FLEXIBLE NEURAL PROBE INTEGRATED MICROCHANNEL AND OPTICAL FIBER FOR MULTIFLE STIMULATION

Abstract

In this study, we report a neural probe which can achieve optical stimulation though aligned optical fiber with fiber guide, chemical stimulation though micro-channel and extracellular neural signal recording though platinum electrodes. Especially, all of the micro-channel, fiber guide and shank parts were fabricated of the biocompatible and flexible polymer SU-8. Therefore, this probe can reduce neuronal damage during probe insertion compared with Si-based neural probe [2]. Figure 1 shows the schematic view of the proposed neural probe structure. The micro-channel formed of SU-8 is integrated top of the shank [3]. A fiber guide formed by SU-8 has a space for etched optical fiber to be aligned easily. There are 4-channel platinum electrodes, in the vicinity of the stimulation site to monitor extracellular neural signals during the optical stimulation. In this proposed structure, total length, width and thickness of shank are about 8mm, 200μm and 65μm, respectively. Figure 2 shows the fabrication process of the proposed neural probe using MEMS technology. Above all, first SU-8 layer is coated and patterned on silicon wafer for the probe shank. Next, chrome and gold were deposited and patterned for interconnections and wire bonding. Titanium and platinum were deposited and patterned for recording electrodes. Next, second SU-8 layer is formed as the electrical isolation layer. first and second SU-8 layer were hard baked for perfect polymerization. After that, third SU-8 layer is formed as the fiber guide and micro-channel layer, and fourth SU-8 layer is formed as the cover of micro-channel. Finally, SU-8 layer is released with dry etching (DRIE). For optical characterization of the fabricated probe, the etched optical fiber is connected to an external light source with 473nm wavelength, and the light has been successfully transmitted to the end of the probe tip for optical stimulation.