Influence of microstructure-confined fluids on the atomic force microscope probe dynamics

Dynamics of atomic force microscope probes near a two-dimensional grating in deionised water were investigated to explore the influence of microstructure-probe confined fluids. Experiments demonstrate that the oscillation characteristics could be deviated on the step element and on the bottom element of the grating even with the same controlling parameters. The probe responses indicate that different hydrodynamic contributions are presented on different microstructures. The squeeze fluid-induced interaction stiffness is slightly repulsive and the damping increases monotonously with the decrease of probe-sample separation to the nanoscale. In addition, the viscous damping is greater at the bottom element than that at the step element, which is verified by fluid-structure coupled finite-element simulations.