Nanoindentation and nano-scratching of hydroxyapatite coatings for resorbable magnesium alloy bone implant applications

Patrick Lemoine; Jonathan Acheson; Stephen McKillop; Jeroen Jjp van den Beucken; Joanna Ward; Adrian Boyd; Brian J Meenan

doi:10.1016/j.jmbbm.2022.105306

Nanoindentation and nano-scratching of hydroxyapatite coatings for resorbable magnesium alloy bone implant applications

J Mech Behav Biomed Mater. 2022 Sep:133:105306. doi: 10.1016/j.jmbbm.2022.105306. Epub 2022 Jun 7.

Authors

Patrick Lemoine¹, Jonathan Acheson², Stephen McKillop², Jeroen Jjp van den Beucken³, Joanna Ward², Adrian Boyd², Brian J Meenan²

Affiliations

¹ Nanotechnology and Integrated Bioengineering Centre (NIBEC), School of Engineering, Ulster University, United Kingdom. Electronic address: p.lemoine@ulster.ac.uk.
² Nanotechnology and Integrated Bioengineering Centre (NIBEC), School of Engineering, Ulster University, United Kingdom.
³ Regenerative Biomaterials, Dentistry, Radboud UMC, NL-6525, EX, Nijmegen, the Netherlands.

PMID: 35717775
DOI: 10.1016/j.jmbbm.2022.105306

Abstract

The corrosion rate of Mg alloys is currently too high for viable resorbable implant applications. One possible solution is to coat the alloy with a hydroxyapatite (HA) layer to slow the corrosion and promote bone growth. As such coatings can be under severe stresses during implant insertion, we present a nano-mechanical and nano-tribological investigation of RF-sputtered HA films on AZ31 Mg alloy substrates. EDX and XRD analysis indicate that as-deposited coatings are amorphous and Ca-deficient whereas rapid thermal annealing results in c-axis orientation and near-stoichiometric composition. Analysis of the nanoindentation data using a thin film model shows that annealing increases the coating's intrinsic hardness (H) and strain at break (H/E) values, from 2.7 GPa to 9.4 GPa and from 0.043 to 0.079, respectively. In addition, despite being rougher, the annealed samples display better wear resistance; a sign that the rapid thermal annealing does not compromise their interfacial strength and that these systems have potential for resorbable bone implant applications.

Keywords: Hydroxyapatite; Magnesium alloy; Nanoindentation; Nanotribology; Resorbable bone implant.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Alloys / chemistry
Coated Materials, Biocompatible / chemistry
Corrosion
Durapatite* / chemistry
Magnesium* / chemistry
Materials Testing
Surface Properties

Substances

Alloys
Coated Materials, Biocompatible
Durapatite
Magnesium