Study Of A Multi-Channel Stimulating Microelectrode Array For Visual Prosthesis Based On MEMS Technology

By implanting a neural microelectrode into human body on specific areas, it can treat some diseases which traditional drugs or surgery can't treat, such as Parkinson disease, epilepsy, paralysis, abnormal muscle tone, the senile dementia, the incontinence, defibrillators abnormal, deaf and blind, etc. Recently, research efforts worldwide are developing implanted visual prostheses aimed at restoring vision for the blind. As one part of the visual prostheses, the implanted microelectrode array (MEA) is the direct interface between the external electronic circuit system and the nerve tissue, it plays an important role in the system of vision restoration. With the rapid development of micro-electro-mechanical systems (MEMS) technology in recent years, research of multichannel stimulating MEA based on MEMS technology draw widespread attention.The main research contents of this thesis include:(1) We designed and fabricated a muti-channel flexible implanted MEA for the suprachoroidal electrical stimulation based on MEMS technology. The MEA was arranged by 6×10 with additional 4 optional return electrodes, and a single electrode was 350μm in diameter. Photosensitive polyimide (PSPI) instead of traditional non-photo sensitive polyimide or parylene was chosen as the substrate and insulating material, platinum (Pt) was served as the conducting material for the electrodes owing to its high charge delivery capacity and chemical inertness in the physiological environment. We developed a double-layer metallization process technology for interconnecting lines which realized the higher density electrodes and reduced the interconnecting-part width in comparison with a single-layer fabrication process. To avoid the cracking problem existing in the platinum-PI structure, a Ti intermediate layer and oxygen plasma were introduced to retard the tendency.(2) The MEA was evaluated in vitro and in vivo. In vitro, an automatic three-electrode test system was used to measure the electrochemical impedance spectroscopy (EIS) of the MEA. The charge storage and injected capacity were respectively identified by cyclic voltammetry (CV) and Voltage Transients. In vivo, EEP waveforms could be consistently recorded by implanting the MEA in rabbit suprachoroidal location and the spatial spread maps of EEP indicated that the stimulating sites were topological to the response areas on the visual cortex. The results indicated that the MEA was suitable for long-term safe suprachoroidal stimulation, and could be considered as a potential visual prosthesis.