Selective laser sintering/melting of nitinol–hydroxyapatite composite for medical applications

Abstract

The layer-by-layer synthesis of 3D parts from nitinol (NiTi intermetallide) and hydroxyapatite additions using selective laser sintering/melting (SLS/SLM) is studied. The effect of different laser parameters on the structure and phase composition of sintered/melted samples is analyzed with optical and scanning electron microscopy, x-ray diffraction, and energy-dispersive x-ray analysis. Optimum SLS/SLM parameters are determined for the synthesis of NiTi + HA to be used in tissue engineering and manufacture of medical devices (pins, nails, porous implants, drug delivery systems). No significant destruction of HA ceramics under laser treatment is observed. The amount of nickel released to the surface of 3D parts decreases owing to the additional oxidation of free titanium during SLS/SLM and the formation of a protective HA layer. Full-density 3D parts are produced from nitinol by SLM including preheating to 300°C.

Laser and Electron Beam Additive Manufacturing Methods of Fabricating Titanium Bone Implants

“…There is also the possibility of preheating in SLM systems. This works either by setting an additional laser to preheat the powder to temperatures below its melting point [35] or to adjust the building table temperature to a commercially-available maximum of 300 • C [36]. SLM machines use argon atmosphere to prevent sample oxidation, but there is a possibility to perform a process in a controlled atmosphere to enhance the mechanical properties of fabricated material [37].…”

Laser additive manufacturing of bulk and porous shape-memory NiTi alloys: From processes to potential biomedical applications

“…For example, SLM has been used to manipulate NiTi properties by adding hydroxyapatite (an excellent bone bioactive material) to produce a composite for biomedical applications. 79 Furthermore, LMD has been utilized to produce a ductile and wear-resistant in situ TiB 2 /NiTi coating (to increase durability of Ti-6Al-4V alloy) from a powder mixture of Ni + TiB 2 + Ti 80 , 81 or even to generate a functionally graded Ti-NiTi to customize corrosion and mechanical behavior. 82 These are promising aspects that can potentially improve the effi ciency of functional components.…”

Electrodeposition of a hydroxyapatite coating on a biocompatible NiTi alloy

“…2 Research efforts have been directed to the elimination of Ni release from the surface and therefore improving the corrosion resistance and as well as the biocompatibility of the implants. [1][2][3][4][5] Nickel is known for its diverse effects on human body, including allergic reactions and toxicity. 6 Studies on commercially available orthodontic wires showed increased Ni release rate with time of exposure and type of solution, indicating the need for better understanding the processes at the interface between the implant and biological environment.…”

“…2,7 Various surface modification techniques have been used including mechanical, chemical and thermal treatments, as well as bioactive coatings such as calcium phosphate coatings. 4,5,8,9 Hydroxyapatite coatings (HAP) are appropriate candidates for biocompatibility improvement since they offer an excellent surface for cell growth. 8,10 However, they cannot be used in load-bearing applications due to their poor mechanical properties.…”

“…Different methods for the deposition of hydroxyapatite coatings are known, such as plasma spraying, electrophoretic deposition, sol-gel deposition, ion beam deposition and electrochemical deposition. 4,[10][11][12][13] Electrochemical deposition has the advantage of uniform coating formation, low cost, room temperature and simple setup. 14 In this paper, the electrodeposition of hydroxyapatite coating on the surface of NiTi alloy was conducted.…”