Abstract
In this work, a standard CMOS process is used to integrate sensing circuits and MEMS structures to form capacitive biosensors. The sensing interface areas are formed without requiring post-CMOS micromachining processes, leading to convenient fabrication. Surface modification and functionalization can be performed for detection of a variety of biological molecules or bacteria viruses. This chip contains an array of interdigitated microelectrodes for capacitive sensing, in which the coated silicon dioxide on top is used for biomolecule immobilization. Anti-streptavidin antibody is used in this work, which is immobilized on chip surface while magnetic microbeads coated with streptavidin are driven to the sensing sites for specific binding. This is the major difference from conventional biosensors using target antigen and complementary antibody. On-chip inductors produce electromagnetic forces to attract microbeads to the center of each microcoil, where microelectrodes are located, for capacitive detection. Capacitance change due to magnetic beads remaining on the chip after specific binding is successfully demonstrated with an 8×8microcoil and capacitive sensor array.