Mechanical effect of gold nanoparticles labeling used for biochemical sensor applications: A multimode analysis by means of SiNx micromechanical cantilever and bridge mass detectors

The effect on mechanical properties of monolithic SiNx micromechanical cantilever and bridge by the adsorption of gold colloids is reported by measuring their resonance frequency shifts. It is experimentally demonstrated that higher resonance modes are more sensitive to the added mass than the fundamental resonance mode leading to increased sensitivity. This is even more significant with monolithic SiNx bridge resonators due to the tensile stress within the SiNx layer. Indeed, resonance frequencies are about ten times higher than calculation without taking into account the tensile stress which was estimated at 500 MPa. Another important result is that the adsorbed colloids do not produce significant change in the stiffness of the SiNx micromechanical resonators. Hence, it is pointed out that only the added mass of Au colloid contributes to the change in the mechanical characteristics of the resonators. Sensitivities up to 20 Hz/pg can be obtained with a minimum detectable density of gold colloids about 2.6 x 10(-2) nanoparticles/mum(2). (C) 2004 American Institute of Physics.