Microreactors in Organic Chemistry and Catalysis, Second Edition (2013)
2. Fabrication of Microreactors Made from Metals and Ceramic
2.4. Generative Method: Selective Laser Melting
A special method to manufacture metallic microstructures is the selective laser melting. It is one of the rare generative methods for metals and normally included into the rapid prototyping technologies. The technique is completely different from the abrasive techniques described so far. On a base platform made of the desired metal material, a thin layer of a metal powder is distributed. A focused laser beam is channeled along structure lines given by a 3D CAD model, controlled by a computer. During the laser exposure, the metal powder melts, forming a welding bead. The first layer of welding beads forming a copy of the 3D CAD structure is generated. After this, the platform is lowered by a certain value, new powder is distributed, and the process is repeated. Thus, microstructures are generated layer by layer. In principle, any metal powder can be used for SLM, as long as the melting temperature can be reached with the laser. For metal alloys, some problems with dealloying by the melt might occur. Details of this relatively new technology can be found in Refs [19–21]. In Figure 2.9, a schematic of the working principle of this technique is provided, while Figure 2.10 shows a picture of a microstructure stainless steel body manufactured by SLM.
Figure 2.9 Schematic sketch of the selective laser melting technology for metals.
Figure 2.10 Photo and details of a stainless steel microstructure cube, generated by SLM. Clearly, the single-welding beads are shown, which have been generated layer by layer to form the walls.