In the development of high-performance organic electronics, there has been significant effort in establishing relationships between microstructure and electronic properties, which has provided a deeper understanding of device operation and has guided performance improvements. When considering flexible and stretchable organic electronics, the mechanical behavior of the active layers becomes a critical attribute alongside electronic functionality. Thus, there is a need to establish the role of film morphology on both electronic properties and thermomechanical behavior, and the relationship between mechanical and electronic properties. In this article, we highlight recent advances in establishing these important relationships and the approaches employed to manage film morphology to optimize both mechanical behavior and device performance. Additionally, in stretchable applications, the film morphology may not be static, and capturing the microstructure changes under deformation is necessary to establish structure–property relationships over the expected physical operating space. Thus, also discuss film morphology change under large deformation for various stretchable film approaches.

Many current technological applications are based on the electrical properties of materials. Among these, ferroelectricity, antiferroelectricity, paraelectricity, and resistivity are the most important to be studied and controlled. To overcome important drawbacks of sintered ceramics or single crystals with these characteristics, the preparation of glass-ceramics with these phases dispersed in a glass matrix is a possible solution. The formation of glass-ceramics shows great advantages—their properties (optical, electrical, mechanical, and chemical) can be controlled via the volume fraction of the dispersed active phase. Thus, the preparation and properties of glass-ceramics containing ferroelectric crystallites embedded in the glass matrix have received considerable interest. This article discusses state-of-the-art preparation of glass-ceramics with one important technological ferroelectric crystal, lithium niobate (LiNbO3). Since the preparation of LiNbO3 single crystals by traditional growth techniques is technically difficult and economically costly—and with dense ceramics, it is difficult to achieve a congruent composition—scientific research on the fabrication methods of inorganic glasses containing LiNbO3 crystallites is an important current topic.

The development of doped photonic glass is of fundamental importance for various applications, including telecommunication, lasers, and photovoltaics. Despite the great advances in doping techniques, a long-standing barrier remains concerning how to gain better control over the properties of active dopants in disordered systems. Here, we provide a brief overview of recent progress on the engineering of the chemical environment and chemical state of dopants in glass by tuning the topological features, including sublattices and packing manner of the network. The methods allow us to finely tune the chemical state of active dopants over a wide range of length scales, from dispersed ions to aggregated clusters to nanoparticles, and also offer new opportunities to engineer the local crystal field around active dopants. This inherent structure-based strategy leads to intriguing optical phenomena such as tunable luminescence and notable enhancements in radiative transition probability.

The continued use of finite fossil fuel resources has shifted thinking toward a potential future bioeconomy, and the field of polymer science will play a critical role in valorization of bio-derived materials. Interest in renewable resources is constantly increasing, backed up by new environmental regulations and economic considerations. Biomass is abundant and diverse, and polymeric materials based on renewable feedstocks represent a viable alternative to fossil resources. Bio-oil—a dark brown, free-flowing organic liquid mixture—is a product of fast pyrolysis or liquefaction of biomass. Bio-oil generally comprises a large amount of water and hundreds of organic chemical compounds that can be further broken down into families of reactive structures, capable of producing new synthetic pathways to design and synthesize high-performance biopolymers and bioresins using lignocellulosic biomass. These new polymeric materials have demonstrated a unique combination of thermal resistance and low cost intrinsic of the biomass utilized, as well as superior mechanical performance of polymeric resins sufficient to compete with high-performance structural resins and coating materials.

High-pressure research, whether static or dynamic, provides “windows” to novel states, transformations, and properties of highly compressed extended states of light elemental solids that may comprise the internal structures of giant planets and stars. These low-Z extended solids are extremely hard, have high energy density, and exhibit novel electronic and nonlinear optical properties—superior to other known materials at ambient conditions. These materials are often formed at formidably high pressures and are highly metastable at ambient conditions; only a few systems have been recovered at ambient conditions, limiting the materials to the realm of fundamental scientific discovery. An exciting new research area has recently emerged that aims to understand and ultimately allow for control of the stability, bonding, structure, and properties of low-Z extended solids. This article presents an overview of the basic principles that govern and control the pressure-induced chemistry in dense solids. This is aimed at identifying high energy density, low-Z extended solids that are amenable to up-scaled synthesis and stabilization at ambient conditions.

