Deconvolution of dissipative pathways for the interpretation of tapping-mode atomic force microscopy from phase-contrast

Abstract

Phase-contrast in tapping-mode atomic force microscopy (TM-AFM) results from dynamic tip-surface interaction losses which allow soft and hard nanoscale features to be distinguished. So far, phase-contrast in TM-AFM has been interpreted using homogeneous Boltzmann-like loss distributions that ignore fluctuations. Here, we revisit the origin of phase-contrast in TM-AFM by considering the role of fluctuation-driven transitions and heterogeneous loss. At ultra-light tapping amplitudes <3 nm, a unique amplitude dependent two-stage distribution response is revealed, alluding to metastable viscous relaxations that originate from tapping-induced surface perturbations. The elastic and viscous coefficients are also quantitatively estimated from the resulting strain rate at the fixed tapping frequency. The transitional heterogeneous losses emerge as the dominant loss mechanism outweighing homogeneous losses at smaller amplitudes for a soft-material. Analogous fluctuation mediated phase-contrast is also apparent in contact resonance enhanced AFM-IR (infrared), showing promise in decoupling competing thermal loss mechanisms via radiative and non-radiative pathways. Understanding the loss pathways can provide insights on the bio-physical origins of heterogeneities in soft-bio-matter e.g., single cancer cell, tumors, and soft-tissues.

Understanding the Microstructure Connectivity in Photopolymerizable Aluminum-Phosphate-Silicate Sol–Gel Hybrid Materials for Additive Manufacturing

“…This is an amplitude-modulated technique in which the cantilever is driven by a fixed-amplitude sinusoidal signal . Conservative and non-conservative tip–surface interactions cause a phase shift, which reflects local changes in chemical and mechanical properties, − allowing the study of polymers, , conjugated materials, , and sol–gel hybrid materials. , …”

Theoretical and experimental study of phase optimization of tapping mode atomic force microscope

“…Therefore, it is significant to study the factors affecting phase-imaging theoretically and experimentally. [21,[24][25][26][27][28] The dependence of phase contrast on elastic interaction and inelastic interaction in TM-AFM have been investigated. [21] Some results have revealed the relationships between the phase images and the amplitude values of the free oscillation A 0 and the setpoint amplitude A SP .…”

“…[21] Some results have revealed the relationships between the phase images and the amplitude values of the free oscillation A 0 and the setpoint amplitude A SP . [24][25][26] Fasolk et al found that the selecting of the appropriate temperature levels for the phase scanning according to the characteristics of the samples can improve the phase contrast results. [27] Furthermore, a large number of studies have shown that energy dissipation is the key factor affecting the phase imaging of TM-AFM.…”

Molecular dynamics models of tapping mode atomic force microscopy

“…In this way, the TM-AFM is able to calculate the mechanical properties of the sample, and thus characterize the sample. analysis of the soft and hard characteristics of a sample [5].Accurate measurement of the mechanical properties of a sample is an important method for sample characterization; with an accurate mechanical model established and verified, TM-AFM can accurately measure the mechanical properties. In TM-AFM, an oscillating nano-scale cantilevered probe is brought near the surface of a sample; the proximity and oscillation amplitude are adjusted so the probe taps the surface during each cycle; the tapping force is indirectly controlled using as feedback the change in probe amplitude at each tap.…”

“…In this way, the TM-AFM is able to calculate the mechanical properties of the sample, and thus characterize the sample. analysis of the soft and hard characteristics of a sample [5].…”