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Wilson, Jonathan M. A. (2024) Novel bi-layer coatings for the protection and functionalisation of magnesium-based medical alloys. PhD thesis, University of Nottingham.

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Abstract

Bioresorbable biomaterials represent a revolutionary class of materials in the field of biomedical engineering, offering solutions for various medical applications. Unlike traditional permanent implants, bioresorbable biomaterials are designed to degrade gradually within the body over time, eventually being absorbed and assimilated into the surrounding tissues without the need for surgical removal. Magnesium (Mg) and its alloys are promising candidates for

these applications due to their mechanical properties being similar to bone and the biological acceptance in the human body. However, their rapid degradation times are currently not practical for a vast array of clinical applications and as such a way to reduce the corrosion rate or delay the onset of Mg corrosion must be developed.

The work presented in this thesis demonstrates the development of a novel bilayered coating, consisting of an electrodeposited layer of calcium phosphate (CaP) and a layer of radio frequency magnetron sputtered (RFMS) phosphate-based glass (PBG), specifically to protect

and functionalise Mg WE43 alloy for bioresorbable biomedical applications. The microstructural development of the CaP layer was assessed as a function of duty cycle, deposition time and electrolyte pH, with the parameters of 0.6 duty cycle, 20 min deposition time and electrolyte pH 4.5 being taken forward for the addition of the PBG layer due to

achieving a brushite coating of ca. 7 – 8 µm thickness which improved cytocompatibility and corrosion rate of the alloy to 0.57 mm/Y. The PBG layer was varied by P content from 40 mol% to 30 mol% investigating the effects of novel “invert” glasses with the novel P30 glass achieving a significant cytocompatibility improvement over the Mg WE43 alloy and P40 glass whilst improving the corrosion rate. The ca. 0.5 µm thick PBG layer in combination with the CaP layer showed a successful improvement of cytocompatibility and corrosion rate with the P30 CaP coating being the most viable in terms of protection of the Mg WE43 alloy with an annealing effect occurring on the CaP layer during PBG deposition and exhibited corrosion properties Ecorr = -0.71 V, icorr = 0.032 mA/cm2 and corrosion rate 0.74 mm/Y. The coatings

were assessed using the combined complementary characterisation methods of scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray

diffractometry (XRD), X-ray photoelectron spectroscopy (XPS) and 2D profilometry. Further application testing was performed with an extraction test in Dulbecco’s Modified Eagles Medium (DMEM) media and potentiodynamic polarisation (PDP) testing in DMEM.

The novel bilayered coatings developed in this thesis have shown a successful improvement of the cytocompatibility and reduction of the corrosion rate of Mg WE43 alloy. Furthermore, the combination of both deposition methods has shown to be complimentary to each other and both tailorable for a variety of potential orthopaedic applications as bioresorbable biomaterials, providing a promising route for advancement in the biomaterials field.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Scotchford, Colin A. Grant, David M. Wadge, Matthew D.
Keywords:	Bioresorbable biomaterials; Biomedical engineering; Magnesium alloys; Corrosion rate; Cytocompatibility; Coatings
Subjects:	R Medicine > R Medicine (General) > R855 Medical technology. Biomedical engineering. Electronics
Faculties/Schools:	UK Campuses > Faculty of Engineering > Department of Mechanical, Materials and Manufacturing Engineering
Item ID:	79762
Depositing User:	Wilson, Jonathan
Date Deposited:	10 Dec 2024 04:40
Last Modified:	10 Dec 2024 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/79762

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