The use of crystals other than silicon for x-ray optics is becoming more common for many challenging experiments such as resonant inelastic x-ray scattering and nuclear resonant scattering. As more—and more specialized—spectrometers become available at many synchrotron radiation facilities, interest in pushing the limits of experimental energy resolution has increased. The potentially large improvements in resolution and efficiency that nonsilicon optics offer are beginning to be realized. This article covers the background and state of the art for nonsilicon crystal optics with a focus on a resolution of 10 meV or better, concentrating on compounds that form trigonal crystals, including sapphire, quartz, and lithium niobate, rather than the more conventional cubic materials, including silicon, diamond, and germanium.

DNA nanostructures are a set of materials with well-defined physical, chemical, and biological properties that can be used on their own or incorporated with other materials for many applications. Herein, the practical aspects of utilizing DNA nanostructures (structural or dynamic) as materials are comprehensively covered. This article first summarizes properties of DNA molecules and practical considerations and then discusses the fundamental design principles of structural DNA nanostructures. Finally, various aspects of dynamic DNA nanostructure-based actuation and computation are included.

Nanoscale electron sources with high electron-emitting performance are of great interest in vacuum nanoelectronics. Resembling traditional thermionic emission sources based on a hot tungsten filament, a hot carbon nanotube or graphene can function as a nanoscale electron source because of its excellent thermal stability and electrical conductivity. In this article, studies of thermionic emission from single hot carbon nanostructures are overviewed, emphasizing their differences in physics from macroscopic thermionic emission as well as potential applications in vacuum nanoelectronics. Due to their low dimensionality, nanoscale size, and nonequilibrium electron distribution, Richardson’s Law, which governs thermionic emission from macroscopic metals, breaks down in the case of thermionic emission from single carbon nanostructures, and an internal electric field in a carbon nanostructure can contribute directly to its thermionic emission. Graphene-based nanoscale thermionic emission sources, source arrays, and vacuum transistors have been fabricated and demonstrated to exhibit the advantages compared to those based on field emission. The advances imply the promise of realizing high-performance nanoscale electron sources and vacuum electronic devices based on thermionic emission.

“Bottom-up” assembly of fully functional cell-based materials has enormous potential for replicating endogenous tissues. Currently, most tissue-engineering strategies are based on incorporating dissociated cells into an artificial three-dimensional matrix of supportive structural elements that direct cellular migration, proliferation, and organization. The matrix provides “top-down” guidance cues that impose assembly directions on the cells; however, the matrix also competes for space and limits fully functional, cell-dense tissues. This article focuses on bottom-up fabrication of functional tissue by cell sheet engineering. Cell sheet engineering is based on the sequential stacking and adhesion of confluent and organized cell monolayers from two-dimensional cell culture without the need for artifical scaffolds or structural intermediates. The resulting functional cellular monolayers (either individually or as stacked sheets) can then be directly implanted into living systems. Clinical successes are highlighted as well as attempts to overcome the vascularization limit often observed in engineered tissues.

New developments in manufacturing and automation, from three-dimensional printing to the “Internet of things,” signify dramatic changes in our society. The push toward quantum materials is driving device fabrication toward atomic precision. Recent results suggest that scanning transmission electron microscopy (STEM) with sub-angstrom scale beams could offer a solution. However, a detailed theoretical understanding of the interaction of the electron beam with solids is needed to form a basis for new technology. This article summarizes the existing literature on electron-beam interactions with solids with a focus on irreversible transformation. We further suggest that the theoretical framework of a two-temperature model developed for fast ion damage in solids could be applicable to predicting the effects of fast electrons. Recent results from STEM-directed epitaxial growth on crystalline–amorphous interfaces are discussed in detail. Finally, perspectives on the development of this field in the near future are offered.

Transport properties of fluids in nanopores are of both fundamental as well as practical interest. Water flow in carbon nanotubes (CNTs) has received significant attention since the early 2000s for technological applications of CNTs. In this article, we provide a brief overview of modeling the slip and flow enhancement of water in CNTs. A number of experimental and computational studies have found water to flow very fast in CNTs, but the measured flow rates, which are high compared to classical hydrodynamics predictions, are scattered over 2–5 orders of magnitude. Slip lengths of 1 to 500,000 nm, resulting in almost zero to 500,000 flow enhancement, are reported for water in CNTs with diameters of 0.8 to 10 nm. We highlight some challenges in modeling fluid flow in nanopores and outline a few research directions that may resolve the order of slip and flow enhancement of water in CNTs in computational studies.

Refraction through curved surfaces, reflection from curved mirrors in grazing incidence, and diffraction from Fresnel zone plates are key hard x-ray focusing mechanisms. In this article, we present materials used for refractive x-ray lenses. Important properties of such x-ray lenses include focusing strength, shape, and the material’s homogeneity and absorption coefficient. Both the properties of the initial material and the fabrication process result in a lens with imperfections, which can lead to unwanted wavefront distortions. Different fabrication methods for one-dimensional and two-dimensional focusing lenses are presented, together with the respective benefits and inconveniences that are mostly due to shape fidelity. Different materials and material grades have been investigated in terms of their homogeneity and the absence of inclusions. Single-crystalline materials show high homogeneity, but suffer from unwanted diffracted radiation, which can be avoided using amorphous materials. Finally, we show that shape imperfections can be corrected using a correction lens.

