Proximity effect on hydrodynamic interaction between a sphere and a plane measured by Force Feedback Microscopy at different frequencies

TL;DR

This study uses Force Feedback Microscopy to measure viscous damping, stiffness, and static forces in a sphere-plane liquid interaction across various frequencies, revealing proximity effects in hydrodynamic interactions at the nanoscale.

Contribution

It introduces a method to simultaneously measure static force, stiffness, and dissipation in sphere-plane geometry using FFM across a broad frequency range.

Findings

Measured viscous damping and stiffness over a large frequency range.

Demonstrated the capability of FFM to perform nano-scale surface force measurements.

Compared FFM results with traditional Surface Force Apparatus measurements.

Abstract

In this article, we measure the viscous damping $G'',$ and the associated stiffness $G',$ of a liquid flow in sphere-plane geometry in a large frequency range. In this regime, the lubrication approximation is expected to dominate. We first measure the static force applied to the tip. This is made possible thanks to a force feedback method. Adding a sub-nanometer oscillation of the tip, we obtain the dynamic part of the interaction with solely the knowledge of the lever properties in the experimental context using a linear transformation of the amplitude and phase change. Using a Force Feedback Microscope (FFM)we are then able to measure simultaneously the static force, the stiffness and the dissipative part of the interaction in a broad frequency range using a single AFM probe. Similar measurements have been performed by the Surface Force Apparatus with a probe radius hundred times bigger. In this context the FFM can be called nano-SFA.