Design Of MEMS-based Piezoresistive Micro-cantilever Biosensor

Piezoresistive micro-cantilever biosensor is based on the achievements of many fields, including MEMS, IC, Nanotechnology, molecular biology and material science. These biosensors can be easily fabricated with the MEMS technology. The antibody (on the magnetic bead)-antigen (in the cancer cell) specific binding occurred on the cantilever surface results in cantilever bending and piezoresistance change, which can be measured by the Wheatstone Bridge. Then the detection of cancer cell with high sensitivity is accomplished.The system design and implementing method of reusable piezoresistive micro- cantilever biosensor for cancer detecting are discussed in the thesis. The emphases are the optimization design of the micro-electromagnetic and layout design and process design. Aiming at the optimization design of U-shaped cantilever-based biosensor, expressions for predicting sensitivity and resolution are derived by combining stress distribution with power densities of noise. This thesis also reports a comprehensive theoretical analysis and finite element analysis (FEA) of the magnetic field due to current flowing in the planer micro-electromagnetic. The relationship of the magnetic field and the structural parameters of the micro- electromagnetic is presented. In addition, the expression of magnetic force acting on the magnetic beads has been derived from simple electromagnetic theory. The equation shows that the magnetic force depends on both the magnetic filed strength and the magnetic field. From the relationship listed above, the geometry parameters of micro-electromagnetic are optimized in order that the magnetic bead can be immobilized efficiently.The introduction of the fabrication process of the biosensor includes the single- crystal silicon processes and SOI processes. The biosensor would be fabricated from SOI wafers that were used for reducing the thickness of the cantilevers because the buried oxide (BOX) layer of SOI wafers provides the etch stop. Layout design and process design based on SOI processes are made according to the Specification of the MEMS line in China electronics technology group the 13th research institute.