Glass-ceramics have gained considerable importance for applications in high-energy technology. Li- and Na-superionic ion-conducting ceramics find widespread use in lithium- and sodium-ion batteries as separators, solid electrolytes, and cathode materials. The ionic conductivity of these materials is influenced by crystal chemical parameters and can be further optimized via microstructural control using glass-ceramic processing. This article summarizes the most promising glass-ceramic material systems currently in use, detailing recent progress in understanding their structure–property–performance relationships. We also highlight the power and potential of solid-state nuclear magnetic resonance techniques for providing quantitative knowledge about structure, phase composition, and ion dynamics in these materials.

Paper is a material made from renewable resources, and it has been used intensively for almost 2000 years. It is a highly porous, bendable, and foldable flat structure of randomly arranged and connected fiber-like basic building blocks. The capability to transport fluids without pumps and sophisticated dosing systems is attractive. Paper microfluidics especially has gained increasing interest, particularly in the last decade. Although a number of interesting demonstration devices for easy-to-use diagnostic systems have been reported, only a limited number of these have found applications. This is mainly due to the geometric and chemical complexity of the material. While chemical functionalization (e.g., for defining hydrophobic barriers for spatially resolved fluid transport) is well advanced, understanding and controlling capillary-driven transport of a fluid within the complex porous matrix of paper. This article highlights recent advances and outlines design strategies for successful microfluidic paper-based applications.

When the size and spacing of catalyst nanoparticles are well controlled on a substrate, carbon nanotubes (CNTs) can grow and assemble into a unique, vertically aligned structure frequently called a “forest.” Long, aligned, and pure CNTs can easily be synthesized in simple or highly complex configurations. First reported in 1996, CNT forests have been shown to be unique and useful forms of CNTs, as they have spurred the development of novel processes and applications and in addition, served as test beds for investigations into CNT growth mechanisms. This article provides an overview of two decades of research in this area.

Three-dimensional (3D) printing has expanded beyond the mere patterned deposition of melted solids, moving into areas requiring spatially structured soft matter—typically materials composed of polymers, colloids, surfactants, or living cells. The tunable and dynamically variable rheological properties of soft matter enable the high-resolution manufacture of soft structures. These rheological properties are leveraged in 3D printing techniques that employ sacrificial inks and sacrificial support materials, which go through reversible solid–fluid transitions under modest forces or other small perturbations. Thus, a sacrificial material can be used to shape a second material into a complex 3D structure, and then discarded. Here, we review the sacrificial materials and related methods used to print soft structures. We analyze data from the literature to establish manufacturing principles of soft matter printing, and we explore printing performance within the context of instabilities controlled by the rheology of soft matter materials.

DNA nanotechnology has the power to form self-assembled and well-defined nanostructures, such as DNA origami, where the relative positions of each atom are known with subnanometer precision. Our ability to synthesize oligonucleotides with chemical modifications in almost any desired position provides rich opportunity to incorporate molecules, biomolecules, and a variety of nanomaterials in specific positions on DNA nanostructures. Several standard modifications for oligonucleotides are available commercially, such as dyes, biotin, and chemical handles, and such modified oligonucleotides can be applied directly for integration in DNA nanostructures. In another approach, various molecules and nanomaterials have been functionalized with DNA for incorporation in DNA nanostructures by hybridization to staple strands extending from the origami structure. Multiple copies of functionalities such as hydrocarbons or steroids have been introduced to change the surface properties of DNA origami structures, either to protect the DNA nanostructure or to dock it into membranes and other hydrophobic surfaces. DNA nanostructures have also been used to control covalent chemical reactions. This article provides an introduction to chemical methods applied to DNA nanotechnology and, through examples, shows how this increases the potential of DNA nanostructures as functional nanomaterials.

Light-induced generation of free electrons is of interest for a wide variety of vacuum electronic devices and systems. The properties of nanomaterials, stemming from their geometry and the strong manifestation of quantum phenomena in them, have opened up new avenues for developing new cathodes and exploring and exploiting electron emission. This article presents the heat trap effect—efficient localized heating of carbon nanotube arrays using light, leading to electron emission through the thermionic mechanism. This process requires unexpectedly modest amounts of optical power—available from sources such as handheld lasers—and dramatically simplifies the electron emitter. Potential applications, including thermionic and thermoelectric conversion for solar-energy harvesting and simple electron-beam systems, are also highlighted.

High pressure is a fascinating tool to promote and enhance the properties of materials as well as to induce new and exotic phenomena. This is especially of interest for functional materials, which are very sensitive to external pressure (P) and whose features can be tuned and controlled in a rigorous fashion. Through specific examples of the role of applied P on two families of functional compounds based on the perovskite lattice, manganites, and organic–inorganic hybrid perovskites, it is shown that the particular properties of interest can be manipulated by means of pressure. Examples highlight the effects at both the microscopic and macroscopic level, and show how the understanding of P-induced phenomena is essential for the development of materials chemistry design.

