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Issue 40, 2016
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Measuring the viscoelastic creep of soft samples by step response AFM

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Abstract

We have measured the creep response of soft gels and cells after applying a step in loading force with atomic force microscopy (AFM). By analysing the creep response data using the standard linear solid model, we can quantify the viscous and elastic properties of these soft samples independently. Cells, in comparison with gels of similar softness, are much more viscous, as has been qualitatively observed in conventional force curve data before. Here, we quantify the spring constant and the viscous damping coefficient from the creep response data. We propose two different modes for applying a force step: (1) indirectly by increasing the sample height or (2) directly by employing magnetic cantilevers. Both lead to similar results, whereas the latter seems to be better defined since it resembles closely a constant strain mode. The former is easier to implement in most instruments, and thus may be preferable from a practical point of view. Creep analysis by step response is much more appropriate to analyse the viscoelastic response of soft samples like cells than the usually used force curve analysis.

Graphical abstract: Measuring the viscoelastic creep of soft samples by step response AFM

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Publication details

The article was received on 03 Apr 2016, accepted on 30 Aug 2016 and first published on 31 Aug 2016


Article type: Paper
DOI: 10.1039/C6SM00801A
Soft Matter, 2016,12, 8297-8306

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    Measuring the viscoelastic creep of soft samples by step response AFM

    A. Yango, J. Schäpe, C. Rianna, H. Doschke and M. Radmacher, Soft Matter, 2016, 12, 8297
    DOI: 10.1039/C6SM00801A

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