Quantitative analysis and decoupling of mass and stiffness effects in cantilever mass sensors

Response of nanomechanical resonant mass sensors to adsorption does not only depend on the mass loading, but also on the adsorbate stiffness, adsorption induced surface stresses and location. It is therefore clear that with just resonance frequency measurement, decoupling the stiffness and the mass effects is difficult. A recent theory proposed using the electrostatic pull-in instability (EPI), in combination with the resonance frequency to decouple the aforementioned opposing effects, is presented hereof. In this paper, by performing experiments of adsorption on cantilevers, we 1) performed preliminary experiments on EPI stiffness measurement and show the stiffness effects of typical mass deposition, 2) show that EPI can be used in combination with the frequency measurements, to quantitatively analyze both the stiffness and the mass of the adsorbed material.