Metal–organic framework (MOF) materials are well known as elegant gaseous energy-storage materials, but their potential for electrical energy storage has only recently been explored. Although numerous studies have focused on MOF-derived porous carbon or nanoscale metal oxide materials, less attention has been paid to the intrinsic properties achievable through the molecular design of MOFs. Indeed, the porous nature of MOF architectures is highly suitable for accommodating electrolyte ions in electrochemical processes, suggesting their potential as high-performance active materials for batteries. In this article, we consider recent examples employing MOF materials as battery electrode materials. Redox-active sites were incorporated on metal junctions, ligands, or both, in the MOF structures. In addition, we introduce novel electrochemical mechanisms observed in the electrochemical process of MOF electrode materials.

Establishing strategies for high-resolution micrometer to subnanometer structural control is an essential feature of any versatile materials design paradigm. Colloidal crystal (CC) templating not only establishes tunable replica pore topologies, but interfacial- and confinement-mediated phenomena extend its impact for tailoring properties such as pore hierarchy, topological diversity, and macroscopic morphology, as well as nucleation, growth, and crystallinity. Coupled with emerging strategies for “single-pot” template-replica co-assembly and efforts to expand the accessible materials palette, CC-templating offers promise for application-driven, rational materials design.

NiTi alloys are well known not only due to their exceptional shape-memory ability to recover their primary shape, but also because they show high ductility, excellent corrosion and wear resistance, and good biological compatibility. They have received significant attention especially in the field of laser additive manufacturing (AM). Among laser AM techniques, selective laser melting and laser metal deposition are utilized to exploit the unique properties of NiTi for fabricating complex shapes. This article reviews the properties of bulk and porous laser-made NiTi alloys as influenced by both process and material parameters. The effects of processing parameters on density, shape-memory response, microstructure, mechanical properties, surface corrosion, and biological properties are discussed. The article also describes potential opportunities where laser AM processes can be applied to fabricate dedicated NiTi components for medical applications.

In a manner reminiscent of macroscale bending and folding techniques such as origami, the out-of-plane assembly of lithographically micro- and nanopatterned thin films, can be used to fabricate three-dimensional (3D) micro- and nanostructured devices. These 3D devices, including microelectronic circuits, sensors, antennas, metamaterials, robotic, and biomimetic constructs, enable new functionalities and are challenging to fabricate by other methods. In this article, we summarize important features of this set of techniques and the devices assembled thereof, with a focus on functional constructs that have been formed by bending, folding, or buckling. At small size scales, manipulation using manual or even wired probes face daunting practical challenges in terms of cost, scalability, and high-throughput manufacturability; hence we emphasize techniques that manipulate strain in thin films so that they can spontaneously assemble into programmed 3D geometries without the need for any wires or probes.

Quantum information and computing are at the forefront of computer science, but their implementation relies on significant developments in materials science. In particular, suitable, lattice-matched substrates for two promising approaches—electrostatically defined quantum dots in Si/SiGe heterostructures, and superconducting circuits containing Josephson junctions—do not exist. Instead, these approaches rely on metamorphic substrates. In this article, we focus on the general structure and requirements of SiGe quantum dot heterostructures, the demands they impose on the underlying substrate, and the impact that properties of the metamorphic substrate have on device performance. Superconductor Josephson junction materials are briefly discussed in a similar fashion, and opportunities for future developments in both systems are described.

Methods used in informatics require input data that are in a machine-readable, structured format. Materials data, in particular, can be exceedingly complex, so defining data formats to store any and all materials-related information is a daunting task. In this article, we discuss a hierarchical data structure used for storing materials data called the physical information file (PIF). The PIF is a flexible schema for storing the structure, processing history, and properties of materials, devices, and physical systems. In addition to a general discussion of the schema, we give examples of its use in representing complex materials systems. We also describe open-source tools that have been developed for building and reading files using the PIF schema.

X-ray absorption spectroscopy (XAS) is a widely used characterization technique to explore the local geometric and electronic structures of materials with element specificity. XAS measurements are performed at synchrotron radiation sources that provide brilliant, tunable, and monochromatic energy photons. The advantages of XAS include good elemental, chemical, and orbital sensitivities, which all stem from inherent electron excitation and transition processes. XAS is categorized into soft (<2000 eV) and hard (>5000 eV) x-ray regimes, based on the incident photon energy. Soft x-rays can probe the K-edges of low-Z (atomic number) elements, including Li, C, N, O, and F, and the L-edges of 3d transition metals, whose K-edge is within the hard x-ray regime. All of these elements are essential components of energy materials. This article introduces the principle of XAS and reviews some recent applications in energy storage and energy conversion, illustrating the capabilities of XAS to investigate the fundamental properties of materials from the points of view of atomic and electronic structures, which play crucial roles in understanding the reaction mechanisms in high-performance devices.

