A 3D flexible parylene probe array for multichannel neural recording

A 3D completely flexible probe array capable of multichannel neural recording at various depths in neural tissue has been developed. It was designed and fabricated based on a surface micro-machining process. Multichannel long-term stable neural recording is fundamental to allow the control of prosthetic devices and to investigate brain function. Numerous designs for electrodes have been developed and reported. However, none of them was able to obtain stable long-term multichannel recordings because most of them were based on rigid micromachining technology that relied on silicon, which can shift slightly in soft neural tissue. The electrode was fabricated on a 10μm-thick parylene substrate. It consists of six flexible needle-shaped probes (1.2mm in height, 160μm in width), each with three recording sites (20μm × 20μm) on the surface, and integrated cables. Because the electrode is completely flexible, it is less-invasive and has the potential to provide stable recordings over a long duration in soft and delicate neural tissue. This complete flexibility of the electrode is achieved with a combination of processes for surface micro-machining and folding. In addition, we propose a new method using PEG coating in order to insert these flexible probes into the neural tissue. In the evaluation experiment using gelatin, this probes were successfully inserted into the gelatin without fracture.