Helium ion microscopy (HIM), enabled by a gas field ion source (GFIS), is an emerging imaging and nanofabrication technique compatible with many applications in materials science. The scanning electron microscope (SEM) has become ubiquitous in materials science for high-resolution imaging of materials. However, due to the fundamental limitation in focusing of electron beams, ion-beam microscopy is now being developed (e.g., at 20 kV the SEM beam diameter ranges from 0.5 to 1 nm, whereas the HIM offers 0.35 nm). The key technological advantage of the HIM is in its multipurpose design that excels in a variety of disciplines. The HIM offers higher resolution than the best available SEMs as well as the traditional gallium liquid-metal ion source (LMISs) focused ion beams (FIBs), and is capable of imaging untreated biological or other insulating samples with unprecedented resolution, depth of field, materials contrast, and image quality. GFIS FIBs also offer a direct path to defect engineering via ion implantation, three-dimensional direct write using gaseous and liquid precursors, and chemical-imaging options with secondary ion mass spectrometry. HIM covers a wide range of tasks that otherwise would require multiple tools or specialized sample preparation. In this article, we describe the underlying technology, present materials, relevant applications, and offer an outlook for the potential of FIB technology in processing materials.

Catalysts play essential roles in the chemical vapor deposition of single-wall carbon nanotubes (SWCNTs). In this article, we summarize studies on catalysts for the structure-controlled growth and mass production of SWCNTs, discussing the main progress and the remaining challenges.

The theories of thermionic emission and field emission (also known as the Richardson–Dushman [RD] and Fowler–Nordheim [FN] Laws, respectively) were formulated more than 80 years ago for bulk materials. In single-layer graphene, electrons mimic massless Dirac fermions and follow relativistic carrier dynamics. Thus, their behavior deviates significantly from the nonrelativistic electrons that reside in traditional bulk materials with a parabolic energy-momentum dispersion relation. In this article, we assert that due to linear energy dispersion, the traditional thermionic emission and field emission models are no longer valid for graphene and two-dimensional Dirac-like materials. We have proposed models that show better agreement with experimental data and also show a smooth transition to the traditional RD and FN Laws.

The resolution of the electron microscope is now largely limited by the performance of its electron source when various aberrations in the electron imaging system, especially spherical aberrations, are corrected. A nanowire tip could be an ideal point electron source, where electrons are emitted from a small physical area. In this article, we review recent advances in electric-field-induced electron emission using a single nanowire, specifically, single-crystalline lanthanum hexaboride (LaB6) nanowire, compared to the state-of-the-art contemporary tungsten cold-field electron emitter W(310) as well as single atom tip and single-carbon nanotube emitters. Owing to its low work function, improved emission stability, and high emission brightness, the LaB6 nanowire as a cold-field-emission electron source offers a new and exciting opportunity for developing the next generation of electron microscopes.

Three-dimensional (3D) bioprinting has become a fast-developing research field in the last few years. Many different technical solutions are available, with extrusion-based printing being the most promising and versatile method. In addition, a variety of biomaterials are already available for 3D printing of live cells. The real challenge, however, remains bioprinting of macroscopic, volumetric constructs of well-defined structures since hydrogels used for cell-embedding must consist of rather soft materials. This article describes recent developments to overcome these limitations that prevent clinical applications of bioprinted human tissues. New approaches include technical solutions such as in situ cross-linking or gelation processes that now can be performed during the bioprinting process, modified bioinks that combine suitable viscosity and cytocompatible gelation mechanisms, and utilization of additional materials to provide mechanical strength to the cell-laden constructs.

