Fabrication of pyramid-shaped three-dimensional flexible microelectrode array for improved neural interfacing

Electrode-tissue interfacing is critical for effective implementation of neural recording or stimulation. In this paper, we report a pyramid-shaped three-dimensional (3D) flexible microelectrode array for the purpose of achieving improved electrode-tissue interfacing for retinal stimulation. The pyramid-shaped flexible microelectrode was fabricated through a novel fabrication process, in which an electrochemical-based sacrificial layer (aluminum) was deposited to facilitate the removal of the photoresist remaining in the silicon mold pits. The geometrical and electrical properties of the microelectrode were investigated by the scanning electron microscope (SEM) and the electrochemical measurement, respectively. The measured electrode impedance of the pyramid-shaped microelectrodes is about 2 times lower than that of the conventional planar microelectrodes (2D) with the same base area. The applicability of this 3D electrode for rabbit's retinal stimulation was demonstrated. This novel 3D electrode array can be a promising candidate for retinal prosthesis.