Detection of Abrin Using a Polyrnide-based Piezoresistive Microcantilever Biosensor

Although the traditional silicon-based microcantilever working with intrinsic piezoresistive effect has high sensitivity, it is easier to be broken in practical application because of its high elastic modulus. In this paper, we develop a piezoresistive microcantilever with a flexible polymide (PI) layer, whose Young's modulus is only about one-tenth of silicon oxide, as the top insulator of the single-crystalline silicon piezoresistor. The polymide-based piezoresistive microcantilever was fabricated on a SOI wafer and the experimental output voltage fluctuation of the fabricated microcantilevers in the phosphate buffered saline (PBS) solution is within 2 V at 3V bias voltage supply. Finally, a sensitive detection of abrin toxin was realized with a limit of detection of 30ng/mL (0.01M) by modifying the anti-abrin PcAb on the top gold surface of the microcantilever. Due to the fact that the fabrication process is compatible with CMOS, it provides a promising possibility to monolithically integrate the piezoresistive microcantilever biosensor with SOT CMOS circuits.