Modeling viscoelasticity through spring-dashpot models in intermittent-contact atomic force microscopy.

Enrique A López-Guerra,Santiago D Solares

doi:10.3762/bjnano.5.224

Abstract

We examine different approaches to model viscoelasticity within atomic force microscopy (AFM) simulation. Our study ranges from very simple linear spring–dashpot models to more sophisticated nonlinear systems that are able to reproduce fundamental properties of viscoelastic surfaces, including creep, stress relaxation and the presence of multiple relaxation times. Some of the models examined have been previously used in AFM simulation, but their applicability to different situations has not yet been examined in detail. The behavior of each model is analyzed here in terms of force–distance curves, dissipated energy and any inherent unphysical artifacts. We focus in this paper on single-eigenmode tip–sample impacts, but the models and results can also be useful in the context of multifrequency AFM, in which the tip trajectories are very complex and there is a wider range of sample deformation frequencies (descriptions of tip–sample model behaviors in the context of multifrequency AFM require detailed studies and are beyond the scope of this work).

Highlights

Atomic force microscopy (AFM) has evolved rapidly since its invention in the mid-1980s [1] and has been used since for measuring topography and probe–sample forces on micro- and nanoscale surfaces in different environments
Different approaches to model viscoelasticity within intermittent contact AFM have been studied with special emphasis on spring–dashpot models
We summarize the models that have been frequently used in AFM, highlighting their strengths and deficiencies

Summary

Introduction

Atomic force microscopy (AFM) has evolved rapidly since its invention in the mid-1980s [1] and has been used since for measuring topography and probe–sample forces on micro- and nanoscale surfaces in different environments. Tapping mode AFM (amplitude modulation, AM-AFM) is the most common dynamic method and has been the subject of thorough studies [2,3,4,5,6]. In tapping mode AFM damage or wear of the tip and surface are reduced with respect to contact-mode AFM due to lower friction and lateral forces, which makes it more applicable for imaging soft samples, such as polymers and biological surfaces. Tapping mode AFM has the additional advantage that it records a phase contrast simultaneously with the acquisition of topography, which can be very useful in the study of heterogeneous samples [7,8,9,10].

Methods

Results

Conclusion