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This chapter introduces four types of advanced reconfigurable leaky‐wave antenna (LWA) structures for fixed‐frequency beam scanning, i.e., a reconfigurable Fabry–Perot LWA, a period‐reconfigurable substrate‐integrated‐waveguide LWA, a reconfigurable composite right‐/left‐handed LWA, and a uniplanar two‐dimensional multi‐beam LWA suited for millimeter‐wave operations. These antenna configurations and their operating mechanisms and performance are described. A way to produce a full‐range scanning LWA is through the introduction of metamaterial constructs, i.e., artificial materials with exotic properties that can be tailored to a given application. The two‐dimensional multi‐beam antenna presented divides the problem of generating 2‐D multi‐beams into two independent, one‐dimensional beamforming pieces. This topology makes it possible to have a flat uniplanar structure. Some future directions of research in reconfigurable LWAs are discussed to conclude the chapter.

Fluorescent materials can shift energy between wavelengths, thereby creating bright and saturated colors both in natural and artificial materials. However, rendering fluorescence for continuous wavelengths or combined with wavelength dependent path configurations so far has only been feasible using spectral unidirectional methods. We present a regularization-based approach for supporting fluorescence in a spectral bidirectional path tracer. Our algorithm samples camera and light sub-paths with independent wavelengths, and when connecting them mollifies the BSDF at one of the connecting vertices such that it reradiates light across multiple wavelengths. We discuss arising issues such as color bias in early iterations, consistency of the method and MIS weights in the presence of spectral mollification. We demonstrate our method in scenes combining fluorescence and transport phenomena that are difficult to render with unidirectional or spectrally discrete methods.

Objective: This review integrates published scientific information about the fluorescence of natural teeth, dental resins and ceramics, and the main methods of analysis and quantification presented in the literature. Overview: Fluorescence is an emission of light (photons) by a substance that has absorbed light of higher energy. In natural teeth, it is more intense in the dentin than in the enamel and presents a bluish-white color. In dental resins and ceramics, fluorescence is obtained by the incorporation of materials that contain rare-earth luminescence centers (more precisely lanthanide luminescence centers), which allows these artificial materials to simulate natural teeth in a more beautiful and vital-looking way. However, the lack of knowledge about this optical phenomenon on the part of professionals indicates the need for more scientific studies and dissemination on this topic. Conclusions: Aesthetic materials have variable spectral compositions and fluorescence intensities, which are not always compatible with natural teeth. The fluorescence of teeth and restorative materials can be influenced by several factors, such as aging, temperature, and bleaching. Several devices for fluorescence evaluation and quantification are used in studies under different methodologies, but the small number of studies on the subject make it difficult to compare their results. Clinical Significance: Fluorescence is a fundamental optical property for aesthetic rehabilitations since its presence and intensity in the restorative materials allows achieving an aesthetic result much closer to reality. However, the fluorescent behavior of natural teeth and aesthetic restorative materials is not yet fully understood by researchers and clinicians. Greater understanding of this phenomenon will contribute to the selection, indication, and clinical use of these materials., CAPES (Coordination for the Improvement of Higher Education Personnel), Brazil, Grant/Award Number: 88881.119044/2016-01 and FCT (Foundation for Science and Technology), Portugal, Grant/Award Number: NORTE 01-0145-FEDER-000018, POCI-01-0145-FEDER-006941, UID/EEA/04436/2013.

Reciprocal space engineering allows tailoring the scattering response of media with a low refractive-index contrast. Here it is shown that a quasiperiodic leveled-wave structure with well-defined reciprocal space and random real space distribution can be engineered to open a complete photonic bandgap (CPBG) for any refractive-index contrast. For these structures, an analytical estimation is derived, which predicts that there is an optimal number of Bragg peaks for any refractive-index contrast. A finite 2D or 3D CPBG is expected at this optimal number even for an arbitrarily small refractive-index contrast. Results of numerical simulations of dipole emission in 2D and 3D structures support the estimations. In 3D simulations, an emission suppression of almost 10 dB is demonstrated with a refractive index down to 1.38. The 3D structures are realized by additive manufacturing on millimeter scale for a material with a refractive index of n ≈ 1.59. Measurements confirm a strong suppression of microwave transmission in the expected frequency range.

