillars were fabricated, each having a pyramidal tip profile. Each aluminum pillar is insulated with a biocompatible layer of aluminum oxide. The electrode tip was covered by an iridium oxide thin-film layer via pulsed sputtering, providing a stable and a reversible behavior for recording/stimulation purposes, each with a 145 Ohm impedance in a wide frequency range of interest (10 Hz-100 kHz). Each pillar is electrically individualized from the adjacent ones by an insulating layer of epoxy resin. High-aspect-ratio pillars (20:1) are achieved through a combination of dicing, thin-film deposition, anodizing and wet-etching. The described approach allows an array of deeper penetrating electrodes and a simpler fabrication procedure when compared to previous works.