Purpose: To investigate the mechanical response of a silicon microprobe while it penetrates the optic nerve.
Methods: The finite element method was adopted to analyze models of the mechanical aspects of the silicon microprobe, including the effects of dimensions, the buckling load, lateral load, and the interaction between the microprobe and the tissue of the optic nerve. The silicon microprobe was fabricated based on silicon-on-insulator (SOI) wafer by micro-electro-mechanical system (MEMS) processing techniques.
Results: The designed microprobe shank was 750 µm long and 110 µm wide with thickness of 15 µm. Lateral barbs were included so as to decrease the stress at stimulating-site regions. The microprobe could withstand a 50 MPa vertical load on the shank tip before buckling, but was more likely to be damaged by a lateral load rather than a vertical one. The silicon microprobe was successfully fabricated by MEMS processing techniques based on a four-inch SOI wafer. Mechanical analysis of the interactions between shank and optic nerve tissue showed that the maximum stress changed during the process of the microprobe insertion.
Conclusions: A silicon microprobe was designed as a potential visual prosthesis to be used for optic nerve stimulation. The mechanical issues were analyzed by means of the finite element method, and the implantable microprobe was fabricated based on a silicon-on-insulator wafer to maintain a uniform thickness.