Since the discovery of glass-ceramics by Stookey in the 1950s, there has been increasing demand for glass-ceramics with high strength and toughness for medical, structural, and consumer electronics markets. This article reviews recent developments in composition, microstructure, and mechanical properties of glass-ceramics, with an emphasis on their mechanical performance. It reveals that glass-ceramics with strength and toughness comparable to structural ceramics, such as Al2O3, have been successfully developed. Meanwhile, efforts are being devoted to creating glass-ceramics with further improved damage resistance. With inspiration from natural materials such as jade, baddeleyite, bone, and nacre, glass-ceramics with unique microstructures and properties have been obtained. Further progress is needed in the design of novel compositions, microstructures, and phase assemblages to activate multiple toughening mechanisms in glass-ceramics for significant improvements in strength and toughness.

Single-phase (binderless) superhard nanopolycrystalline diamond and cubic boron nitride (cBN) consisting of fine grains of several tens of nanometers without any secondary phases or binder materials have been developed. These nanopolycrystalline materials are synthesized by direct conversion sintering under ultrahigh pressure and high temperature with optimized and precisely controlled starting materials and synthesis conditions. Their hardness surpasses that of single crystals and conventional sintered compacts and is free from the characteristic cleavage and anisotropy of single crystals. They are especially promising materials for next-generation high-precision, high-efficiency cutting tools and wear-resistant tools. The nanopolycrystalline diamond has excellent potential for precision cutting of nonferrous hard materials, including cemented carbide and hard ceramics, as does the nanopolycrystalline cBN for cutting ferrous hard metals.

Among the most abundant biopolymers in the biosphere, lignin represents an untapped opportunity to create novel bioproducts. In this article, we discuss possibilities to synthesize nano- and microparticles by harnessing lignin’s inherent tendency to associate and to develop new material compositions and functions by controlling its capacity to assemble into supramolecular structures. Because lignin is biodegradable, antimicrobial, antioxidative, and carbon neutral, inexpensive industrial lignin streams could generate value-added particulate materials that preserve the structure, composition, and colloidal features inherent to this macromolecule. We present available routes for synthesis or isolation of lignin particles, including antisolvent and aerosol processing. Metallic and polymeric lignin particle hybrids for magnetic, antibacterial, catalytic, photonic, and other applications are also discussed. Overall, the facile formation of nano- and microparticles from lignins is expected to open new pathways toward future material development.

Nanotubes (NTs) with diameters less than 2 nm have been proposed for next-generation reverse osmosis membranes. At this molecular scale, the NTs are narrow enough to block salt ions and other contaminants, but still wide enough to allow water to flow along the NTs at seemingly unprecedented rates. Simulations for design of NT membranes can be challenging. On the one hand, the standard equations for water flow through pipes are not applicable at sub-2-nm scales due to the dominance of non-continuum phenomena; on the other hand, full molecular simulations are computationally intractable for flows up to laboratory or prototype scales. This article describes recent multiscale approaches to simulating flows through aligned NT membranes of various materials. These multiscale techniques offer a unique and economical solution that can shed light on sometimes conflicting experimental results and point the way to future engineering design of nanostructured membranes.

The mechanical properties of organic electronic materials and interfaces play a central role in determining the manufacturability and reliability of flexible and stretchable organic electronic devices. The synergistic effects of mechanical stress and deformation, together with other operating parameters such as temperature and temperature cycling, and exposure to solar radiation, moisture, and other environmental species are particularly important for longer-term device stability. We review recent studies of basic mechanical properties such as adhesion and cohesion, stiffness, yield behavior, and ductility of organic semiconducting materials, and their connection to underlying molecular structure. We highlight thin-film metrologies to probe the mechanical behavior, including when subjected to simulated operational conditions. We also report on strategies for improving reliability through interface engineering and tailoring material chemistry and molecular structure. These studies provide insights into how these metrologies and metrics inform the development of materials and devices for improved reliability.

