Thermoelectronic energy conversion can potentially provide an exceptionally efficient way to convert heat into electric power. Key components of such converters are materials with designed, small work functions. We present the principles of thermoelectronic energy conversion and discuss the advantages and challenges of the conversion process, as well the state of the art of the respective research.

A wide range of materials and material combinations, from hard and brittle to soft and elastic, is now available for the design of ultraflexible organic electronic circuits. Potential applications range from large-area active-matrix sensor arrays to displays, usable in next-generation smart appliances for mobile health, sports, and well-being. Weight and flexibility dominate the mechanical response and perception of such electronic skins, and have been developed into key figures of merit in circuit design. We review the design of thin (0.3–3 µm), ultralight (0.7–6 g/m2) large-area “imperceptible” electronic foils employing low-cost fabrication techniques compatible with mass production.

Multimaterial bioprinting technologies offer promising avenues to create mini-organ models with enhanced tissue heterogeneity and complexity. This article focuses on the application of three-dimensional bioprinting to fabricate organ-on-a-chip systems for in vitro drug testing and screening. We illustrate the capabilities and limitations of a bioprinting approach compared to microfabrication in constructing an organ-on-a-chip device. Further, we propose strategies in multimaterial integration for printing microphysiological tissue models. With these analyses, key challenges and future directions are highlighted.

Enzyme sequestration and compartmentalization are key factors in cell signaling and metabolism, evolved to solve the challenges of slow turnover rates, undesired pathway intermediates, and competing reactions. Inspired by nature, DNA nanoengineers have developed organizational systems to confine enzymes in two- and three-dimensional environments and to actuate them in response to precise external stimuli. DNA-scaffolded enzymes have applications for not only the in vitro reconstitution of proteins, peptides, and other molecular assemblies, but also to enable the generation of advanced functional nanomaterials for the development of, for example, fuel cells, biosensors, and drug delivery systems. Despite several challenges that still remain unsolved, the use of DNA scaffolds to arrange enzymes in space and time will help to realize biochemical nanofactories, where multiple components work together to produce novel and improved functional materials, rivaling the efficiency of biological systems.

High-quality carbon nanotubes (CNTs) and graphene synthesized by chemical vapor deposition (CVD) have unique one- and two-dimensional structures made up of sp2-hybridized carbon atoms and excellent physical and chemical properties. They have shown potential for use in electronics, optoelectronics, energy-storage devices, composites, and sensors. In this article, we review important milestones in these uses of CNTs and graphene produced by CVD, with special emphasis on the latest advances and remaining challenges. The key characteristics and advantages of CNTs and graphene synthesized by CVD for different applications are compared, and future trends in the use of these nanocarbons are discussed.

Rigidity theory is an extraordinary tool to understand glasses. This article demonstrates how this model can help in understanding the link between structure, dynamics, and subtler properties such as drift and aging, in particular, in phase-change materials (PCMs). First, a map of flexible/rigid regions in the Ge-(Sb)-Te system is drawn on the basis of atomistic structures modeled either by ab initio or reverse Monte Carlo techniques. A clear link between the flexible/rigid nature of the glass and its aging behavior is shown through resistivity drift as a function of composition measurements in amorphous GexTe100–x. In the particular case of amorphous GeTe, application of rigidity theory indicates that the average number of mechanical constraints decreases during aging, making the glass less stressed-rigid. Finally, the stability of PCMs also depends on the topology of the materials. The increasing number of constraints in GeTe when doped with C or N results in increased stability of the PCM.

High pressures have a significant impact on the structure-related properties of glass and are encountered in scenarios ranging from fracture mechanics, where stresses in the gigapascal regime are easily generated by sharp-contact loading, to the manufacture of permanently densified materials with tuned physical characteristics. Here, we consider pressure-induced structural changes that occur in glass and show that, for oxide materials, the oxygen-packing fraction plays a key role in determining when these changes are likely to occur. Fivefold coordinated Si atoms appear as important intermediaries in the pressure-induced deformation of silica glass.

