Hidden dynamics in fast force curves: Transient Damping and Brownian-Driven Contact Resonance

TL;DR

This paper introduces a method to analyze transient dynamics in fast force curves from atomic force microscopy, revealing local mechanical properties and heterogeneities that are hidden in traditional static analysis.

Contribution

It presents a new interferometric detection technique and a harmonic oscillator model to extract local stiffness and dissipation from single force curves without external excitation.

Findings

Transient cantilever oscillations encode local mechanical properties.

Multiple interaction regimes are observable within a single force curve.

High-resolution mapping reveals heterogeneity and non-repeatability in samples.

Abstract

Force distance curves (FCs) are among the most direct measurements performed in atomic force microscopy (AFM), yet their information content is often reduced by filtering and quasi-static interpretation. Here, enabled by a new interferometric detector, we show that fast FCs inherently excite short-lived cantilever oscillations whose transient frequency and decay encode local stiffness and dissipation. By analyzing these dynamics on a single-curve, single-pixel basis, we extract time-local mechanical information without external broadband excitation or multi-pass imaging. We develop a state-dependent single-mode harmonic oscillator model that captures snap-in excitation, hydration-mediated dissipation, and contact stiffness during fast force mapping. Experimental analysis of high-bandwidth force-curve data and numerical simulations demonstrate that multiple dynamically distinct interaction regimes occur within a single FC. Accessing these transient dynamics enables high-throughput, high-resolution mapping of mechanical contrast and reveals heterogeneous and non-repeatable behaviors that are lost under conventional averaging or with conventional detection schemes with higher noise floors.