Study Of Micro Electrode Array For Retinal Prosthesis

The success of the cochlear implant is often cited when making the case for the feasibility of the replacement of defective tissue by electric device. However, retinal prosthesis is far more complex and difficult than the cochlear implant. If any part of the visual pathway, including eye, retina, optical nerve, and cortical layer, goes wrong, the vision will be lost. The two most common outer retinal degenerative diseases are age-related macular degeneration (AMD) and retinitis pigmentosa (RP). A number of treatments have shown some effectiveness in slowing the progression of AMD, but no cure exists for AMD or RP. The implantation of Micro device to restore the sight could be a potential way to resolve this problem.MEMS technology is a kind of micro manufacture technology which develops along with silicon micro manufacture technology. By fabrication process such as photolithograph, we can manufacture device in micro or nano dimension. In recent years, Flexible MEMS and Bio-MEMS have emerged. Based on flexible substrate, device in micrometer dimension can be fabricated by MEMS technology, and these devices can bear impact and can be curved. In vitro diagnostic device and vivo implanted device, Bio-MEMS technology can provide edges as well. Based on MEMS technology and the structure of retina, we first design the configuration of the micro electrode array which is fabricated on flexible substrate. The fabricated electrode array is 4×5 grid, covering a 3 mm×4 mm area. Each electrode is 100μm in diameter.In our study, we used standard MEMS fabrication technology which involves sputtering, photolithography, etching, and electroplating. We also realized three different fabrication processes, analyzed and optimized the process. The best impedance of a single electrode tested in 0.9% saline solution is 750k～7kΩ, at the frequency from 0.1Hz to 100 kHz. In the following vivo animal experiment, EEP (Electrical evoked cortical potentials) is gained.