High sensitivity piezoresistive cantilever sensor for biomolecular detection

Micro-cantilevers are now gaining popularity in biomolecular sensing. Monitoring and mass detection of biological species can be accurately determined using the micro- or nano- scale cantilevers. The targeted biological molecules are first immobilized onto the microcantilever which is later determined through static or dynamic techniques. Optical detection method is employed to determine the deflection of the cantilever in static analysis or the shift of resonance frequency in dynamic analysis. Though both analyses using optical detection have been highly sensitive and produce accurate results, they required extensive and expensive experimental setup and are not practical for point-of-care application. Piezoresistive sensing has become an alternative approach in biological sensing as changes in mechanical properties can be converted to electrical output. This paper presents the design and simulation of a highly sensitivity piezoresistive based micro-cantilever for biomolecular detection. A series of holes are formed on the silicon based micro-cantilever. These discontinuities form the Stress Concentration Region (SCR) used to increase sensitivity for piezoresistive sensing. Finite Element Analysis (FEA) through ANSYS 8.0 was performed on the structural model to maximize the SCR so as to improve the sensitivity of the cantilever. The optimized number, geometry, radius, and the distance from the first hole to the root of these holes were discussed in this paper.