# Additive Manufacturing Interventions during the COVID-19 Pandemic: South Africa
## 2 Additive Manufacturing (3D Printing)  
Additive manufacturing (AM) or 3D printing could be described as the process of joining materials together layer-by-layer based on information from a computer-aided design (CAD) model to produce 3D structures [19]. CAD models are generated by a computerized system, and based on the information on the CAD, a 3D object is produced. The American Society for Testing and Materials (ASTM) international committee F42 on AM technologies [20] classified AM technologies into seven categories: material jetting, binder jetting, sheet lamination, powder bed fusion, directed energy deposition, photopolymer vat and material extrusion. Each of the AM technologies works by the superposition of single layers, which results in the production of the 3D object, as prescribed by the CAD model [21]. The layer-by-layer manufacturing process of AM technologies enables the production of 3D structures with complex geometries (e.g., back tapers, intricate cooling channels, customized porous structures, and special lattices or hollow structures) which enhances the technical, geometrical, and functional properties of the 3D-printed objects [22]. The 3D structures can be rapidly optimized and monolithically produced, as opposed to the multiple assembly steps of conventional methods of manufacturing (milling,forging, sheet forming, perforated/slotted, sheet folding, extrusion, investment casting, grinding, etc.) [11]. The monolithic process of manufacturing near-net shapes layer-by-layer would translate into a reduction in manufacturing time, reduction in waste production during manufacturing (green manufacturing), reduction in assembling and maintenance cost, weight reduction, and improvement in reliability and efficiency [19]. The layer-by-layer manufacturing approach has ushered in the manufacturing of 3D objects with multiple materials for specific applications [23]. The possibility of using different materials during the AM process has led to the production of parts with the desired properties in strategic locations [24]. This is an evolutional paradigm shift from the traditional methods of fabrications, which is termed \"industrial revolution\" [25]. This industrial revolution capacity of additive manufacturing could enable the manufacturing of 3D objects with defined varied mechanical properties in specific geometrical locations of the manufactured objects [26], such as: thermal conductivity in conformal cooling channels, thermal barrier coatings, optical properties in laser telecommunication systems, high hardness, high-temperature-resistant properties in turbine engines, dielectric and magnetic properties in antenna and meta-materials; the inclusion of embedded components such as resistors and sensors in electrical devices; and increasing the lifetime and efficiency of tools in abrasive wear environment [27]. Using the versatility of AM technology to manufacture such products in one manufacturing cycle provides a window of possibility for manufacturing hospital equipment and PPE with customized features that could aid in preventing the spread of COVID-19. It is therefore not surprising that since the outbreak of COVID-19, scholars [14; 26; 28; 29] in the field of additive manufacturing have touted that the layer-wise manufacturing process of AM technology could be used to prevent the spread of COVID-19 by incorporating antimicrobial agents such as Cu and Ag into 3D-manufactured object surfaces. Additively manufactured objects with such antimicrobial agents will kill microorganisms on contact, which will certainly prevent the spread of the disease. Using the layer-wise manufacturing strategy to manufacture hospital equipment with embedded antimicrobial agents (Cu, Ag, etc.) would enable hospital equipment and PPE to kill microorganisms upon contact with its surface and PPE.