Effect of biaxial curvature on the resonance frequency of uncoated microcantilevers

Abstract Microcantilevers (MCs) are extensively studied as physical, chemical and biological sensors in dynamic mode, where the shift in resonance frequency due to the adsorption of target analytes/biomolecules on their surface is measured. However, surface stress generated during adsorption or microfabrication induced curvature inherently present in MCs can influence the observed frequency shift, introducing significant errors in the quantification of the analyte sensing response. In spite of several studies over the past four decades, the role of surface stress/curvature on the stiffness and thus resonance frequency of MCs is not well established. Interestingly, this effect also depends on MC dimensions and is not completely understood. In the present work, we address this problem and demonstrate that the presence of transverse curvature significantly influences the resonance frequency and this effect critically depends on width by length ratio (W/L) of MCs. For this purpose, we have fabricated uncoated SiO2 MCs of various dimensions with inherent biaxial curvature. Our experiments on these devices revealed that when W/L of MCs is 0.4) was found to marginally reduce the observed frequency shift and is attributed to the presence of competing non-linear plate softening effects at these dimensions. Finally, we have compared our results with various experimental studies and theoretical models reported in the literature.