Three-dimensional (3D) printing is a form of additive manufacturing. In 3D printing, three-dimensional structures are built by putting down a thin layer of material and building additional layers on top. 3D printed plastics have been commonly used for more than two decades. Initially these were made from special resins and used for physical mock-ups of product designs to see a representation of the final product, determine the feel of a product, or to check the fit between interconnecting parts. Later, new equipment was developed that was capable of producing parts using engineering grade plastics like ABS (acrylonitrile butadiene styrene). 3D printing continues to advance with new innovations being constantly developed. Three of the relatively recent developments are 3D metal printing, low-cost plastic printing, and 3D printing of living cells to produce artificial organs.
3D metal printing resolve the problem of previous methods that are printed in plastic. Metals including stainless steel, aluminum, and titanium can be 3D printed and used directly in applications. Although 3D metal printing has its own special limitation, it also overcomes some of the limitation of subtractive manufacturing methods like milling or turning. Internal flow cavities can be produced that are impossible to machine using tools that must access the part from the outside. Complex geometry can be produced with a single program and does not require multiple set-up and fixturing operations. Tool-cutting paths do not need to be calculated. The printing path can be obtained directly from the 3D CAD (computer aided design) model. Moreover, CAD models for human body parts can be extracted from 3D scans of the human body using existing medical technology such as computed tomography (CT) or magnetic resonance imaging (MRI). This leads to the potential development of customized implants that exactly match the needs of the patient.
Recent release of low-cost 3D plastic printers has had a significant impact on innovation. Before these devices were available, 3D printed parts could only be produced using high cost equipment with expensive resins. The cost of these prototypes was at least 50 times the cost to produce one using these new low-cost devices. Maker spaces providing printing services to students have sprung up in universities. Accuracy of these devices is lower than the professional grade models, but they are often sufficient for mock-ups and evaluations of design concepts. Students with little 3D computer aided design experience especially benefit from making a prototype. It allows for several low-cost design iterations to be produced before investing in an actual machined prototype or a usable part produced with advanced 3D printing technology. Experienced CAD designers will benefit less from these devices, because they will be better able to visualize the completed product and perform iterative design optimization while still in the 3D CAD environment. These low-cost devices are also useful for inventors and entrepreneurs. Using this technology, low cost mock-ups can be produced to show to potential investors during the pitch.
3D bioprinting is a process where living cells are laid down layer by layer. Because cells are small they can pass easily thorough orifices designed for printing with other materials. The use of 3D bioprinting is one of the greatest opportunities in the field of regenerative medicine. However, there are still challenges that need to be overcome before this technology can be used to print a large replacement organ. The fluid’s viscosity must be low enough to pass through the small orifice for fine resolution printing, but the viscosity also much be sufficiently high for the organ to retain shape after printing. Furthermore, the 3D printing process is slow (even using traditional printing materials). This causes additional problems, because the cells must be kept alive during the printing process that may require hours or days to complete. Finally, a sufficient vascular network must be produced to supply the cells with nutrients and oxygen and remove waste. This can be particularly challenging because, it will require an extensive network due to the inherently low diffusion distance of oxygen (150 μm).