Proteinaceous materials based on the amyloid core structure have recently been discovered at the origin of biological functionality in a remarkably diverse set of roles, and attention is increasingly turning towards such structures as the basis of artificial self-assembling materials. These roles contrast markedly with the original picture of amyloid fibrils as inherently pathological structures. Here we outline the salient features of this class of functional materials, both in the context of the functional roles that have been revealed for amyloid fibrils in nature, as well as in relation to their potential as artificial materials. We discuss how amyloid materials exemplify the emergence of function from protein self-assembly at multiple length scales. We focus on the connections between mesoscale structure and material function, and demonstrate how the natural examples of functional amyloids illuminate the potential applications for future artificial protein based materials.

Assembling different kinds of 2D nanosheets into heterostructures presents a promising way of designing novel artificial materials with new and improved functionalities by combining the unique properties of each component. In the past few years, black phosphorus nanosheets (BPNSs) have been recognized as a highly feasible 2D material with outstanding electronic properties, a tunable bandgap, and strong in-plane anisotropy, highlighting their suitability as a material for constructing heterostructures. In this study, recent progress in the construction of BPNS-based heterostructures ranging from 2D hybrid structures to 3D networks is discussed, emphasizing the different types of interactions (covalent or noncovalent) between individual layers. The preparation methods, optical and electronic properties, and various applications of these heterostructures-including electronic and optoelectronic devices, energy storage devices, photocatalysis and electrocatalysis, and biological applications-are discussed. Finally, critical challenges and prospective research aspects in BPNS-based heterostructures are also highlighted.

The transformation of recognition signals into regulating macroscopic behaviors of biological entities (e.g., biomolecules and cells) is an extraordinarily challenging task in engineering interfacial properties of artificial materials. Recently, there has been extensive research for dynamic biointerfaces driven by biomimetic techniques. Weak interactions and chirality are two crucial routes that nature uses to achieve its functions, including protein folding, the DNA double helix, phospholipid membranes, photosystems, and shell and tooth growths. Learning from nature inspires us to design dynamic biointerfaces, which usually take advantage of highly selective weak interactions (e.g., synergetic chiral H-bonding interactions) to tailor their molecular assemblies on external stimuli. Biomolecules can induce the conformational transitions of dynamic biointerfaces, then drive a switching of surface characteristics (topographic structure, wettability, etc.), and eventually achieve macroscopic functions. The emerging progresses of dynamic biointerfaces are reviewed and its role from molecular recognitions to biological functions highlighted. Finally, a discussion is presented of the integration of dynamic biointerfaces with the basic biochemical processes, possibly solving the big challenges in life science.

Van der Waals heterostructures designed by assembling isolated two-dimensional (2D) crystals have emerged as a new class of artificial materials with interesting and unusual physical properties. Here, the multilayer MoS2–WS2 heterostructures with different configurations are reported and their optoelectronic properties are studied. It is shown that the new heterostructured material possesses new functionalities and superior electrical and optoelectronic properties that far exceed the one for their constituents, MoS2 or WS2. The vertical transistor exhibits a novel rectifying and bipolar behavior, and can also act as photovoltaic cell and self-driven photodetector with photo-switching ratio exceeding 103. The planar device also exhibits high field-effect ON/OFF ratio (>105), high electron mobility of 65 cm2/Vs, and high photo­responsivity of 1.42 A/W compared to that in isolated multilayer MoS2 or WS2 nanoflake transistors. The results suggest that formation of MoS2–WS2 heterostructures could significantly enhance the performance of optoelectronic devices, thus open up possibilities for future nanoelectronic, photovoltaic, and optoelectronic applications.

Realizing new functions through the construction of ordered structures not only exists naturally in nature, but also in artificial materials. However, much research focuses more on the relationship between structure and performance rather than on the impact of functional units themselves. Reviewing previous research findings, a "paradigm" of material research is proposed, which is based on ordered structures with functional units (OSFU) such as compositions, phases, domains, and twins. The goal is to draw more intensive attention of researchers to this concept and thus to promote the development of this field toward a deeper and broader direction, producing highly influential research results.

