Lithography-based addtive manufacture of ceramic biodevices with design-controlled surface topographies

The possibility of manufacturing textured materials and devices, with surface properties controlled from the design stage, instead of being the result of machining processes or chemical attacks, is a key factor for the incorporation of advanced functionalities to a wide set of micro- and nanosystems. High-precision additive manufacturing (AM) technologies based on photopolymerization, together with the use of fractal models linked to computer-aided design tools, allow for a precise definition of final surface properties. However, the polymeric master parts obtained with most commercial systems are usually inadequate for biomedical purposes and their limited strength and size prevents many potential applications. On the other hand, additive manufacturing technologies aimed at the production of final parts, normally based on layer-by-layer melting or sintering ceramic or metallic powders, do not always provide the required precision for obtaining controlled micro-structured surfaces with high-aspect-ratio details. Towards the desired degree of precision and performance, lithography-based ceramic manufacture is a remarkable option, as we discuss in the present study, which presents the development of two different micro-textured biodevices for cell culture. Results show a remarkable control of the surface topography of ceramic parts and the possibility of obtaining design-controlled micro-structured surfaces with high-aspect-ratio micro-metric details

Specific CT 3D rendering of the treatment zone after Irreversible Electroporation (IRE) in a pig liver model: the “Chebyshev Center Concept” to define the maximum treatable tumor size

Background: Size and shape of the treatment zone after Irreversible electroporation (IRE) can be difficult to depict due to the use of multiple applicators with complex spatial configuration. Exact geometrical definition of the treatment zone, however, is mandatory for acute treatment control since incomplete tumor coverage results in limited oncological outcome. In this study, the “Chebyshev Center Concept” was introduced for CT 3d rendering to assess size and position of the maximum treatable tumor at a specific safety margin. Methods: In seven pig livers, three different IRE protocols were applied to create treatment zones of different size and shape: Protocol 1 (n = 5 IREs), Protocol 2 (n = 5 IREs), and Protocol 3 (n = 5 IREs). Contrast-enhanced CT was used to assess the treatment zones. Technique A consisted of a semi-automated software prototype for CT 3d rendering with the “Chebyshev Center Concept” implemented (the “Chebyshev Center” is the center of the largest inscribed sphere within the treatment zone) with automated definition of parameters for size, shape and position. Technique B consisted of standard CT 3d analysis with manual definition of the same parameters but position. Results: For Protocol 1 and 2, short diameter of the treatment zone and diameter of the largest inscribed sphere within the treatment zone were not significantly different between Technique A and B. For Protocol 3, short diameter of the treatment zone and diameter of the largest inscribed sphere within the treatment zone were significantly smaller for Technique A compared with Technique B (41.1 ± 13.1 mm versus 53.8 ± 1.1 mm and 39.0 ± 8.4 mm versus 53.8 ± 1.1 mm; p < 0.05 and p < 0.01). For Protocol 1, 2 and 3, sphericity of the treatment zone was significantly larger for Technique A compared with B. Conclusions: Regarding size and shape of the treatment zone after IRE, CT 3d rendering with the “Chebyshev Center Concept” implemented provides significantly different results compared with standard CT 3d analysis. Since the latter overestimates the size of the treatment zone, the “Chebyshev Center Concept” could be used for a more objective acute treatment control

Additive Fertigung in der digitalen Zahnheilkunde

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New Materials for Rapid Prototyping Applications Highlight

Why Do We Need New RP Materials? Rapid prototyping (RP) has become a widely used tool for the fabrication and evaluation of physical prototypes during the product development cycle. RP is used since it can produce prototypes with arbitrary shapes quickly and at a lower cost than traditional prototyping techniques. Recently RP has also been investigated regarding its ability to replace traditional mass manufacturing processes in applications where only one or a small number of individually shaped parts is required. Recently, Mühlhaupt and coworkers Regarding the type of applications for which the RP models are used, the following groups of prototypes can be distinguished: iii) Visual aids, which serve for visualizing design concepts and evaluate the ergonomics of a prototype. iii) Concept models that provide a certain functionality and are accurate enough to test whether individual parts fit properly within an assembly. iii) Master patterns for tooling and molding processes. iv) Functional parts that can be used to evaluate the functionality of certain parts before they are mass fabricated. Functional models need to fulfill high requirements regarding material quality and shape accuracy. iv) Customized products, which are tailored according to specific requirements of the customer. Customized products are usually made in quantities between one and ten. Applications are mostly in the field of biomedicine, where individual shapes according to a patient's requirements have to be manufactured. The field of visual aids, concept models, and master patterns is traditionally the 'home-ground' of RPs. Most RP processes are optimized for fabricating such prototypes. Since the market for classical prototyping services is saturated and prices for parts offered by RP service bureaus have fallen constantly

