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- Amin Yavari, S., et al.
(författare)
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Layer by layer coating for bio-functionalization of additively manufactured meta-biomaterials
- 2020
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Ingår i: Additive Manufacturing. - : Elsevier BV. - 2214-8604 .- 2214-7810. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing has facilitated fabrication of complex and patient-specific metallic meta-biomaterials that offer an unprecedented collection of mechanical, mass transport, and biological properties as well as a fully interconnected porous structure. However, applying meta-biomaterials for addressing unmet clinical needs in orthopedic surgery requires additional surface functionalities that should be induced through tailor-made coatings. Here, we developed multi-functional layer-by-layer coatings to simultaneously prevent implant-associated infections and stimulate bone tissue regeneration. We applied multiple layers of gelatin- and chitosan-based coatings containing either bone morphogenetic protein (BMP)-2 or vancomycin on the surface of selective laser melted porous structures made from commercial pure Titanium (CP Ti) and designed using a triply periodic minimal surface (i.e., sheet gyroid). The additive manufacturing process resulted in a porous structure and met the the design values comparatively. X-ray photoelectron spectroscopy spectra confirmed the presence and composition of the coating layers. The release profiles showed a continued release of both vancomycin and BMP-2 for 2–3 weeks. Furthermore, the developed meta-biomaterials exhibited a very strong antibacterial behavior with up to 8 orders of magnitude reduction in both planktonic and implant-adherent bacteria and no signs of biofilm formation. The osteogenic differentiation of mesenchymal stem cells was enhanced, as shown by two-fold increase in the alkaline phosphatase activity and up to four-fold increase in the mineralization of all experimental groups containing BMP-2. Eight-week subcutaneous implantation in vivo showed no signs of a foreign body response, while connective tissue ingrowth was promoted by the layer-by-layer coating. These results unequivocally confirm the superior multi-functional performance of the developed biomaterials.
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| 5. |
- Dadbakhsh, Sasan, et al.
(författare)
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Effect of Layer Thickness in Selective Laser Melting on Microstructure of Al/5wt.%Fe2O3 Powder Consolidated Parts
- 2014
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Ingår i: The Scientific World Journal. - : Hindawi Limited. - 1537-744X .- 2356-6140. ; 2014, s. 10-
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Tidskriftsartikel (refereegranskat)abstract
- In situreaction was activated in the powder mixture of Al/5 wt.%Fe2O3by using selective laser melting (SLM) to directly fabricate aluminium metal matrix composite parts. The microstructural characteristics of thesein situconsolidated parts through SLM were investigated under the influence of thick powder bed, 75 μm layer thickness, and 50 μm layer thickness in various laser powers and scanning speeds. It was found that the layer thickness has a strong influence on microstructural outcome, mainly attributed to its impact on oxygen content of the matrix. Various microstructural features (such as granular, coralline-like, and particulate appearance) were observed depending on the layer thickness, laser power, and scanning speed. This was associated with various material combinations such as pure Al, Al-Fe intermetallics, and Al(-Fe) oxide phases formed afterin situreaction and laser rapid solidification. Uniformly distributed very fine particles could be consolidated in net-shape Al composite parts by using lower layer thickness, higher laser power, and lower scanning speed. The findings contribute to the new development of advanced net-shape manufacture of Al composites by combining SLM andin situreaction process.
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| 10. |
- Dadbakhsh, Sasan, et al.
(författare)
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Heat treatment possibilities for an in situ βTi-TiC composite made by laser powder bed fusion
- 2020
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Ingår i: Additive Manufacturing. - : Elsevier. - 2214-8604 .- 2214-7810. ; 36
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Tidskriftsartikel (refereegranskat)abstract
- After laser powder bed fusion (LPBF) of an ultra-strong in situ TiC whisker reinforced β-Ti composite, this paper investigates the evolution of microstructure and mechanical properties in response to heat treatment at different temperatures. Using in depth nano-SEM and TEM analyses, it is shown that ageing at 400 °C rounds the whiskers, annihilates the strain fields and grows Mo segregated nano-cells, but without improving the ductility. In contrast, ageing at 600 °C enables the transformation of metastable β to a lamellar β + α, leading to a dual phase matrix embedding TiC particles. This is in such a manner that extra ageing at 600 °C coalesces the nano-lamellar α + β microstructure to form a coarser micro-lamellar α + β matrix. This microstructure achieves 66 % of the compressive deformation of Cp-Ti, and over 1400 MPa compressive strength after 1 h of ageing at 600 °C. Despite this success under compression, hard and stiff TiC particles may still cause large spherical fractured voids, severely limiting the plastic deformation under tension.
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