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Emerging Technologies for Particle Engineering
Published in Dilip M. Parikh, Handbook of Pharmaceutical Granulation Technology, 2021
Various polymers have been investigated for 3D printing technologies, including fused deposition model, selective laser sintering, semi-solid extrusion, stereolithography, and inkjet printing. An excellent review by Ali et al. evaluated various polymers that can be used and their advantages and limitations. They describe different 3D printing models, namely, the fused deposition model and selective laser sintering (SLS). The fused deposition model is a two-step process where the main element is the melt extrusion at the processing temperatures that typically reach >100 °C. The extruded cooled filaments are then subjected to heating and melting during printing through a nozzle at much higher temperatures than used in extrusion [65]. Fina et al. investigated Kollidon® VA 64 and HPMC in SLS 3DP technology. By employing slow and faster laser scanning speeds, the authors fabricated the printlets with faster release characteristics [66]. Another 3D printing technology semi-solid extrusion (SSE) is used for sensitive APIs to avoid exposure to higher temperatures. This is a pressure-driven cold extrusion process requiring the use of a paste of drugs and excipients.
Dentin-Pulp Complex Regeneration
Published in Vincenzo Guarino, Marco Antonio Alvarez-Pérez, Current Advances in Oral and Craniofacial Tissue Engineering, 2020
Amaury Pozos-Guillén, Héctor Flores
Various techniques have been used to manufacture two- and three-dimensional scaffolds. The main technique to fabricate two-dimensional scaffolds is electrospinning; whereas the main techniques to fabricate three-dimensional scaffolds include solvent casting, freeze drying, particle/salt leaching, chemical/gas foaming, thermally induced phase separation and the foam-gel technique (Loh and Choong 2013; Lu et al. 2013; Park et al. 2015; Gomez-Lizarraga et al. 2017; Ortiz et al. 2017; Del Bakhshayesh et al. 2018; Granados-Hernandez et al. 2018; Vazquez-Vazquez et al. 2018; Xu et al. 2018). These techniques have some limitations to yield scaffolds with specific micro-architectures in terms of porosity, pore size, pore geometry and interconnectivity. They are still being used because of their low cost and minimal equipment complexity. Besides, due to their manufacturing conditions, these techniques do not allow including living cells or soluble factors within the process. Additive manufacturing techniques have arisen as a solution to these disadvantages. The most accepted of these techniques include: stereolithography, selective laser sintering, fused deposition modeling and three-dimensional printing (Moreno Madrid et al. 2019).
Enhanced Scaffold Fabrication Techniques for Optimal Characterization
Published in Naznin Sultana, Sanchita Bandyopadhyay-Ghosh, Chin Fhong Soon, Tissue Engineering Strategies for Organ Regeneration, 2020
Tshai Kim Yeow, Lim Siew Shee, Yong Leng Chuan, Chou Pui May
Selective laser sintering (SLS) applies powder bed fusion processes by using laser as an extreme heat source to sinter powder materials, Fig. 3.12. The powder will be melted and solidified layer-by-layer, eventually forming a 3D object. SLS printers are commonly equipped with two plates called pistons and a scanner system. In the beginning of the process, high power laser scans the first layer of powder that is laid onto the fabrication piston, selectively melting and sintering the powder material. Fabrication piston is moved lower after the first layer is solidified while the powder delivery bed is raised slightly to allow a roller to swipe another layer of powder on top of the previous solidified layer. This procedure is repeated to allow the laser to melt and solidify polymeric powder layer-by-layer, until the designed part has been finished bottom to top (Mazzoli 2013).
Selective laser sintering 3D printing – an overview of the technology and pharmaceutical applications
Published in Drug Development and Industrial Pharmacy, 2020
Naseem A. Charoo, Sogra F. Barakh Ali, Eman M. Mohamed, Mathew A. Kuttolamadom, Tanil Ozkan, Mansoor A. Khan, Ziyaur Rahman
Various 3DP technologies have been reported in the literature for manufacturing pharmaceuticals including selective laser sintering (SLS). SLS was invented by Carl Deckard and Joe Beaman in early 1980. Most common applications of this technology are printing metal parts, implants, and tissue scaffolds [5–7]. The technology offers many advantages over other methods of 3DP for pharmaceuticals’ printing. The printing is solvent-free with relatively high speed compared to other methods, and no requirement of filament form of raw material, polymerizable monomer/polymer liquid binder, and post processing. Solvent-free nature makes it ideal to fabricate water and organic solvent sensitive drug molecules. Furthermore, printlets are immediately available after printing for dispensing and consumption since there are no post-processing steps such as drying or curing except harvesting printlets from the loose powder. Printlets containing multiple drugs with different release and mechanical characteristics can also be fabricated by manipulating process and material attributes [8,9]. The only prerequisite of the method is thermoplastic and thermal stability of formulation components [10]. Only FDA–approved thermoplastic excipients and polymers, which are currently being used in hot-melt extrusion (HME) process, can be used in the SLS process. Other challenges in the SLS, which are also applicable to other 3DP methods, are recycling/reuse of materials, in-process testing/monitoring, and finding good manufacturing practice (GMP) compliant printer [4]. This article reviews the SLS technology, technical and regulatory challenges.
Numerical and experimental evaluation of TPMS Gyroid scaffolds for bone tissue engineering
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
A. P. G. Castro, R. B. Ruben, S. B. Gonçalves, J. Pinheiro, J. M. Guedes, P. R. Fernandes
As important as the development methods and target applications, scaffolds shall be produced with enough accuracy. This means that the designed structure shall correspond to the fabricated one, in order to promote the adequate cellular and tissue response after implantation (Castro & Lacroix 2018). 3D printing, electrospinning or selective laser sintering have been applied in scaffold manufacturing (Eshraghi & Das 2012; Lu et al. 2013; Wismer et al. 2014; Hollister et al. 2016). In the past, it has been found that produced scaffolds were different from the respective project and this raised concerns about the applicability of these devices in the biomedical industry (Hollister & Murphy 2011; Campos Marin & Lacroix 2015; Webber et al. 2015). 3D MultiJet printing, which is an additive manufacturing technique, has proven to be a good option for scaffold manufacture, benefiting from efficient cost control and high production accuracy (Castilho et al. 2011; Velasco et al. 2016).
3‐D printed spectacles: potential, challenges and the future
Published in Clinical and Experimental Optometry, 2020
Ling Lee, Anthea M Burnett, James G Panos, Prakash Paudel, Drew Keys, Harris M Ansari, Mitasha Yu
Selective laser sintering is the most commonly used powder bed fusion technique that prints with amorphous and semi‐crystalline polymers. Polycarbonate is a readily used material for spectacle lenses and safety goggles due to attributes such as high impact resistance.1997 Polycarbonate is also an available amorphous polymer powder for selective laser sintering. However, when lower laser energy densities are applied to the powder, mechanical strength is lost, while higher energy densities result in material degradation.2003 Thus, selective laser sintering printing of polycarbonate has been considered unsuitable for functional components without post‐processing.2007