Oscillatory nanoindentation of highly compliant hydrogels: a critical comparative analysis with rheometry

Akhtar, R., Draper, E. R. , Adams, D. J. and Hay, J. (2018) Oscillatory nanoindentation of highly compliant hydrogels: a critical comparative analysis with rheometry. Journal of Materials Research, 33(8), pp. 873-883. (doi: 10.1557/jmr.2018.62)

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We present a method for measuring the shear complex modulus of hydrogels by oscillatory nanoindentation, with unprecedented attention to procedure and uncertainty analysis. The method is verified by testing a typical low-molecular-weight gelator formed from the controlled hydrolysis of glucono-δ-lactone. Nanoindentation results are compared with those obtained by rheometry using both vane-in-cup and parallel-plate fixtures. At 10 Hz, the properties measured by oscillatory nanoindentation were G′ = 38.1 ± 2.8 kPa, tan δ = 0.22 ± 0.02. At the same frequency, the properties measured by rheometry were G′ = 15.3 ± 2.9 kPa, tan δ = 0.11 ± 0.016 (vane-in-cup) and G′ = 7.9 ± 1.1 kPa, tan δ = 0.05 ± 0.004 (parallel-plate). The larger shear modulus measured by nanoindentation is due to the scale of testing. Whereas rheometry characterizes the bulk material response, nanoindentation probes the fibrous network of the gel. The procedure and analysis presented here are valuable for nanoindentation testing of other compliant materials such as hydrogels, soft biological tissue, and food products.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Draper, Emily and Adams, Dave
Authors: Akhtar, R., Draper, E. R., Adams, D. J., and Hay, J.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Journal of Materials Research
Publisher:Cambridge University Press
ISSN (Online):2044-5326
Published Online:27 April 2018
Copyright Holders:Copyright © 2018 Materials Research Society
First Published:First published in Journal of Materials Research 33(8): 873-883
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
571341Liquid-liquid transitions in molecular liquids: from supramolecular structure to phase separationKlaas WynneEngineering and Physical Sciences Research Council (EPSRC)EP/J004790/1CHEM - CHEMISTRY
697461Mapping and controlling nucleationKlaas WynneEngineering and Physical Sciences Research Council (EPSRC)EP/N007417/1CHEM - CHEMISTRY
768041Multicomponent Supramolecular HydrogelsDave AdamsEngineering and Physical Sciences Research Council (EPSRC)EP/L021978/2SCHOOL OF CHEMISTRY