3D printing and nanotechnology

Introduction to additive manufacturing technologies and rapid prototyping

The rapid prototyping has dramatically expanded over the last 20 yrs, with the two-dimensional (2D) and three-dimensional (3D) printing processes to be in the forefront and the most promising technologies among others. ^, 2D and 3D printing are additive manufacturing (AM) processes based on sequential addition of (nano-)material layers offering the opportunity to print either 2D parts (thin or thick films/layers as self-standing films or coatings) or bulk 3D parts and components made of different (nano-)materials with variable mechanical and physical properties. ^, Namely, the global sales in 3D printing (products and services) rose by 21% from the market in 2017 ( https://www.forbes.com ) reaching 7 B$, while the total AM market only for the automotive sector is expected to grow from 1.5 B€ in 2018 to 5.3 B€ in 2023 and 12.6 B€ in 2028 ( https://www.smartechpublishing.com/news/smartec-report-automotive-additive-manufacturing-market/ ).

Roll-to-roll and sheet-to-sheet 2D AM

The 2D AM processing could be a continuous process otherwise defined as roll-to-roll (R2R) or sheet-to-sheet (S2S), both of which allow a continuous deposition of materials as inks/pastes, melts, etc., onto rigid or flexible substrates (glass, plastic, metallic foils, textiles, etc.). In a R2R process, the materials are deposited in motion between two moving rolls named as unwinder and winder. R2R is an important class of substrate-based manufacturing processes in which additive and subtractive processes (e.g., laser scribing) can be used to build components in a continuous manner. R2R is a process that combines many technologies to produce rolls of finished material in an efficient and cost-effective manner with the benefits of high production rates of mass quantities. High throughput and low cost are the factors that differentiate R2R manufacturing from conventional manufacturing, which is slower and more expensive due to the multiple steps involved. Today, roll to roll (R2R) processing is applied in numerous manufacturing fields such as (i) coating of textiles (e.g., using a bath coating technology otherwise known as dyeing process), (ii) prepregs for advanced carbon fiber–reinforced polymer structural composites (bath or slot-die deposition of epoxy onto fabrics), and (iii) packaging, i.e., smart packaging (e.g., slot-die, gravure, bath coating, screen printing, flexography of inks, varnishes), flexible and large area printed electronics (e.g., slot-die, gravure, bath coating, screen printing, flexography, inkjet printing of electronic inks and pastes), thin-film batteries and (bio-)electrodes (e.g., slot-die, screen printing), textiles for wearables (e.g., inkjet printing, screen printing, and flexography), membranes (e.g., slot-die), etc. The global R2R technology market is expected to reach 35.69 B$ in 2023, expanding at a compound annual growth rate of 13.5% from 2015 to 2023 ( http://www.mobilecomputingtoday.co.uk/4572/global-roll-roll-r2r-technology ).

Fig. 2.1 demonstrates (A) a schematic of a R2R AM process, as well as (B) a representative R2R printing/coating line produced by FOM company (FOM Technologies, Denmark); while in (C), a schematic of a S2S printing coating AM process is depicted, and in (D), a S2S printing slot-die and blade coating machine produced by Coatema printing technologies company (Coatema Coating Machinery GmbH, Germany) is depicted.

3D AM

3D printing is an AM process based on sequential addition of material layers offering the opportunity to print 3D parts and components made of different materials with variable mechanical and physical properties. The first 3D print was reported by Hideo Kodama in 1982. Since then, 3D printers have become much more accessible and are now able to print with a multitude of materials including metals, wood products, and thermoplastics such as polylactic acid (PLA) and others. In addition, there are various techniques for printing solid materials in 3D, including as shown in Fig. 2.2A : inkjet 3D printing, Fig. 2.2B : fused deposition modeling (FDM), Fig. 2.2C : stereolithography, and Fig. 2.2D : selective laser sintering, electron-beam freeform fabrication, and direct metal laser sintering, among others.

Fig. 2.3 demonstrates (A) the flowchart of a 3D printing AM process including the generation of the computer-aided design (CAD) model (in a CAD-specific software, e.g., SOLIDWORKS, AutoCAD, 3D Builder) toward exporting it to an stl. file capable of being communicated with most of the 3D printer software for further the printing process (printing process has to be simulated, process parameters to be chosen, etc., from the printer software) ( http://reprap.org/wiki/CAM_Toolchains ). In Fig. (B), a CAD model of a surgery retractor is depicted, as well as a 3D FDM printer for thermoplastic materials (MakerBot Inc., USA) used to print the objects is shown on the right-hand side of the image.