A series of recent instrumental advances have facilitated the application of atom probe tomography (APT) to the characterization of an increasingly wide range of materials and devices. Whereas APT was previously mostly limited to the analysis of alloys, advances in areas such as laser pulsing and detectors have enabled characterization of semiconductors and brittle materials. Most recently, ultraviolet laser pulsing has facilitated the analysis of materials previously considered not viable for the atom probe, such as minerals and large bandgap insulator materials. The development of in situ gas reaction cells fully integrated in atom probe instruments has enabled the characterization of surface reactions of materials exposed to highly controlled environments. Finally, current work toward an integrated cryo-transfer system is anticipated to create new directions for APT research.

Controlling the interactions of light with matter is crucial for the success and scalability of materials-processing applications. When ultrashort pulsed lasers are used, the optimal interplay between the laser and the material parameters enable highly precise and controllable fabrication, allowing structuring down to the nanometer scale. Besides this, a unique aspect for many applications is the possibility of material modifications at multiple length scales, leading to complex micro- and nanoscale architectures, while adding a new dimension to optimization of the structures. As a result, femtosecond laser micro-/nanoprocessing offers unique capabilities for three-dimensional, material-independent modification, opening new opportunities for innovation and exploitation in the materials industry. This article focuses on the implementation of ultrashort pulsed laser-based micro- and nanofabrication methodologies for the realization of structures relevant to biomimetic, fluidic, and biological applications. The wealth of possibilities and the number of new approaches for obtaining complex high-resolution features at the micro- and nanoscales are demonstrated.

The electron microscope has made paramount contributions to understanding the structure of biological molecules, cells, and tissues. In general, the most faithful preservation of biological specimens and other soft-organic materials is achieved through cryogenic fixation. The embedding medium is the native aqueous environment itself, immobilized in vitrified form by rapid or pressurized cooling. Until recently, imaging of such vitrified thin specimens by electron cryo-microscopy has been nearly synonymous with wide-field transmission electron microscopy (TEM). Several new approaches have entered the cryo-microscopy field, including soft x-ray imaging, serial surface imaging using focused ion beam scanning electron microscopy, phase plates, and scanning TEM (STEM). In this article, we focus on the STEM method and its adaptation to biological cryo-microscopy. Cryogenic imaging of unstained specimens by STEM introduces specific challenges. Difficulties were long considered insurmountable, and the potential advantages were underappreciated. Future developments in experimental setup and detector technologies will allow for extension of the method to thicker specimens with improved resolution and analytic capabilities.

Nanoparticles (NPs) have emerged as new functional blocks for optical, energy, and biomedical applications, opening a new frontier of rational self-assembly of materials. One of the most controllable assembly strategies relies on programming interparticle interactions using the complementarity of DNA strands, providing selective and reversible interactions between particles of different sizes and shapes. Much progress has been achieved in DNA-guided assembly of particle superlattices. By tuning the interactions, sizes, and shapes of NPs, a wide variety of structures have been assembled. This article discusses the most significant achievements and challenges in assembly of DNA-programmable particle superlattices.

This article focuses on in situ transmission electron microscope (TEM) characterization to explore twins in face-centered-cubic and body-centered-cubic monolithic metals, and their impact on the overall mechanical performance. Taking advantage of simultaneous nanomechanical deformation and nanoscale imaging using versatile in situ TEM tools, direct correlation of these unique microscopic defects with macroscopic mechanical performance becomes possible. This article summarizes recent evidence to support the mechanisms related to strengthening and plasticity in metals, including nanotwinned Cu, Ni, Al, Au, and others in bulk, thin film, and nanowire forms.

This article summarizes recent research on laser-based processing of two-dimensional (2D) atomic layered materials, including graphene and transition-metal dichalcogenides (TMDCs). Ultrafast lasers offer unique processing routes that take advantage of distinct interaction mechanisms with 2D materials to enable extremely localized energy deposition. Experiments have shown that ablative direct patterning of graphene by ultrafast lasers can achieve resolutions of tens of nanometers, as well as single-step pattern transfer. Ultrafast lasers also induce non-thermal excitation mechanisms that are useful for the thinning of TMDCs to tune the 2D material bandgap. Laser-assisted site-specific doping was recently demonstrated and ultrafast laser radiation under ambient air environment could be used for the direct writing of high-quality graphene patterns on insulating substrates. This article concludes with an outlook on developing further advanced laser processing with scalability, in situ monitoring strategies, and potential applications.