The Role of Solvents in Lithography-Based Ceramic Manufacturing of Lithium Disilicate

Digital dentistry is increasingly replacing conventional methods of manually producing dental restorations. With regards to computer-aided manufacturing (CAM), milling is state of the art. Additive manufacturing (AM), as a complementary approach, has also found its way into dental practices and laboratories. Vat photo-polymerization is gaining increasing attention, because it enables the production of full ceramic restorations with high precision. One of the two predominantly used ceramic materials for these applications is lithium disilicate, Li2Si2O5. This glass ceramic exhibits a substantial fracture toughness, although possesses much lower bending strength, than the other predominantly used ceramic material, zirconia. Additionally, it shows a much more natural optical appearance, due to its inherent translucency, and therefore is considered for anterior tooth restorations. In this work, an optimized formulation for photo-reactive lithium disilicate suspensions, to be processed by vat photo-polymerization, is presented. Following the fundamental theoretical considerations regarding this processing technique, a variety of solvents was used to adjust the main properties of the suspension. It is shown that this solvent approach is a useful tool to effectively optimize a suspension with regards to refractive index, rheology, and debinding behavior. Additionally, by examining the effect of the absorber, the exposure time could be reduced by a factor of ten

Visible Light Photoinitiator for 3D-Printing of Tough Methacrylate Resins

Lithography-based additive manufacturing was introduced in the 1980s, and is still the method of choice for printing accurate plastic parts with high surface quality. Recent progress in this field has made tough photopolymer resins and cheap LED light engines available. This study presents the influence of photoinitiator selection and post-processing on the thermomechanical properties of various tough photopolymers. The influence of three photoinitiators (Ivocerin, BAPO, and TPO-L) on the double-bond conversion and mechanical properties was investigated by mid infrared spectroscopy, dynamic mechanical analysis and tensile tests. It was found that 1.18 wt % TPO-L would provide the best overall results in terms of double-bond conversion and mechanical properties. A correlation between double-bond conversion, yield strength, and glass transition temperature was found. Elongation at break remained high after post-curing at about 80–100%, and was not influenced by higher photoinitiator concentration. Finally, functional parts with 41 MPa tensile strength, 82% elongation at break, and 112 °C glass transition temperature were printed on a 405 nm DLP (digital light processing) printer

AM’s industrial impact celebrated as Sweden hosts ASMET’s fourth Metal Additive Manufacturing Conference

The fourth Metal Additive Manufacturing Conference (MAMC 2019), organised by the Austrian Society for Metallurgy and Materials (ASMET), took place in Örebro, Sweden, from November 25–27, 2019. The event, which attracted an international audience, covered a broad range of metal AM technologies and considered the technical challenges that need to be overcome to make the industry more economically competitive with conventional manufacturing. Prof Dr Jürgen Stampfl, Prof Nader Asnafi, Dr Bruno Hribernik, and Dr Gerhard Hackl review the event for Metal AM magazine

Analysis of the mechanical anisotropy of stereolithographic 3D printed polymer composites

3D printing is a manufacturing technique based on the structuring of parts layer by layer. This principle yields a specific printing direction, that is the spatial orientation of the produced layers. Thus, potential anisotropy arising from the printing direction is a major concern in 3D printing. The mechanical properties of a biocompatible resin mainly consisting of methacrylates and tricalcium phosphate particles is examined. Various tests are conducted to examine the mechanical anisotropy of testing samples manufactured with a 3D printer based on stereolithography. A digital light processing unit (λ = 375 nm) is utilized to produce test samples in three orthogonal directions. Bending behaviour, fracture toughness, and hardness are measured. Furthermore, light microscopy is utilized to assess the properties of the fractured samples qualitatively. Assessed values are in agreement with comparable materials and show no statistically significant (p = 0.095) evidence of anisotropic behaviour. Sample orientation has no impact on the mechanical properties of the produced parts. Thus, production time and capabilities can be optimized by varying and combining sample orientation without changing the mechanical performance of the engineered parts significantly

AM’s industrial impact celebrated as Sweden hosts ASMET’s fourth Metal Additive Manufacturing Conference

The fourth Metal Additive Manufacturing Conference (MAMC 2019), organised by the Austrian Society for Metallurgy and Materials (ASMET), took place in Örebro, Sweden, from November 25–27, 2019. The event, which attracted an international audience, covered a broad range of metal AM technologies and considered the technical challenges that need to be overcome to make the industry more economically competitive with conventional manufacturing. Prof Dr Jürgen Stampfl, Prof Nader Asnafi, Dr Bruno Hribernik, and Dr Gerhard Hackl review the event for Metal AM magazine