Current Research Directions in 3D Printing in Medicine

Abstract

3D printing for biomedical applications seems to be a technology that is developing in a wavelike manner. Not long after the first attempts for computer-aided design and manufacturing (CAD/CAM) were made in fields such as mechanical engineering and design, researchers also tried to apply these new possibilities in medicine. Only a few years later, the first patient-specific implants, for example, for the treatment of skull defects, became available. While in the very beginning subtractive technologies such as computerized numeric controlled milling were still used, soon new options for additive manufacturing (AM) started to take off [1]. For biomedical applications, laser-based methods such as selective laser sintering (SLS) or 3D powder printing were mostly used, both of which were mostly limited in the beginning to metals and ceramic materials, respectively. A very important step therefore was the development of fused deposition modeling (FDM) as the first extrusion-based AM technology using polymeric materials. For biomedical applications, manufacturing of porous 3D scaffolds with defined outer and inner morphology and their utilization in tissue engineering was investigated in detail, using FDM of poly(lactic acid) or polycaprolactone. These polymers were also among the first biodegradable materials successfully applied in AM. Probably because of the limitations concerning the applicable materials (most early AM machines could only be operated with a few different materials) and the high price of the devices, even at the beginning of the 21st century only a few groups further investigated AM technologies for medical applications. But the situation has changed dramatically since a variety of cheaper 3D printers have become available, of which many can handle different types of materials, offering the necessary flexibility for new developments. In addition, the breakthrough concerning integration of living cells in the printing process (‘bioprinting’) was achieved using ink-jet as well as extrusion-based technologies, opening up the possibility to directly generate artificial tissues. We have therefore seen a strong increase of publications in the field of 3D printing in medicine in the last couple of years, coming from researchers from all over the world, accompanied by new conferences, solely focused on this topic. Nevertheless, we are still at the beginning of a huge and strong development and nobody knows what will become possible in the future. In my opinion, the following directions are those with the strongest driving force at the moment: