The interest in nanoscale materials stems from the fact that new properties are acquired at this length scale and, equally important, that these properties * To whom correspondence should be addressed. Phone, 404-8940292; fax, 404-894-0294; e-mail, mostafa.el-sayed@ chemistry.gatech.edu. † Case Western Reserve UniversitysMillis 2258. ‡ Phone, 216-368-5918; fax, 216-368-3006; e-mail, burda@case.edu. § Georgia Institute of Technology. 1025 Chem. Rev. 2005, 105, 1025−1102

Chemistry and properties of nanocrystals of different shapes.

Scaffolds in tissue engineering bone and cartilage.

The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

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

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

A novel process is discussed for producing a wide variety of ceramic powders with unique physical and chemical characteristics. Silicon, Si3N4, and SiC powders were produced from CO2 laser-heated gas-phase reactants; a detailed description of this laser-driven process is presented. The physical, chemical, and crystalline nature of the resultant powders and the effect of process variables are discussed in Part II. In this process, reactant gases are rapidly heated by CO2 laser radiation and decompose, causing particles to nucleate and grow rapidly. Analytical models of fluid flow, heat transfer, heating rates, and powder-formation mechanisms are discussed. The powders produced in this process are very fine (<0.1μm), spherical, nearly monodispersed in size, extremely pure, and loosely agglomerated.

Sinterable Ceramic Powders from Laser-Driven Reactions: I, Process Description and Modeling

Commercial solid freeform fabrication (SFF) systems, which have been developed for fabrication of wax and polymer parts for form and fit and secondary applications, such as moulds for casting, etc., require further improvements for use in direct processing of structural ceramic and metal parts. Defects, both surface as well as internal, are undesirable in SFF processed ceramic and metal parts for structural and functional applications. Process improvements are needed before any SFF technique can successfully be commercialized for structural ceramic and metal processing. Describes process improvements made in new SFF techniques, called fused deposition of ceramics (FDC) and metals (FDMet), for fabrication of structural and functional ceramic and metal parts. They are based on an existing SFF technique, fused deposition modelling (FDM) and use commercial FDM systems. The current state of SFF technology and commercial FDM systems results in parts with several surface and internal defects which, if not eliminated, severely limit the structural properties of ceramic and metal parts thus produced. Describes systematically, in detail, the nature of these defects and their origins. Discusses several novel strategies for elimination of most of these defects. Shows how some of these strategies have successfully been implemented to result in ceramic parts with structural properties comparable to those obtained in conventionally processed ceramics.

Structural quality of parts processed by fused deposition

A fused deposition process is used to form three-dimensional solid objects from a mixture including a particulate composition dispersed in a binder. The article is formed by depositing the mixture in repeated layers of predefined thickness, with each layer solidifying before the next adjacent layer is dispensed. Following formation and a binder removal step, the article may be at least partially densified to achieve preselected properties. The process permits three-dimensional articles to be formed relatively quickly and inexpensively, without the need for molds or other tooling.

Solid freeform fabrication methods

Si, Si3N4, and SiC powders which possess a unique set of characteristics were produced by a laser-driven gas-phase synthesis process. The powders have a fine particle size (<0.1 μm), are spherical, have a narrow range of particle sizes, are free of hard agglomerates, have a high degree of phase purity, and have a high absolute purity (<0.1% including oxygen). A detailed analysis of the physical, chemical, and crystalline characteristics of Si and Si3N4 is presented. A brief discussion of our initial work with SiC is also included. The dependence of particle characteristics on the various process parameters (laser power, cell pressure, gas composition) is discussed and related to a model of the powder-synthesis process.

Sinterable Ceramic Powders from Laser‐Driven Reactions: II, Powder Characteristics and Process Variables

In this article we present the system that we have developed at Rutgers University for the solid freeform fabrication of multiple ceramic actuators and sensors. With solid free form fabrication, a part is built layer by layer, with each layer composed of roads of material forming the boundary and the interior of the layer. With our system, up to four different types of materials can be deposited in a given layer with any geometry. This system is intended for fabrication of functional parts; therefore the accuracy and precision of the fabrication process are of extreme importance.

Stephen C. Danforth

Papers

Sinterable Ceramic Powders from Laser-Driven Reactions: I, Process Description and Modeling

Structural quality of parts processed by fused deposition

Solid freeform fabrication methods

Sinterable Ceramic Powders from Laser‐Driven Reactions: II, Powder Characteristics and Process Variables

A novel system for fused deposition of advanced multiple ceramics