Rationally designed artificial materials, called metamaterials, allow for tailoring effective material properties beyond ("meta") the properties of their bulk ingredient materials. This statement is especially true for chiral metamaterials, as unlocking certain degrees of freedom necessarily requires broken centrosymmetry. While the field of chiral electromagnetic/optical metamaterials has become rather mature, the field of elastic/mechanical metamaterials is just emerging and wide open. This research news reviews recent theoretical and experimental progress concerning 3D chiral mechanical and optical metamaterials, with special emphasis on work performed at KIT.

Rigid biological systems are increasingly becoming a source of inspiration for the fabrication of next generation advanced functional materials due to their diverse hierarchical structures and remarkable engineering properties. Among these rigid biomaterials, nacre, as the main constituent of the armor system of seashells, exhibiting a well-defined 'brick-and-mortar' architecture, excellent mechanical properties, and interesting iridescence, has become one of the most attractive models for novel artificial materials design. In this review, recent advances in nacre-inspired artificial carbonate nanocrystals and layered structural nanocomposites are presented. To clearly illustrate the inspiration of nacre, the basic principles relating to plate-like aragonite single-crystal growth and the contribution of hierarchical structure to outstanding properties in nacre are discussed. The inspiration of nacre for the synthesis of carbonate nanocrystals and the fabrication of layered structural nanocomposites is also discussed. Furthermore, the broad applications of these nacre inspired materials are emphasized. Finally, a brief summary of present nacre-inspired materials and challenges for the next generation of nacre-inspired materials is given.

This Personal Account summarizes the recent developments in the development of self-assembled supramolecular channels and their dimensional extension towards up-scaled self-organized materials. This Personal Account begins with a short, non-exhaustive description of artificial supramolecular channel systems that are involved in water-, proton-, and ion-transport processes through bilayer membranes. Then, these "all-made" artificial systems will be described as a source of inspiration, by presenting several breakthroughs over the last few years in the field of biomimetic supramolecular channel systems. Their inclusion in artificial polymeric/hybrid matrixes, which results in the formation of biomimetic artificial materials for directional translocation through channeling pathways, will be described in the last part of the Personal Account, with an emphasis on all of the efforts that are necessary to maintain their channel-transporting function within bilayer membranes under up-scaled operating conditions.

The study of biological and biomaterials with X-rays and neutrons provides an important contribution to the understanding of the structure–function relationship in natural and artificial materials. Aside from the fundamental knowledge gained by these insights—which is of value already in itself—it helps to create new materials which are either bio-inspired or modified such that they can interact in an optimized way with the biological environment. Usually the methods applied are noninvasive and deliver information about the structure of the specimen or material parameters, in some cases even in vivo. In this paper, an overview of most recent developments in the field of biological and biomaterials studies with neutron and X-rays is given.

The emergence of multidrug-resistant bacteria associated with blood-contacting artificial materials is a growing health problem, which demands new approaches in the field of biomaterials research. In this study, a poly(sulfhydrylated polyester) (PSPE) was synthesized by the polyesterification reaction of mercaptosuccinic acid with 3-mercapto-1,2-propanediol and blended with poly(methyl methacrylate) (PMMA) from solution, leading to solid PSPE/PMMA films, with three different PSPE : PMMMA mass ratios. These films were subsequently S-nitrosated through the immersion in acidified nitrite solution, yielding poly(nitrosated)polyester/PMMA (PNPE/PMMA) films. A polyurethane intravascular catheter coated with PNPE/PMMA was shown to release nitric oxide (NO) in phosphate buffered saline solution (pH 7.4) at 37 degrees C at rates of 4.6 nmol/cm(2)/h in the first 6 h and 0.8 nmol/cm(2)/h in the next 12 h. When used to coat the bottom of culture plates, NO released from these films exerted a potent dose- and time-dependent antimicrobial activity against Staphylococcus aureus and a multidrug-resistant Pseudomonas aeruginosa strains. This antibacterial effect of PSPE/PMMA films opens a new perspective for the coating of blood-contacting artificial materials, for avoiding their colonization with highly resistant bacteria.

Triply periodic minimal surface structures and related geometries are widely identified in many natural systems, such as biological membranes and biophotonic structures in butterfly-wing scales. Inspired by their marvelous and highly symmetrical structures and optimized physical properties, these structures have sparked immense interest for creating novel materials by extracting the design from nature. Significant progress has been made to understand these biological structures and fabricate artificial materials by top-down and bottom-up approaches for numerous applications in chemistry and materials science. Herein, research achievements, including theoretical and experimental discoveries, in both biological systems and the artificial synthesis of materials with triply periodic minimal surface structures and related materials are summarized. Recent developments in self-assembled lyotropic liquid crystal phases, block copolymer systems, and their inorganic replicas are discussed in detail.

