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Microstructure of Selective Laser Melted 316L under Non-Equilibrium Solidification Conditions
(2023)
A special generative manufacturing (AM) process was developed for the partial integration of active ingredients into open-porous matrix structures. A mixture of a silver-containing solution as an antibacterial material with an alginate hydrogel as a carrier system was produced as the active ingredient. The AM process developed was used to introduce the active ingredient solution into an open-porous niobium containing a β-titanium matrix structure, thus creating a reproducible active ingredient delivery system. The matrix structure had already been produced in a separate AM process by means of selective laser melting (SLM). The main advantage of this process is the ability to control porosity with high precision. To determine optimal surface conditions for the integration of active ingredients into the matrix structure, different surface conditions of the titanium substrate were tested for their impact on wetting behaviour of a silver-containing hydrogel solution. The solution-substrate contact angle was measured and evaluated to determine the most favourable surface condition. To develop the generative manufacturing process, an FDM printer underwent modifications that permitted partial application of the drug solution to the structure in accordance with the bioprinting principle. The modified process enabled flexible control and programming of both the position and volume of the applied drug. Furthermore, the process was able to fill up to 95% of the titanium matrix body pore volume used. The customised application of drug carriers onto implants as a drug delivery system can be achieved via the developed process, providing an alternative to established methods like dip coating that lack this capability.
Additive Manufacturing is a highly innovative and pioneering process that offers among others a high degree of flexibility and complexity in terms of the part design or the possibility to integrate various functions in a single part. Therefore, it possesses great chances to establish itself as a significant method within the entire field of manufacturing processes in the near future. The used materials and their thermodynamic behavior determine the resulting properties of parts built in this way, but also by the generated microstructure. Regarding the whole process with its formation of a microscale melt and ongoing rapid solidification a variety of different microstructures can be created, which in turn can affect the mechanical as well as chemical properties and the long–term behavior to a great extent. Furthermore, it can be seen that different metals and alloys in combination with the process conditions can result in different and/or fluctuating qualities of the manufactured components. Nonetheless, additive manufacturing can lead to a noticeably enhancement of materials or products that were manufactured and processed with traditional methods so far and open new possibilities and perspectives in the research and development sector. However, this means that it is crucial to adapt currently used tests and methods to the new properties and manufacturing process.