Effect of surface stress on microcantilever resonance frequency during water adsorption: influence of microcantilever dimensions

This paper reports the effect of dimensions of microcantilever (MC) on its resonance frequency and bending upon adsorption of water molecules. Study is conducted on three MCs having the dimensions of 450×40×2.5 μm3 (MC1), 225×30×3 μm3 (MC2) and 125×35×4.5 μm3 (MC3). The measured resonant frequency showed the expected negative shift in MC1, initially positive followed by a negative shift in MC2 and only positive shift in MC3 during adsorption. This behavior is attributed to changes in the stiffness of the MC associated with the surface stress. The surface stress generated on the MC has been derived from its bending measurements upon water adsorption. The change in the stiffness of MC evaluated from an independent estimate of expected frequency shift showed that the relative stiffness change of MC increases linearly with the surface stress scaled with cube of width to height ratio of MCs, confirming the dimensional dependence of adsorption induced stiffness change.