Surface Modification of Biometals by Plasma-Based Technology

Project: Research

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Plasma immersion ion implantation and deposition (PIII&D), an efficient non-line-of-sightsurface modification technique especially suitable for samples with a complex geometry, hasmany commercial applications in microelectronics, metallurgy, and biomedical engineering. ThePlasma Laboratory in City University of Hong Kong is considered one of the most advancedresearch laboratories of its kind in the world having attracted more than 80 research projectsworth US$ 18 million, established extensive research ties with universities and researchinstitutions world-wide, and published more than 1,200 refereed journal papers (over 22,000citations). However, PIII&D has some limitations in biomedical applications. For instance,owing to the practical limits on implantation voltage, the modified layer is typically quite thinthereby raising doubts on long term durability of the materials especially in orthopedic anddental applications in which some abrasion and fretting are expected. Moreover, unlikemicroelectronic or optoelectronic applications, the implanted ion species and fluences must bephysiologically safe. Hence, rigorous screening, design, and optimization are needed. In thisproject, we propose to combine PIII&D with surface nano-functionalization to address twoimportant orthopedic and dental applications of biometals, namely improving the antibacterialproperties of titanium and corrosion resistance of biodegradable magnesium.Titanium alloys are promising biomaterials for bone repair and reconstruction due to the goodmechanical properties. However, metallic materials often integrate poorly with host tissuesresulting in post-operation infection and it is important to design biomaterials that induce normalcell functions while simultaneously suppressing bacteria adherence and biofilm formation. Bycombining nanotechnology with PIII&D, a special surface can be produced on titanium-basedmaterials on which osteoblasts can attach and proliferate while the long-term antibacterialcapability is simultaneously enhanced. By embedding the appropriate amount of antibacterialagents at different depths by PIII&D, controlled and sustained release of the antimicrobialspecies can be achieved producing long-term effects up to six months and longer. Energetic ionbombardment and surface nano-functionalization are also expected to yield synergistic effects onthe surface biocompatibility.Natural biodegradability is a prominent advantage of magnesium alloys in biomedicalapplications such as bone fixation devices and cardiovascular stents. Mg alloys can providetemporary mechanical support during healing and then degrade naturally thereby obviating theneed for a second surgery to remove the implants. However, owing to the high chemicalreactivity, excessively fast degradation leads to premature loss of mechanical strength as well aschemical and biological problems such as evolution of hydrogen and high local pH. Hence, it isimperative to design and construct a temporary surface on Mg alloys to satisfy multiple clinicalrequirements such as mechanical strength, biocompatibility, and degradation rate. PIII&D is anideal technique to introduce the desirable elements to a proper depth to produce this temporarysurface and by performing surface mechanical attrition treatment (SMAT) prior to PIII&D, thethickness of the modified layer can be increased to tens of micrometers to meet most clinicalrequirements.The expected outcome of this project includes novel and commercially viable plasma immersiontechnology and surface-modified biometals with enhanced properties.


Project number9042228
Grant typeGRF
Effective start/end date1/01/167/05/19

    Research areas

  • Plasma immersion ion implantat,Biodegradable magnesium alloys,Titanium alloys,Surface corrosion,