Due to the scarcity of “easy slip” systems in hexagonal materials with a hexagonal close-packed structure (hcp), deformation twinning plays a crucial role in determining mechanical properties and texture evolution. In this article, we highlight the current understanding of mechanisms and mechanics of the twinning system $\left\{ {10\bar 12} \right\}\left\langle {10\bar 1\bar 1} \right\rangle $, which is commonly activated in all hexagonal materials for nucleation and propagation of deformation twins, twin–twin interactions, solute segregation at twin boundaries, and the development of constitutive models that account for the fundamental mechanisms of twinning/detwinning. Future directions such as characterizing the three-dimensional shapes of twins, the influence of solute atoms on twin propagation, and the influence of twin–twin junctions on mechanical properties of the hexagonal materials are discussed.

The intricate hierarchical microstructures typical of biological materials give rise to fascinating combinations of anisotropic mechanical properties that can surpass those of man-made materials. The linking together of three-dimensional (3D) imaging techniques has the potential to reveal these structures in unprecedented detail. However, a complete understanding can only be reached if the relationship between structure and mechanical properties can be elucidated. X-ray-computed tomography (CT) is uniquely placed to image such structures across a wide range of length scales. We review recent technical advances that are leading to improved contrast and spatial resolution. We highlight how time-lapse CT 3D studies can track the response of hierarchical microstructures to mechanical loading.

The capabilities of metal additive manufacturing (AM) are evolving rapidly thanks to both increasing industry demand and improved scientific understanding of the process. This article provides an overview of AM of the Ti-6Al-4V alloy, which has essentially been used as a yardstick to gauge the capability of each metal AM process developed to date. It begins by summarizing the metal AM processes existing today. This is followed by a discussion of the macro- and microstructural characteristics, defects, and tensile and fatigue properties of AM Ti-6Al-4V by selective laser melting, laser metal deposition (both powder and wire), and selective electron-beam melting compared to non-AM Ti-6Al-4V. The tensile and fatigue properties of as-built AM Ti-6Al-4V (with machined or polished surfaces) can be made comparable, or even superior, to those of Ti-6Al-4V in the most commonly used mill-annealed condition. However, these properties can exhibit a large degree of scatter and are often anisotropic, affected by AM build orientations. Post-AM surface treatments or both the post-AM surface and heat treatments are necessary to ensure the minimum required properties and performance consistency. Future directions to further unlock the potential of AM of Ti-6Al-4V for superior and consistent mechanical properties are also discussed.

Rapid increases in global energy use and growing environmental concerns have prompted the development of clean and sustainable alternative energy technologies. Electrical energy storage (EES) is critical for efficiently utilizing electricity produced from intermittent, renewable sources such as solar and wind, as well as for electrifying the transportation sector. Rechargeable batteries are prime candidates for EES, but widespread adoption requires optimization of cost, cycle life, safety, energy density, power density, and environmental impact, all of which are directly linked to severe materials challenges. This article presents a brief overview of the electrode materials currently used in lithium-ion batteries, followed by the challenges and prospects of next-generation insertion-reaction electrodes and conversion-reaction electrodes with a Li+ working ion. Finally, we discuss future directions involving solid electrolytes, multi-electron transfer hosts, and other working ions.

A review of recent literature supports the notion that organisms may achieve nanoscale control over the hierarchical assembly of organic–inorganic materials by compartmentalizing reactions into small volumes containing specifically functionalized macromolecules. Such confinement may introduce a degree of determinism to the stochastic process of nucleation by greatly reducing the number of nucleation events, allowing an organism to control nucleation using “soft” organic substrates. In this way, the polymorph, orientation, shape, and size of a crystalline building block can be selected, and its assembly into a larger structure orchestrated by the organic matrix.

The development of new hierarchical materials capable of efficient energy transfer along a predesigned pathway will boost various applications, ranging from organic photovoltaics to catalytic systems. Due to their exceptional tunability and structural diversity, metal–organic frameworks (MOFs) offer a unique platform to study and model directional energy-transfer processes and, thereby, an efficient path for energy utilization. This article summarizes the latest advances in MOF applications in the fields of optoelectronics, photoswitching, sensing, and photocatalysis, for which development is highly dependent on fundamental studies of MOF photophysics.