Fundamentals of 3D printing and its applications in biomedical engineering

Abstract

Three-dimensional (3D) printing is a practical manufacturing method that allows us to transform objects designed in the digital environment into physical objects using layered manufacturing methods. The terms of rapid prototyping and additive manufacturing are also used to express the manufacturing process using 3D printers. Unlike the subtractive manufacturing (machining) approach in which 3D objects are constructed by successively cutting material away from a solid block of material, additive manufacturing processes produce parts by adding material one layer at a time. In 3D printing technology, parts with complex geometries can be manufactured using less material compared to conventional manufacturing techniques. There is no need for molding in 3D printing, and the production of a part with different geometry can be quickly adapted. Objects designed in a digital environment can be directed to the production process immediately. Three-dimensional printing, which is very suitable for the production of objects with free-form surfaces, has been widely used in the medical sector, especially in the production of patient-specific biomedical devices [1]. Three-dimensional printing applications are spreading rapidly in many areas of the medical sector. Nowadays, orthopedic implants, prostheses, orthoses, dental products, anatomical models, customized tablets for personalized medicine, and many surgical instruments can be produced using 3D printers [2–5]. Three-dimensional printing allows significant flexibility for the fabrication of biomedical devices, offering geometric freedom without limitations experienced in traditional manufacturing methods. By using the 3D printing method, we are able to print complex shaped functional parts with detailed internal features and adjust the material density to produce lighter biomedical devices with fewer parts. Since the biomedical devices and implants must be compatible with the patient’s anatomy, the production of such devices by traditional manufacturing methods is a challenging task. In addition, because these devices are supposed to be designed for patient-specific purposes, the design of each item should be independently carried out for each patient [6]. Three-dimensional printing technology does not require additional production stages such as production line installation and mold design, thereby having the advantage of manufacturing the parts immediately, which makes the 3Dprintingmethod very suitable for the production of biomedical devices. Three dimensional printing has been one of the widely preferred approaches in the biomedical sector because of its high geometrical accuracy and resolution. In addition, the ability to print complex body implants by taking into account the magnetic resonance image (MRI) [7] and computed tomography (CT) [8] data further increased the functionality of this technology. Three-dimensional bioprinting is another application area of the 3D printing technology in which the complex 3D living tissues and artificial organs are constructed [9]. It is possible to produce 3D functional and living tissues using 3D bioprinting [10]. These printers generally use materials such as hydrogel, silicon, and protein solutions. The major aim in this field is to produce functional and transplantable human organs in the near future [11]. Some disadvantages of the 3D printing method are (i) it is not economically feasible for mass production, (ii) size of the part to be manufactured is limited to the dimensions of the 3Dprinter, and (iii) production speed is relatively low. Furthermore, the variety of materials used in 3D printing is also limited. On the other hand, new strategies are being developed that allow different types of materials to be used in the 3D printing technology [12–15]. Thanks to these novel technologies, many types of metal [16], plastic [17], composite [18], and organic materials [19] can be used in 3D printing. In biomedical applications, post-processing is of particular importance. For example, stair-stepped surface, which is a result of layer-by-layer manufacturing, may lead to undesirable surface conditions for implants required biocompatibility [20]. In such cases, surface finish operations should be done carefully and precisely. Moreover, clean and sterile manufacturing environments are required in the manufacture of medical products such as implants. In this context, precautions against contamination should be carefully taken for printing platform and other 3D printer equipment [21]. In this chapter, the general working principle of 3D printers, commonly used 3D printing technologies, and types of materials used in 3D printers were addressed. In addition, scientific studies focusing on 3D printing technology in the biomedical field have been discussed.