Measuring the elastic modulus of soft biomaterials using nanoindentation
Measuring the elastic modulus of soft biomaterials using nanoindentation
The measurement of the elastic modulus of soft biomaterials via nanoindentation relies on the accurate determination of the zero-point of the tip-sample interaction on which the depth of penetration into the sample is based. Non-cantilever based nanoindentation systems were originally designed for hard materials, and therefore monitoring the zero-point contact presents a significant challenge for the characterisation of very soft biomaterials. This study investigates the ability of non-cantilever based nanoindentation to differentiate between hydrogels with elastic moduli on the order of single kiloPascals (kPa) using a bespoke soft contact protocol and low flexural stiffness of instrument. Polyethylene glycol (PEG) hydrogels were fabricated as a model system with a range of elastic moduli by varying the polymer concentration and degree of crosslinking. Elastic modulus values were calculated using the Oliver-Pharr method, Hertzian contact model, as well as a viscoelastic model to account for the time-dependent behaviour of the gels. The stiffness measurements were validated by measuring cantilever beams with the equivalent flexural stiffness to that of the PEG hydrogels being tested. The results demonstrated a high repeatability of the measurements, enabling differentiation between hydrogels with elastic moduli in the single kPa to hundreds of kPa range.
Elastic modulus, Hydrogel, Nanoindentation, Soft materials, Stiffness
Xu, Dichu
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Harvey, Terence
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Begiristain, Eider
e13eec7d-168c-4253-8269-e665b1befa69
Domínguez, Cristina
58bd9094-2e83-43b3-81c8-04dc16590e0c
Sánchez-abella, Laura
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Browne, Martin
6578cc37-7bd6-43b9-ae5c-77ccb7726397
Cook, Richard
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September 2022
Xu, Dichu
e91ddedf-af9a-4f0c-834b-3e538c2e166b
Harvey, Terence
3b94322b-18da-4de8-b1af-56d202677e04
Begiristain, Eider
e13eec7d-168c-4253-8269-e665b1befa69
Domínguez, Cristina
58bd9094-2e83-43b3-81c8-04dc16590e0c
Sánchez-abella, Laura
d9853c74-c5cc-4e32-a4dd-776f57ac632a
Browne, Martin
6578cc37-7bd6-43b9-ae5c-77ccb7726397
Cook, Richard
06f8322d-81be-4f82-9326-19e55541c78f
Xu, Dichu, Harvey, Terence, Begiristain, Eider, Domínguez, Cristina, Sánchez-abella, Laura, Browne, Martin and Cook, Richard
(2022)
Measuring the elastic modulus of soft biomaterials using nanoindentation.
Journal of the Mechanical Behavior of Biomedical Materials, 133, [105329].
(doi:10.1016/j.jmbbm.2022.105329).
Abstract
The measurement of the elastic modulus of soft biomaterials via nanoindentation relies on the accurate determination of the zero-point of the tip-sample interaction on which the depth of penetration into the sample is based. Non-cantilever based nanoindentation systems were originally designed for hard materials, and therefore monitoring the zero-point contact presents a significant challenge for the characterisation of very soft biomaterials. This study investigates the ability of non-cantilever based nanoindentation to differentiate between hydrogels with elastic moduli on the order of single kiloPascals (kPa) using a bespoke soft contact protocol and low flexural stiffness of instrument. Polyethylene glycol (PEG) hydrogels were fabricated as a model system with a range of elastic moduli by varying the polymer concentration and degree of crosslinking. Elastic modulus values were calculated using the Oliver-Pharr method, Hertzian contact model, as well as a viscoelastic model to account for the time-dependent behaviour of the gels. The stiffness measurements were validated by measuring cantilever beams with the equivalent flexural stiffness to that of the PEG hydrogels being tested. The results demonstrated a high repeatability of the measurements, enabling differentiation between hydrogels with elastic moduli in the single kPa to hundreds of kPa range.
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Accepted/In Press date: 18 June 2022
e-pub ahead of print date: 21 June 2022
Published date: September 2022
Additional Information:
Funding Information:
This work was supported by funding from the European Union (EU) within its Horizon 2020 programme, project MDOT (Grant Agreement 814654 ).
Funding Information:
The authors would like to thank Adrian Harris (Micro Materials Ltd.) for the help with the nanoindentation testing. The authors are grateful to Dr Damien Dupin (CIDETEC) for proofreading the article. This work was supported by funding from the European Union (EU) within its Horizon 2020 programme, project MDOT (Grant Agreement 814654 ).
Publisher Copyright:
© 2022 The Authors
Keywords:
Elastic modulus, Hydrogel, Nanoindentation, Soft materials, Stiffness
Identifiers
Local EPrints ID: 468038
URI: http://eprints.soton.ac.uk/id/eprint/468038
ISSN: 1751-6161
PURE UUID: 03160b81-2a0a-4aec-aa2c-03c2eb57bc08
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Date deposited: 28 Jul 2022 16:47
Last modified: 17 Mar 2024 03:18
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Author:
Eider Begiristain
Author:
Cristina Domínguez
Author:
Laura Sánchez-abella
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