The properties and functionalities of inorganic glasses can be tuned by adjusting their chemical composition and, in turn, their atomic-scale structure. However, accurate prediction of glass properties from composition has traditionally been impossible. Recent progress in temperature-dependent constraint theory paves the way for the design of new multicomponent glasses with tailored properties. Atoms in network glasses are constrained by their chemical bonds and bond angles, and the strength of these constraints depends on the local topology and the chemical nature of the elements. By counting the number of constraints around both network-forming and network-modifying atoms as a function of both composition and temperature, it is possible to make quantitative connections among composition, structure, and certain macroscopic properties. Here, we review recent developments in glass-structure determination and modeling. We then demonstrate how the structural information is used as input for topological predictions of glass properties such as viscosity and hardness. These predictions enable the design of novel industrial glasses with desired properties and manufacturing attributes.

Stretchable devices, with the capability of retaining their functionalities under stretching, are drawing much attention as a promising solution to address the mechanical mismatch between traditional stiff electronics and soft curvilinear biological systems. Intensive efforts have been made toward the advancement of stretchable devices, such as the development of novel mechanically durable materials, deformable conductors and circuits, novel processing methods, and elastic matrixes for stretchable substrates and system integration. Among these, the elastic substrate constitutes the component that bears the applied strain and thus endows the device with stretchability, rendering its properties crucial to the overall performance of stretchable devices. This article provides a summary of the elastic materials commonly employed as stretchable substrates, as well as reveals fundamental insights into the properties requirements in the selection of stretchable substrates. Important challenges and strategies in the development of elastic matrices for stretchable devices are also discussed.

Bioprinting promises to create three-dimensional in vitro models to study pathological states and possible new therapies, and in the future, to produce complex tissue and organ replacements. This article will describe the recent advances in bioprinting technologies to engineer artificial tissues and organs by controlling spatial heterogeneity of chemical and physical properties of scaffolds and, at the same time, the cellular composition and spatial arrangement. Despite significant technological improvements in recent years, the positioning at the micrometric level and the switching of different cell types and biomaterials remain a challenge, which limits the development of resilient vascular, neural, and lymphatic networks for metabolites, signaling, and waste transport, and thus limits the development of thick and clinically relevant engineered vascularized tissues.

Diamond features a unique combination of outstanding physical properties perfect for numerous x-ray optics applications, where traditional materials such as silicon fail to perform. In the last two decades, impressive progress has been achieved in synthesizing diamond with high crystalline perfection, in manufacturing efficient, resilient, high-resolution, wavefront-preserving diamond optical components, and in implementing them in cutting-edge x-ray instruments. Diamond optics are essential for tailoring x-rays to the most challenging needs of x-ray research. They are becoming vital for the generation of fully coherent hard x-rays by seeded x-ray free-electron lasers. In this article, we review progress in manufacturing flawless diamond crystal components and their applications in diverse x-ray optical devices, such as x-ray monochromators, beam splitters, high-reflectance backscattering mirrors, lenses, phase plates, diffraction gratings, bent-crystal spectrographs, and windows.

This article discusses the modeling of liquid flow inside nanotube membranes. Applying known simplifications to the classical fluid model leads to the so-called Hagen–Poiseuille equation, which predicts no flow for diameters up to 1 nm, and very modest flows in nanochannels up to 100 nm. The main feature of classical fluid dynamics that negates the possibility of high flow is the assumption that fluid molecules closest to the channel wall stick to it, the no-slip boundary condition. In the past 10 years, a wealth of experimental evidence has, on the contrary, demonstrated significant water flow in nanotubes with diameters equal to or smaller than 1 nm, opening the possibility of nanotube membranes capable of high flows and fine separation. These high flows have also been observed in molecular dynamics simulations, particularly for water flowing through carbon nanotubes, showing the presence of strong water slip near the walls of the nanotubes. The term “flow enhancement” has been introduced to refer to the ratio of predicted (or measured) flows and the no-slip Hagen–Poiseuille equation. Both experimental and modeling results point to a strong effect on flow enhancement of the interaction between the fluid and the tube’s wall, particularly the wall surface chemistry and structure.

Structural DNA nanotechnology has been particularly driven toward three-dimensional (3D) construction since its inception at the start of the 1980s. Part of the driving force was the goal of building specific crystals from macromolecular components, without having to use trial and error for determining appropriate crystallization conditions. With the first demonstration of DNA attachment to gold nanoparticles in the 1990s, DNA became a player in inorganic nanomaterials as a programmable agent for structure assembly. For pure DNA structures, the crystallization goal has been mediated by sticky-ended cohesion with some success, although trial and error crystallizations have produced better diffracting crystals than those directed self-assembly. For nanoparticles, different types of 3D nanoscale crystalline organizations have been realized. Recent efforts not only expand the diversity of particle lattices, but also strive to achieve designed lattice symmetries and their transformations. In this article, we review the development of 3D assembly of DNA and DNA-guided nanoparticle arrays, the issues that have prevented and facilitated formation of such structures, and recent strategies toward this goal.