Network (sponge) and cellular structures are often seen in various types of materials. Materials with such structures are generally characterized by light weight and high mechanical strength. The usefulness of such materials is highlighted, for example, by the remarkable material properties of bone tissue, which often has a highly porous structure. In artificial materials, plastic and metallic foams and breads have such structures. Here, we describe a physical principle for producing network and cellular structures using phase separation, and its potential applications to the morphological control of materials spanning from soft to hard matter.

Metamaterials are artificial materials structured on a subwavelength scale to provide electromagnetic properties beyond those available in nature. Progress in this young field has been startlingly swift. The last year alone has seen the realization of the first optical negative-index metamaterials and the constructon of two very striking metamaterial-based devices: an invisibility cloak and a far-field lens capable of subwavelength imaging. Here, I review these developments and the key concepts that made them possible.

The purpose of this review article is to show how polymer science can contribute to the further improvement of modern dentistry. It has long been believed that the development of strong dental materials is essential to improve dentistry, and polymeric materials might not be reliable compared to metals and ceramics. It was hypothesized that the bonding of restoration materials to the tooth structure is required in order to inhibit the detachment of prostheses. However, bonding of artificial materials to natural tissues is difficult. It has been found that a polymer network interpenetrated with dental hard tissues resolves this problem, that formal bonding is not required and that protection of prepared dentin against lactic acid demineralization with an impermeable barrier is a requisite for prevention of caries. Copyright © 2007 Society of Chemical Industry

This paper presents a Raman spectroscopic study on the first artificial materials that entered the fabrication of fashion accessories at the end of the 19th century. The aim was to evaluate how such materials were incorporated into fans which were representative of that period and produced with a wide diversity of characteristics. Non-destructive Raman spectroscopy has already been successfully applied to the study of materials in heritage objects, with a near-infrared excitation (1064 nm) to avoid any fluorescence. Our study focused on cellulose-based materials, i.e. celluloid and acetocellulose, the other materials used for fan manufacture requiring another analysis technique and methodology. Raman spectra of their main components, cellulose nitrate and camphor for celluloid and cellulose acetate for acetocellulose, were used as references for the identification. The choice of the reference components is discussed. After a first selection excluding fans made of natural and/or proteinaceous materials, 13 fans were analyzed. Eleven of them were shown to be made of celluloid since their Raman spectra superposed cellulose nitrate and camphor signatures. We observed additional bands for three of these fans, which we assigned to a plasticizer added to ease modeling. Bands of triphenyl phosphate, one of the plasticizers used for acetocellulose manufacturing, were evidenced in the Raman spectra of the last two fans of our selection. Copyright © 2004 John Wiley & Sons, Ltd.

A simulated body fluid (SBF) with ion concentrations approximately equal to those of human blood plasma has been used widely for in vitro assessment of the bioactivity of artificial materials and for the formation of bone-like apatite on various substrates. The ion concentrations of a conventional SBF (c-SBF) are, however, not exactly equal to those of blood plasma. In the present study, a revision of c-SBF was made to prepare new SBFs (r-SBF, i-SBF, and m-SBF) with ion concentrations equal to or closer to those of blood plasma. The ion concentrations of the r-SBF and i-SBF were designed to be equal to those of blood plasma in total and dissociated amounts, respectively. The m-SBF was designed to have a total ion concentration equal to that of blood plasma, except for the concentration of HCO(-) (3), which was set to the saturated level with respect to calcite. The ion concentrations and pH of the as-prepared new SBFs were found to be equal to those of the nominal values. Upon sealed storage, the r-SBF and i-SBF showed no change in ion concentrations for up to 4 weeks at 5 degrees C, and up to 2 weeks at 36.5 degrees C, but thereafter they showed a decrease in HCO(-) (3) concentration and an increase in pH. Under the same storage conditions, the c-SBF and m-SBF showed no change in ion concentrations and pH values over a period of up to 8 weeks. These results indicate that the r-SBF and i-SBF are less stable than the c-SBF and m-SBF in terms of changes in ion concentrations relative to storage period. The m-SBF is optimal for in vitro bioactivity assessment of artificial materials and for biomimetic production of bone-like apatite.