We explore some aspects of the optimization of amorphous semiconductors as well as low- and high-dielectric-constant (low-/high-k) materials viewed purely from the perspective of percolation and topological constraint theories. We specifically illustrate how percolation, constraint theory, and mean network coordination, 〈r〉, play underlying roles in determining the electrical and mechanical properties of amorphous semiconducting and dielectric materials as well as interfaces that are important for modern micro-/nanoelectronic devices.

Semiconductor x-ray detectors are widely used in experiments at synchrotron facilities. The performance of these detectors depends heavily on the semiconductor material properties. Improvements in crystal growth and device processing are key to developing “high-Z” (high atomic number) semiconductors for hard x-ray detection. Germanium is the most mature high-Z semiconductor and is widely used in x-ray detectors, but it has the drawback of needing to be cooled during operation, often to cryogenic temperatures. Compound semiconductors with wide bandgaps can be used at room temperature, but crystal defects can degrade their performance. Gallium arsenide currently shows poorer energy resolution, but its comparative robustness and stability over time make it a strong option for imaging detectors. Cadmium telluride and cadmium zinc telluride both provide higher detection efficiencies at extreme x-ray energies as well as good energy resolution; the main challenge with these materials is maintaining consistent behavior under a high x-ray flux.

Electron-beam (e-beam) irradiation damage is often regarded as a severe limitation to atomic-scale study of two-dimensional (2D) materials using electron microscopy techniques. However, energy transferred from the e-beam can also provide a way to modify 2D materials via defect engineering when the interaction of the beam with the sample is precisely controlled. In this article, we discuss the atomic geometry, formation mechanism, and properties of several types of structural defects, ranging from zero-dimensional point defects to extended domains, induced by an e-beam in a few representative 2D materials, including graphene, hexagonal boron nitride, transition-metal dichalcogenides, and phosphorene. We show that atomic as well as line defects and even novel nanostructures can be created and manipulated in 2D materials by an e-beam in a controllable manner. Phase transitions can also be induced. The e-beam in a (scanning) transmission electron microscope not only resolves the intrinsic atomic structure of materials with defects, but also provides new opportunities to modify the structure with subnanometer precision.

Biological systems illustrate how complex and dynamic physical and chemical interactions between many different components can produce organized structures across length scales, ranging from angstroms to hundreds of meters, and precise temporal control over diverse material dynamics. While mechanisms for pattern formation such as reaction-diffusion processes, message passing, or rule-based assembly have been studied extensively using mathematical models, it can be difficult to create synthetic materials that implement these mechanisms. Here, we describe how DNA nanotechnology techniques make it possible to systematically build systems capable of complex self-organization or pattern formation across scales. DNA-programmed short-range interactions can be used to build aperiodic crystals and assemblies with long-range order, form patterns using reaction-diffusion and chemical message passing, and create self-organizing or stimulus-responsive amorphous materials, including gels or cell-sized compartments. Exploiting principles from self-organization using DNA-based interactions makes it possible to build materials with complex long-range order and intelligent spatiotemporal responses to a variety of stimuli using relatively simple bottom-up methods.

Because of its unique properties and promising applications, graphene has attracted great interest from both academia and industry in the last decade. For studies on graphene as well as for applications, it is essential to develop techniques to prepare graphene in a controllable way. Graphene can be produced in the form of nano-/microflakes using a top-down method by the exfoliation of graphite or the reduction of graphene oxide, or in the form of a film or foam in a bottom-up method, predominantly by chemical vapor deposition of carbon precursors on catalytic substrates. This article focuses on the catalytic substrates, especially metals, used for graphene growth. We also discuss graphene growth mechanisms and kinetics, control of the number of graphene layers and their stacking order, engineering of large-area graphene single crystals, as well as low-temperature growth.