Over the past few years, additive manufacturing - better known as 3D printing - has become established as a driver of innovation in a wide variety of industries. In addition to the many industrial applications - for example for the production of prototypes and spare parts - there are many benefits to using 3D printing for the medical sector. The applications of additive manufacturing since the beginning of their use in the medical field have been just as varied as the production possibilities and materials themselves. The fact that 3D printing is especially suitable for the production of prototypes or one-off individual parts made it possible to use it early on, in the field of implant production amongst other things. The benefits of additive manufacturing in the medical sector, the potential applications that are already commonplace and also the significance of 3D printing for medicine in the future will all be examined in more detail in this whitepaper.
To get an overview of the applications of additive manufacturing in medicine, it is first necessary to understand how the 3D printing process works. Basically, additive manufacturing differs from other manufacturing methods in that the particular material being worked on is not cast, such as in the manufacture of injection moulded parts, or cut from a larger block, as is the case for example with CNC machining. As the term "additive" suggests, in additive manufacturing material is applied layer by layer. Even if the individual additive methods differ in the precise process and the materials, the process of layered production of the workpiece is still the same. Unlike other manufacturing processes, with this method there is great freedom in terms of the design of parts and possible geometries. Since the early days and the initial hype about this new production process, 3D printing has seen a great deal of differentiation, so current manufacturing processes differ greatly. The most important manufacturing processes used in the manufacture of medical products today are direct metal laser sintering and stereolithography.
Direct metal laser sintering (DMLS)
DMLS is particularly suitable for printing parts made of metals and special alloys. In principle, the procedure for printing parts by DMLS hardly differs from the familiar methods of additive manufacturing. To print metals, support structures are required to dissipate the heat generated during the manufacturing process and to
ensure the stability of the components. Without support structures there would also be a risk that new material would be simply wiped away during the printing process. In DMLS, the metal is in the form of a powder in a bath and is processed using a laser. The laser melts a cross sectional layer of the final workpiece, which means that the powder becomes a solid shape. In the next step, the baseplate on which this process takes place is lowered by a precise distance and a new layer of metal powder is distributed by the printer on the build platform. This process is repeated layer by layer until finally the finished component, such as an implant, emerges. After the component is completed, it is released from the support structures and the excess metal powder is post-processed depending on its application. A large number of metals are suitable for production using DMLS including titanium alloys, which are important for medicine - in particular the production of bone implants.
Stereolithography is comparable to other additive manufacturing methods. It is mainly used for the printing of polymers and plastics with complex geometries or very small structures that require a particular rigidity, impact resistance or durability. As with DMLS, this process uses a laser to do the actual printing. Unlike DMLS, however, the material is not in the form of powder in the working area, but in the form of a resin consisting of photopolymers and additives. An ultraviolet laser hardens this resin to a thermosetting plastic. Here, too, the construction platform is lowered at each work stage, ensuring that a new layer of the resin covers the component which is then hardened into the required shape by the laser. After the component has been produced layer by layer, the remnants of the resin are cleaned off in post processing and supporting structures are removed. After an additional treatment to harden off the materials, the component is then ready for its intended purpose. New material MicroFine Green, which can be printed using stereolithography, is ideal for use in medicine. Since it is possible to produce particularly fine, high-resolution structures, medical applications such as miniaturised catheters or minimally invasive tools are potential applications.