Study Of Silicon MEMS Based Two Dimensions Biomedical Microprobe Array

Recently, the technology of microelectrode has been one of the most crucialtechnologies in research of information exhibition and transition in inner neuralsystem. Not only it can help finding the position of neural cell, but also is a majormethod in research of information conduction and organization between the cluster ofneural cells. Eventually, the technology of microelectrode plays an import part inspace direction of neural clinic chirurgery. Microelectrode array based onmicroelectro-mechanical system(MEMS) technology is one of important applicationsin biomedicine and brings a new means in biomedicine field. The prospect for thedevelopment of microelectrode technology in precision drug injection, clinicalmonitoring and biochemistry test, artificial limb rehabilitation and neural prosthesis isbroad. It can provide painless, effective and save biomedical method in accordancewith human requirements.In this paper, a silicon microelectrode array based on MEMS technology isdesigned. This array consists of four individual parallel shafts each with fourrecording electrode sites. The circuit model of the cell-electrode interface has beendone before this microelectrode array design. Based on this model, we give somequalitative analysis of the electrical parameters about the microelectrode and designthe structure and size .Silicon bulk-micromachining fabrication technology of the microelectrode arrayis investigated regarding the lab situation, and the fabrication process is designed andoptimized with special considerations on multi-size structure, technology monitordiagram, etc. According to this fabrication process, the microelectrode array is madesuccessfully. After the microelectrode array is fabricated successfully ,we analysesome problems in the process. In order to get a good silicon probe tip shape, someanisotropic and isotropic wet etching is carried out.To meet the demand of test, two encapsulations of aluminum wire ultrasonicbonding and gold bump soldering are designed and tested. The frequency dependenceof microelectrode impedance was tested in 0.9% saline solution at room temperatureby 3-point measurements with an Agilent 4284A LCR meter. The magnitude of theelectrode impedance is 1.3 M Ohm at 1 kHz , which is consistent with neuralrecording applications. Some experiments in bullfrog sciatic tissues also gets a goodresult.All the test results indicate that this microelectrode is successful. But this projectis just underway and many problems and works need to be done.