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A two-step method for rate-dependent nano-indentation of hydrogels.

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Title: A two-step method for rate-dependent nano-indentation of hydrogels.
Authors: Simič, Rok1, Mathis, Christian H.1, Spencer, Nicholas D.1 nspencer@ethz.ch
Source: Polymer. Feb2018, Vol. 137, p276-282. 7p.
Subjects: Hydrogels, Atomic force microscopy, Nanochemistry, Viscoelasticity, Permeability
Abstract: Soft, biphasic materials such as hydrogels are commonly used to mimic lubrication and confinement mechanics of biological tissue such as articular cartilage or the cornea. In-depth understanding of such mechanics is crucial for designing synthetic replacements for cartilage, contact-lens materials or soft coatings for medical devices. Using colloidal-probe atomic force microscopy (AFM), surfaces can be investigated at the nanoscale and information on the contact modulus, poro-viscoelastic properties and the permeability can be extracted. Yet, probing the surface of a soft material in a liquid environment is challenging, since the point of contact between a probe and sample surface during finite-rate indentation can be obscured by viscous squeeze-out effects of temporarily confined liquid. To address this issue, we have developed a 2-step indentation method that enables accurate alignment of finite-rate indentation curves with respect to the contact point of quasi-static indentation of soft matter in liquid. In this work, the issue and the method are illustrated by measurements on a commonly used poly(acrylamide) (PAAm) hydrogel. We have shown that liquid squeeze-out may cause non-negligible force offsets that can result in false contact-point determination during finite-rate indentation. The presented method allows accurate alignment of the indentation curves, enables one to accurately study the rate-dependent contact moduli and related stiffening effects, and thus greatly facilitates mechanical characterization of both biological as well as synthetic soft materials. [ABSTRACT FROM AUTHOR]
Copyright of Polymer is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
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DbLabel: Engineering Source
An: 127762612
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PubType: Academic Journal
PubTypeId: academicJournal
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  Data: A two-step method for rate-dependent nano-indentation of hydrogels.
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  Data: <searchLink fieldCode="AR" term="%22Simič%2C+Rok%22">Simič, Rok</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Mathis%2C+Christian+H%2E%22">Mathis, Christian H.</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Spencer%2C+Nicholas+D%2E%22">Spencer, Nicholas D.</searchLink><relatesTo>1</relatesTo><i> nspencer@ethz.ch</i>
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  Data: <searchLink fieldCode="JN" term="%22Polymer%22">Polymer</searchLink>. Feb2018, Vol. 137, p276-282. 7p.
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  Data: <searchLink fieldCode="DE" term="%22Hydrogels%22">Hydrogels</searchLink><br /><searchLink fieldCode="DE" term="%22Atomic+force+microscopy%22">Atomic force microscopy</searchLink><br /><searchLink fieldCode="DE" term="%22Nanochemistry%22">Nanochemistry</searchLink><br /><searchLink fieldCode="DE" term="%22Viscoelasticity%22">Viscoelasticity</searchLink><br /><searchLink fieldCode="DE" term="%22Permeability%22">Permeability</searchLink>
– Name: Abstract
  Label: Abstract
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  Data: Soft, biphasic materials such as hydrogels are commonly used to mimic lubrication and confinement mechanics of biological tissue such as articular cartilage or the cornea. In-depth understanding of such mechanics is crucial for designing synthetic replacements for cartilage, contact-lens materials or soft coatings for medical devices. Using colloidal-probe atomic force microscopy (AFM), surfaces can be investigated at the nanoscale and information on the contact modulus, poro-viscoelastic properties and the permeability can be extracted. Yet, probing the surface of a soft material in a liquid environment is challenging, since the point of contact between a probe and sample surface during finite-rate indentation can be obscured by viscous squeeze-out effects of temporarily confined liquid. To address this issue, we have developed a 2-step indentation method that enables accurate alignment of finite-rate indentation curves with respect to the contact point of quasi-static indentation of soft matter in liquid. In this work, the issue and the method are illustrated by measurements on a commonly used poly(acrylamide) (PAAm) hydrogel. We have shown that liquid squeeze-out may cause non-negligible force offsets that can result in false contact-point determination during finite-rate indentation. The presented method allows accurate alignment of the indentation curves, enables one to accurately study the rate-dependent contact moduli and related stiffening effects, and thus greatly facilitates mechanical characterization of both biological as well as synthetic soft materials. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Polymer is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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      – Type: doi
        Value: 10.1016/j.polymer.2018.01.017
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      – Code: eng
        Text: English
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        PageCount: 7
        StartPage: 276
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      – SubjectFull: Hydrogels
        Type: general
      – SubjectFull: Atomic force microscopy
        Type: general
      – SubjectFull: Nanochemistry
        Type: general
      – SubjectFull: Viscoelasticity
        Type: general
      – SubjectFull: Permeability
        Type: general
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      – TitleFull: A two-step method for rate-dependent nano-indentation of hydrogels.
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            NameFull: Mathis, Christian H.
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            NameFull: Spencer, Nicholas D.
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              Text: Feb2018
              Type: published
              Y: 2018
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