We introduce an idea for a novel class of artificial materials suitable for chiral and bianisotropic waveguide structures. Fabrication of such waveguides can be achieved using modern planar technology. Chiral and bianisotropic waveguides described in this article are based on a composition of magnetostatic wave (MSW) resonators. Because of the small sizes of MSW resonators the concentration of the particles may be very high. The resonance frequency of MSW resonators may be tuned via a bias magnetic field. Therefore, we can develop a method of achieving chirality control. © 1996 John Wiley & Sons, Inc.

Nature excels at engineering materials by using the principles of chemical synthesis and molecular self-assembly with the help of noncovalent forces. Learning from these phenomena, scientists have been able to create a variety of self-assembled artificial materials of different size, shapes, and properties for wide ranging applications. An area of great interest in this regard is solvent-assisted gel formation with functional organic molecules, thus leading to one-dimensional fibers. Such fibers have improved electronic properties and are potential soft materials for organic electronic devices, particularly in bulk heterojunction solar cells. Described herein is how molecular self-assembly, which was originally proposed as a simple laboratory curiosity, has helped the evolution of a variety of soft functional materials useful for advanced electronic devices such as organic field-effect transistors and organic solar cells. Highlights on some of the recent developments are discussed.

Inorganic structures and their assemblies play important roles in artificial materials for biological applications. In this short review, we briefly summarize recent research on bioapplicable materials supported by inorganic structures possibly reflecting the concept of nanoarchitectonics, according to classification of unit nanostructures (nanoparticles, nanospheres, nanosheets, layer-structures, and nanotubes), internally nanostructured materials (mesoporous materials), organized assemblies (mainly layer-by-layer (LbL) assemblies), and hierarchical structures. Bioapplications such as sensing, drug delivery, and cell imaging are described.

Ferromagnet/semiconductor hybrid structures are attractive and promising as artificial materials for 'semiconductor spintronics', because they can possess magnetic and/or spin-related functions and they have excellent compatibility with semiconductor device structures. We review our studies on the molecular beam epitaxy (MBE) growth of ferromagnet (MnAs)/III–V semiconductor layered heterostructures and nanoscale granular structures, and their magnetic, magneto-transport and magneto-optical properties. We show that, by careful control of MBE growth and processing, some useful magnetic or spin-related functions can be realized at room temperature.

The controlled assembly of synthetic polymer structures is now possible with an unprecedented range of functional groups and molecular architectures. In this critical review we consider how the ability to create artificial materials over lengthscales ranging from a few nm to several microns is generating systems that not only begin to mimic those in nature but also may lead to exciting applications in synthetic biology (139 references).

Charles Hufnagel began the era of artificial heart valve implantation in 1952, before the existence of technology that allowed the heart to be arrested. Hufnagel implanted a Lucite tube and ball in the descending aorta with clamps that facilitated rapid insertion without arresting the heart. Although valves in the descending aorta were somewhat successful in the management of aortic insufficiency, only a device placed in the appropriate anatomical or orthotopic position could help patients with valvular stenosis. This presentation will review the development of mechanical heart, emphasizing changes in valve design resulting from our greater understanding of blood hemodynamics, the mechanical forces imposed on valve components, and the interaction of artificial materials with components of circulating blood. The evolution from polymer to metal and finally the dominance of pyrolitic carbon as the material of choice will be explored. Similarities and differences between the four bileaflet valves that have received FDA approval and the two valves with CE mark approval that have not yet received FDA approval will be discussed.

The sizes of the surface features that a cell might encounter in its natural environment span the nanometer-to-micrometer range of topographies. These environments include extracellular matrix, other cells, organisms, tissues, artificial materials, and various forms of the surface coatings or roughness that have been used for dental and orthopedic implants.

The problems encountered in the use of artificial materials in the body are discussed, using as example the artificial heart. In the quest for suitable materials, numerous investigations have been carried out, including, inter alia, studies on the adsorption of proteins on polymer surfaces and on the passivation of such surfaces by coating with proteins or by the growth of cell cultures. The development of passive artificial substances is also discussed.