Measuring Viscoelasticity of Soft Samples Using Atomic Force Microscopy

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
S. Tripathy ◽  
E. J. Berger
Keyword(s):  
Atomic Force Microscopy ◽  
Soft Tissues ◽  
Relaxation Times ◽  
Indentation Test ◽  
Strain History ◽  
Force Microscopy ◽  
Afm Indentation ◽  
Atomic Force ◽  
Dependent Part ◽  
Soft Samples

Relaxation indentation experiments using atomic force microscopy (AFM) are used to obtain viscoelastic material properties of soft samples. The quasilinear viscoelastic (QLV) model formulated by Fung (1972, “Stress Strain History Relations of Soft Tissues in Simple Elongation,” in Biomechanics, Its Foundation and Objectives, Prentice-Hall, Englewood Cliffs, NJ, pp. 181–207) for uniaxial compression data was modified for the indentation test data in this study. Hertz contact mechanics was used for the instantaneous deformation, and a reduced relaxation function based on continuous spectrum is used for the time-dependent part in the model. The modified QLV indentation model presents a novel method to obtain viscoelastic properties from indentation data independent of relaxation times of the test. The major objective of the present study is to develop the QLV indentation model and implement the model on AFM indentation data for 1% agarose gel and a viscoelastic polymer using spherical indenter.

Phase Contrast Imaging in Atomic Force Microscopy

1997 ◽  
Vol 3 (S2) ◽  
pp. 1275-1276
Author(s):  
Sergei Magonov
Keyword(s):  
Atomic Force Microscopy ◽  
Phase Contrast ◽  
Phase Changes ◽  
Phase Imaging ◽  
Phase Detection ◽  
Contrast Imaging ◽  
Force Microscopy ◽  
Atomic Force ◽  
Resonance Frequencies ◽  
Soft Samples

Phase detection in TappingMode™ enhances capabilities of Atomic Force Microscopy (AFM) for soft samples (polymers and biological materials). Changes of amplitude and phase changes of a fast oscillating probe are caused by tip-sample force interactions. Height images reflect the amplitude changes, and in most cases they present a sample topography. Phase images show local differences between phases of free-oscillating probe and of probe interacting with a sample surface. These differences are related to the change of the resonance frequency of the probe either by attractive or repulsive tip-sample forces. Therefore phase detection helps to choose attractive or repulsive force regime for surface imaging and to minimize tip-sample force. For heterogeneous materials the phase imaging allows to distinguish individual components and to visualize their distribution due to differences in phase contrast. This is typically achieved in moderate tapping, when set-point amplitude, Asp, is about half of the amplitude of free-oscillating cantilever, Ao. In contrast, light tapping with Asp close to Ao is best suited for recording a true topography of the topmost surface layer of soft samples. Examples of phase imaging of polymers obtained with a scanning probe microscope Nanoscope® IIIa (Digital Instruments). Si probes (225 μk long, resonance frequencies 150-200 kHz) were used.

Probing Micromechanical Properties of the Extracellular Matrix of Soft Tissues by Atomic Force Microscopy

2016 ◽  
Vol 232 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Ignasi Jorba ◽  
Juan J. Uriarte ◽  
Noelia Campillo ◽  
Ramon Farré ◽  
Daniel Navajas
Keyword(s):  
Extracellular Matrix ◽  
Atomic Force Microscopy ◽  
Soft Tissues ◽  
Force Microscopy ◽  
Micromechanical Properties ◽  
Atomic Force

Correction of Microrheological Measurements of Soft Samples with Atomic Force Microscopy for the Hydrodynamic Drag on the Cantilever

Langmuir ◽  
2002 ◽  
Vol 18 (3) ◽  
pp. 716-721 ◽  
Author(s):  
J. Alcaraz ◽  
L. Buscemi ◽  
M. Puig-de-Morales ◽  
J. Colchero ◽  
A. Baró ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Hydrodynamic Drag ◽  
Force Microscopy ◽  
Atomic Force ◽  
Soft Samples

scholarly journals Modeling viscoelasticity through spring–dashpot models in intermittent-contact atomic force microscopy

2014 ◽  
Vol 5 ◽  
pp. 2149-2163 ◽  
Author(s):  
Enrique A López-Guerra ◽  
Santiago D Solares
Keyword(s):  
Atomic Force Microscopy ◽  
Stress Relaxation ◽  
Relaxation Times ◽  
Dissipated Energy ◽  
Force Microscopy ◽  
Fundamental Properties ◽  
Creep Stress ◽  
Atomic Force ◽  
Linear Spring ◽  
Intermittent Contact

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).

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

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Arindam Phani ◽  
Ho Sang Jung ◽  
Seonghwan Kim
Keyword(s):  
Atomic Force Microscopy ◽  
Phase Contrast ◽  
Soft Tissues ◽  
Loss Mechanism ◽  
Tapping Mode ◽  
Force Microscopy ◽  
Atomic Force ◽  
Single Cancer ◽  
Nanoscale Features ◽  
Mode Atomic Force Microscopy

AbstractPhase-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.

Atomic Force Microscopy of Soft Samples: Gelatin and Living Cells

1998 ◽  
pp. 178-193 ◽  
Author(s):  
Jan Domke ◽  
Christian Rotsch ◽  
Paul K. Hansma ◽  
Ken Jacobson ◽  
Manfred Radmacher
Keyword(s):  
Atomic Force Microscopy ◽  
Living Cells ◽  
Force Microscopy ◽  
Atomic Force ◽  
Soft Samples

An Atomic Force Microscopy Indentation Study of Biomaterial Properties

2005 ◽  
Author(s):  
E. J. Berger ◽  
S. Tripathy ◽  
K. Vemaganti ◽  
Y. M. Kolambkar ◽  
H. X. You ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Soft Materials ◽  
Data Interpretation ◽  
Close Relative ◽  
Small Scale ◽  
Force Microscopy ◽  
Afm Indentation ◽  
Atomic Force ◽  
Biomechanical Investigation ◽  
Series Type

Atomic force microscopy (AFM) is a powerful and increasingly common modality of biomechanical investigation, including imaging, force spectroscopy, and microrheology. AFM indentation of biomaterials requires use of a contact model for data interpretation and material property extraction, and a large segment of the scientific community uses the Hertz model or a close relative for small-scale indentation of thin, soft materials in high strain applications. We present experimental results and analytical/numerical modeling which lead to two main conclusions: (i) Hertzian mechanics are useful in a surprisingly large parameter range, including scenarios in which the underlying assumptions are seemingly violated, and (ii) the Hertz solution serves as a useful base from which power-series type solutions can be derived for a variety of non-Hertzian effects.

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