Probing of Polymer Surfaces in the Viscoelastic Regime

Chyasnavichyus, Marius; Young, Seth L.; Tsukruk, Vladimir V.

doi:10.1021/la404925h

Cited by 94 publications

(90 citation statements)

References 85 publications

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“…Recently, Chyasnavichyus et al. (60) used a Johnson-modified Sneddon (55) approach in a combination with the standard linear solid model to describe the viscoelastic behavior of polymers. Because appropriate models to describe the situation of unloading correctly, i.e., where the contact radius decreases, are cumbersome and often require numerical solutions, most researchers use the method of Oliver and Pharr (61) that allows the evaluation of mechanical properties by concentrating on the earliest stages of the unloading curve, where the restoring material behavior is assumed to be purely elastic and the contact area not yet decreasing.…”

Section: Methodsmentioning

confidence: 99%

Viscoelastic Properties of Confluent MDCK II Cells Obtained from Force Cycle Experiments

Brückner

Nöding

Janshoff

2017

Biophysical Journal

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The local mechanical properties of cells are frequently probed by force indentation experiments carried out with an atomic force microscope. Application of common contact models provides a single parameter, the Young’s modulus, to describe the elastic properties of cells. The viscoelastic response of cells, however, is generally measured in separate microrheological experiments that provide complex shear moduli as a function of time or frequency. Here, we present a straightforward way to obtain rheological properties of cells from regular force distance curves collected in typical force indentation measurements. The method allows us to record the stress-strain relationship as well as changes in the weak power law of the viscoelastic moduli. We derive an analytical function based on the elastic-viscoelastic correspondence principle applied to Hertzian contact mechanics to model both indentation and retraction curves. Rheological properties are described by standard viscoelastic models and the paradigmatic weak power law found to interpret the viscoelastic properties of living cells best. We compare our method with atomic force microscopy-based active oscillatory microrheology and show that the method to determine the power law coefficient is robust against drift and largely independent of the indentation depth and indenter geometry. Cells were subject to Cytochalasin D treatment to provoke a drastic change in the power law coefficient and to demonstrate the feasibility of the approach to capture rheological changes extremely fast and precisely. The method is easily adaptable to different indenter geometries and acquires viscoelastic data with high spatiotemporal resolution.

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Section: Methodsmentioning

confidence: 99%

Viscoelastic Properties of Confluent MDCK II Cells Obtained from Force Cycle Experiments

Brückner

Nöding

Janshoff

2017

Biophysical Journal

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“…The program performs a spectroscopy curve similar to the program provided with [22], except for the introduction of the 2D surface Young’s modulus for the description of in-plane surface forces, as described in the first section of the Results and Discussion above. The code is based on trimodal excitation of the cantilever, whose simulation has been described in previous publications [14,22–23], and is thus not repeated here. The code uses constant-frequency, constant-amplitude excitation of the active eigenmodes, although other schemes or imaging modalities, such as scanning, can be implemented.…”

Section: Resultsmentioning

confidence: 99%

Nanoscale effects in the characterization of viscoelastic materials with atomic force microscopy: coupling of a quasi-three-dimensional standard linear solid model with in-plane surface interactions

Solares

2016

Beilstein J. Nanotechnol.

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SummarySignificant progress has been accomplished in the development of experimental contact-mode and dynamic-mode atomic force microscopy (AFM) methods designed to measure surface material properties. However, current methods are based on one-dimensional (1D) descriptions of the tip–sample interaction forces, thus neglecting the intricacies involved in the material behavior of complex samples (such as soft viscoelastic materials) as well as the differences in material response between the surface and the bulk. In order to begin to address this gap, a computational study is presented where the sample is simulated using an enhanced version of a recently introduced model that treats the surface as a collection of standard-linear-solid viscoelastic elements. The enhanced model introduces in-plane surface elastic forces that can be approximately related to a two-dimensional (2D) Young’s modulus. Relevant cases are discussed for single- and multifrequency intermittent-contact AFM imaging, with focus on the calculated surface indentation profiles and tip–sample interaction force curves, as well as their implications with regards to experimental interpretation. A variety of phenomena are examined in detail, which highlight the need for further development of more physically accurate sample models that are specifically designed for AFM simulation. A multifrequency AFM simulation tool based on the above sample model is provided as supporting information.

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“…which was also reported by Lee and Radok. 15 Further Analytical Developments: Linear Load Assumption If the load history -during the contact of the cantilever tip with the sample -is assumed to grow linearly with a constant slope ( _ F Þ according to F t ð Þ5 _ F t, an assumption that may hold in some circumstances during the approach portion of a force spectroscopy experiment, 28,29 then eq 5 reduces to:…”

Section: Equation 3 Can Be Conveniently Laplace Transformedmentioning

confidence: 99%

Calculation of standard viscoelastic responses with multiple retardation times through analysis of static force spectroscopy AFM data

López-Guerra

Eslami

Solares

2017

J Polym Sci B Polym Phys

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We explore the physics of an atomic force microscopy (AFM) cantilever tip interacting with a generalized viscoelastic sample containing an arbitrary number of characteristic times, when the cantilever's base is driven with constant velocity toward the sample. This mode of operation, often called static force spectroscopy (SFS), can be harnessed to thoroughly analyze time-dependent viscoelastic information frequently overlooked in experiments. We generalize the solution of previous authors who have studied the standard linear solid model, and offer a solution applicable to any linear viscoelastic model. This generalization is crucial for the prediction of the model's response over wide ranges of time-scale. As a demonstration, successful predictions of harmonic functions (e.g., loss tangent) over a wide frequency range are obtained through analysis of simulated SFS results. In addition, we show that analysis through the generalized solution and previous expressions is no longer valid when the force does not grow linearly in time, so we also deliver an alternate route for extracting the viscoelastic information, which does not rely on the force linearity assumption. Despite the large amount of theoretical content (included for theoretical rigor's sake), the practical user can also benefit from the new procedures offered and the corresponding explanations.

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Probing of Polymer Surfaces in the Viscoelastic Regime

Cited by 94 publications

References 85 publications

Viscoelastic Properties of Confluent MDCK II Cells Obtained from Force Cycle Experiments

Viscoelastic Properties of Confluent MDCK II Cells Obtained from Force Cycle Experiments

Nanoscale effects in the characterization of viscoelastic materials with atomic force microscopy: coupling of a quasi-three-dimensional standard linear solid model with in-plane surface interactions

Calculation of standard viscoelastic responses with multiple retardation times through analysis of static force spectroscopy AFM data

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