Comparative dynamics of magnetically, acoustically, and Brownian motion driven microcantilevers in liquids

Magnetic, acoustic, and thermal (Brownian motion induced) excitations are commonly used for dynamic atomic force microscopy (AFM) in liquids, yet the fundamental differences in microcantilever vibration response for these different excitations remain poorly understood. In this work we discuss theoretically and experimentally several major differences between the amplitude and phase response of magnetically, acoustically, and thermally excited cantilevers in liquids and propose a way to estimate quantitatively the unsteady structure-borne and fluid-borne excitation forces acting on the acoustically excited AFM cantilever. The results have significant implications both for amplitude and frequency modulated AFM operation in liquids.