[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

羟氨苄青霉素引起大疱性类天疱疮样疹

Additive manufacturing (AM) is poised to bring about a revolution in the way products are designed, manufactured, and distributed to end users. This technology has gained significant academic as well as industry interest due to its ability to create complex geometries with customizable material properties. AM has also inspired the development of the maker movement by democratizing design and manufacturing. Due to the rapid proliferation of a wide variety of technologies associated with AM, there is a lack of a comprehensive set of design principles, manufacturing guidelines, and standardization of best practices. These challenges are compounded by the fact that advancements in multiple technologies (for example materials processing, topology optimization) generate a "positive feedback loop" effect in advancing AM. In order to advance research interest and investment in AM technologies, some fundamental questions and trends about the dependencies existing in these avenues need highlighting. The goal of our review paper is to organize this body of knowledge surrounding AM, and present current barriers, findings, and future trends significantly to the researchers. We also discuss fundamental attributes of AM processes, evolution of the AM industry, and the affordances enabled by the emergence of AM in a variety of areas such as geometry processing, material design, and education. We conclude our paper by pointing out future directions such as the "print-it-all" paradigm, that have the potential to re-imagine current research and spawn completely new avenues for exploration. The fundamental attributes and challenges/barriers of Additive Manufacturing (AM).The evolution of research on AM with a focus on engineering capabilities.The affordances enabled by AM such as geometry, material and tools design.The developments in industry, intellectual property, and education-related aspects.The important future trends of AM technologies.

The status, challenges, and future of additive manufacturing in engineering

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 (AM) technology has been researched and developed for more than 20 years. Rather than removing materials, AM processes make three-dimensional parts directly from CAD models by adding materials layer by layer, offering the beneficial ability to build parts with geometric and material complexities that could not be produced by subtractive manufacturing processes. Through intensive research over the past two decades, significant progress has been made in the development and commercialization of new and innovative AM processes, as well as numerous practical applications in aerospace, automotive, biomedical, energy and other fields. This paper reviews the main processes, materials and applications of the current AM technology and presents future research needs for this technology.

Additive manufacturing: technology, applications and research needs

Ceramic three dimensional parts have been fabricated by a Stereolithography (SL) process using a ceramic slurry containing alumina powder, UV curable monomer, diluent, photoinitiator and dispersant, subsequent removal of organic components and sintering. The SL process consists of fabricating parts with complex shapes layer by layer by laser polymerization of a ceramic/resin mixture. The effects of each component on the rheology of the ceramic suspension were investigated. Both, the addition of dispersant and diluent to the curable monomer and the increase in temperature decrease the viscosity down to suitable values for tape casting of the layers and for SL. The homogeneous and stable high ceramic concentration suspensions (53 vol%) exhibited a shear thinning behavior, which is favorable for casting the layers. Adequate cured depth (above 200 μm) and width were obtained even at high scanning speeds with an argon ionized laser.

Ceramic suspensions suitable for stereolithography

A cost-effective method of complex ceramic parts manufacturing using stereolithography has been developed. The process consists in fabricating ceramic pieces by laser polymerization of an UV curable monomeric system, subsequent removal of organic components and sintering. Highly concentrated suspensions of well dispersed ceramic particles (up to 60 vol%) in a reactive acrylic monomer, with a suitable rheological behaviour for the spreading of thin layers (down to 25 μm) were defined. Adequate cured depth (higher than 200 μm) is obtained even at high scanning speeds. Nevertheless, a compromise has to be found between the cured depth and the cured width to improve the dimensional resolution. The dimensional resolution reached on alumina partterns is about 200 μm with an energy density of 0.05 J · cm−2.

Stereolithography of structural complex ceramic parts

The processing of laminar ceramic composites from stacking of layers obtained by tape casting is described. In the case of composites for structural applications, the reinforcement mechanisms are briefly reviewed. It is shown that both strength and toughness can be improved. The evaluation of residual stresses allows a strategy for tailoring the mechanical properties of such composites to be developed. As an example, results are given in the case of laminar composites with layers made of alumina with various zirconia contents.

Laminar ceramic composites

Different investigations have been carried out to optimize an ink-jet printing technique, devoted to the fabrication of 3D fine scale ceramic parts, by adjustment of the fluid properties of the ceramic suspensions and by controlling the ejection and impact phenomena. A 10 vol.% PZT loaded suspension characterized by a Newtonian behavior corresponding to a viscosity of 10 mPa s and to a ratio Re / We 1/2 of 5.98 has been selected. The ejection and impact phenomena strongly depend on the driving parameters of the printing head, in particular the formation of the droplet, with satellite or not, as well as its velocity and volume are function of the pulse amplitude. Moreover, the conditions of ejection (droplet velocity and volume) control the characteristics of the deposit (definition, spreading and thickness uniformity). Green PZT pillar array corresponding to the skeleton of 1–3 ceramic polymer composite for imaging probes has been achieved by ink-jet printing with a definition equal to 90 μm.

3D fine scale ceramic components formed by ink-jet prototyping process

We report recent progress on fabrication of solid core microstructured fibers in chalcogenide glass. Several complex and regular holey fibers from Ga5Ge20Sb10S65 chalcogenide glass have been realized. We demonstrate that the “Stack & Draw“ procedure is a powerful tool against crystallisation when used with a very stable chalcogenide glass. For a 3 ring multimode Holey Fiber, we measure the mode field diameter of the fundamental mode and compare it successfully with calculations using the multipole method. We also investigate, via numerical simulations, the behaviour of fundamental mode guiding losses of microstructured fibers as a function of the matrix refractive index, and quantify the advantage obtained by using a high refractive index glass such as chalcogenide instead of low index glass.

/pdf/fabrication-of-complex-structures-of-holey-fibers-in-kaeptajjku.pdf

Thierry Chartier

Papers

Ceramic suspensions suitable for stereolithography

Stereolithography of structural complex ceramic parts

Laminar ceramic composites

3D fine scale ceramic components formed by ink-jet prototyping process

Fabrication of complex structures of Holey Fibers in Chalcogenide glass