High-density 3D pyramid-shaped microelectrode arrays for brain-machine interface applications

This paper presents a novel, 3D, pyramid-shaped, penetrating, silicon-based microelectrode array (MEA) with a high electrode-density (25 electrodes/1.4 mm²) for both recording from active neurons and electrical stimulation of a population of neurons. Electrodes were fabricated using micromachining techniques. Geometrical features of these electrodes provide more contacts between the electrodes and targeted neural tissues. In order to achieve the proposed geometry, we introduce a novel masking method to coat variable-height electrodes with uniform and small tip-exposure that significantly improves process time and costs compared to conventional techniques. In the next step, the active sites of the electrodes were coated with thin-films of molybdenum (Mo) and platinum (Pt). The average impedance of Mo and Pt electrodes at 1 kHz was 350 ± 50 kΩ and 150 ± 10 kΩ, respectively.