Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting....

Polymers for 3D Printing and Customized Additive Manufacturing

https://pure.hw.ac.uk/ws/files/10766137/Melchels2010_Biomaterials_31_24_6121.pdf

A review on stereolithography and its applications in biomedical engineering

Additive manufacturing: scientific and technological challenges, market uptake and opportunities

Laser sintering of polyamides and other polymers

The field of 3D printing is continuing its rapid development in both academic and industrial research environments. The development of 3D printing technologies has opened new implementations in rapid prototyping, tooling, dentistry, microfluidics, biomedical devices, tissue engineering, drug delivery, etc. Among different 3D printing techniques, photopolymerization-based process (such as stereolithography and digital light processing) offers flexibility over the final properties of the 3D printed materials (such as optical, chemical, and mechanical properties) using versatile polymer chemistry. The strategy behind the 3D photopolymerization is based on using monomers/oligomers in liquid state (in the presence of photoinitiators) that can be photopolymerized (via radical or cationic mechanism) upon exposure to light source of different wavelengths (depending on the photoinitiator system). An overview of recent evolutions in the field of photopolymerization-based 3D printing and highlights of novel 3D print...

Photopolymerization in 3D Printing

Additive processing technologies are rapidly growing in all fields of application. A large number of scientific publications were investigated in order to provide a comprehensive overview of rapid prototyping methods for polymers and their applications, of currently available materials and research concerning additive processes. The current problems of additive processes are described, together with their potential solutions. Furthermore, this article delivers an insight into possible future trends of additive technologies.

Additive Processing of Polymers

Purpose – Fused deposition modeling (FDM) is a layer by layer technology with the potential to create complex and individual parts from thermoplastic materials such as ABS. The use of Polylactic acid (PLA) and tricalcium phosphate (TCP) as resorbable composite is state of the art in tissue engineering and maxillofacial surgery. The purpose of this paper is to evaluate the processing conditions and the performance of parts (e.g. mechanical properties) manufactured with a FDM machine.Design/methodology/approach – In this paper, the general suitability of PLA for the processing with FDM is evaluated and material specific effects (e.g. crystallization and shrinkage) are shown. Therefore, the characterization of the semi‐crystalline biodegradable material by thermal, mechanical and microscopic analysis is carried out.Findings – Facts, which affect the functional properties of the samples, are analyzed. Among them, the processing temperature and sample size significantly affect the morphology of the final compo...

Suitability of PLA/TCP for fused deposition modeling

Development of a characterization approach for the sintering behavior of new thermoplastics for selective laser sintering

With additive manufacturing (AM) individual and biocompatible implants can be generated by using suitable materials. The aim of this study was to investigate the biological effects of polylactic acid (PLA) manufactured by Fused Deposition Modeling (FDM) on osteoblasts in vitro according to European Norm / International Organization for Standardization 10,993–5. Human osteoblasts (hFOB 1.19) were seeded onto PLA samples produced by FDM and investigated for cell viability by fluorescence staining after 24 h. Cell proliferation was measured after 1, 3, 7 and 10 days by cell-counting and cell morphology was evaluated by scanning electron microscopy. For control, we used titanium samples and polystyrene (PS). Cell viability showed higher viability on PLA (95,3% ± 2.1%) than in control (91,7% ±2,7%). Cell proliferation was highest in the control group (polystyrene) and higher on PLA samples compared to the titanium samples. Scanning electron microscopy revealed homogenous covering of sample surface with regularly spread cells on PLA as well as on titanium. The manufacturing of PLA discs from polylactic acid using FDM was successful. The in vitro investigation with human fetal osteoblasts showed no cytotoxic effects. Furthermore, FDM does not seem to alter biocompatibility of PLA. Nonetheless osteoblasts showed reduced growth on PLA compared to the polystyrene control within the cell experiments. This could be attributed to surface roughness and possible release of residual monomers. Those influences could be investigated in further studies and thus lead to improvement in the additive manufacturing process. In addition, further research focused on the effect of PLA on bone growth should follow. In summary, PLA processed in Fused Deposition Modelling seems to be an attractive material and method for reconstructive surgery because of their biocompatibility and the possibility to produce individually shaped scaffolds.

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In-vitro evaluation of Polylactic acid (PLA) manufactured by fused deposition modeling.

A shaped body comprised of individual, interconnected layers may be produced from fibers in accordance with a solid freeform fabrication or rapid prototyping method. The fibers may be produced by extrusion molding a thermoplastic material.

Dominik Rietzel

Papers

Additive Processing of Polymers

Suitability of PLA/TCP for fused deposition modeling

Development of a characterization approach for the sintering behavior of new thermoplastics for selective laser sintering

In-vitro evaluation of Polylactic acid (PLA) manufactured by fused deposition modeling.

Fibers and methods for use in solid freeform fabrication