Metamaterials are artificial materials with emerging physical properties that go well beyond those of their individual constituents, providing interesting opportunities to tailor interactions between waves and matter. This article provides an overview of recent research activity in electromagnetics, nano-optics, acoustics and mechanics, showing how suitably tailored meta-elements and their arrangements open exciting venues to manipulate and control waves in unprecedented ways. Theoretical and experimental efforts to realize metamaterials for scattering suppression, nanostructures and metasurfaces to control wave propagation and radiation, large nonreciprocity in bulk materials without magnetism, giant nonlinear responses in properly tailored metasurfaces, and metasurfaces with balanced loss and gain are discussed. Physical insights into the exotic phenomena behind the metamaterial responses, new devices based on these concepts, and their impact on technology are also discussed.

Agricultural soils are among the depositories of engineered nanomaterials (ENMs). Soil exposure to ENMs occurs through the intentional use of nano-agrochemicals, as well as through incidental contamination from industrial-waste release, irrigation with wastewater or gray water, amendment with ENMs-loaded sludge (soil conditioning to stimulate plant growth), or atmospheric fallouts. Concerns about ENM interactions with plants raise two questions. (1) Are ENMs taken up from soil by plants? (2) If they are taken up, do they remain in the nanoform within plant tissues? Experiments with crop plants have demonstrated that some ENMs such as TiO2 are taken up by roots and translocated to aboveground tissues, including fruits, without biotransformation. CeO2 ENM is also taken up by the roots; however, although most of it remains as ENM, it releases cerium ions that are incorporated into organic compounds. CeO2 ENM has been shown to be translocated from roots to seeds in soybean grown in soil amended with such ENM. On the other hand, ZnO ENM is transformed at the soil/root interface, leading to tissue Zn enrichment. Overall, most ENMs are taken up by plants with either low or no transformation, and accumulate in tissues.

Technologies for detecting and analyzing a single molecule help us understand and engineer numerous phenomena observed in nature. Carbon nanotubes (CNTs) are highly efficient molecular conduits due to their atomically smooth surface. Because of their small diameters, comparable to the size of a single molecule, even a single blocking molecule can obstruct CNT fluidic channels. Analyzing these pore-blocking events in CNTs therefore enables single-molecule studies. The high-aspect ratios of CNT channels, which extend the time scale of transport, allow for studying molecular transport that is too fast to record in other systems. Both theoretical studies and ensemble experimental measurements have verified the enhanced flow of various ions and molecular species in CNTs. Experimental measurements of a single-CNT fluidic channel, however, have only recently begun, demonstrating the detection of individual DNA, polymer, and alkali-metal ions. This article reviews recent advances in single-nanotube fluidic channels with a focus on experimental measurements.

Indirect detection is a versatile way to detect hard x-rays. It is based on an x-ray-to-light converter, optical coupling, and a visible light detector. The converter screen, known as a scintillator, is deployed in both imaging and point detection, using either signal integration or counting. Two applications are explored in this review—sample examination and x-ray beam diagnostics for synchrotron sources. A large variety of scintillators are available to fulfill the needs of synchrotron applications. High dynamic range, small pixel size, and radiation hardness are the major advantages of scintillators. This article provides a review of the technical and scientific aspects of scintillators used in synchrotron radiation (i.e., storage rings and x-ray free-electron lasers). The advantages and drawbacks of implementation of the most popular scintillators on synchrotron beamlines are described.

Bioactive glasses and related bioactive glass-ceramics have been used for over three decades in biomedical applications such as bulk, particulate, or coatings materials. More recently, highly porous bioactive glass-ceramic scaffolds for bone-tissue engineering have also been developed from selected compositions of bioactive glasses. Current bioactive glass-ceramic scaffolds are characterized by an open porous network, high bioactivity, and mechanical properties similar to those of trabecular bone. This article reviews the latest achievements in the development of porous bioactive glass-ceramics intended for bone-tissue engineering applications, highlighting the fabrication technologies and scaffold properties. Improvements in the mechanical properties of bioactive glass-ceramic scaffolds exhibiting high bioactivity have been achieved by different approaches in the last 10 years. Relevant long-term in vivo studies are required to confirm the suitability of such bioactive glass-ceramic scaffolds in clinical applications.

Scanning tunneling microscopy (STM) is an excellent technique to image the surfaces of materials with extreme spatial resolution. However, it is difficult to maintain its imaging quality when applying the technique under the conditions used in many practical processes, such as chemical vapor deposition and catalysis. In this article, we describe two special classes of STM instruments that are capable of maintaining good imaging quality under “difficult” conditions, namely, one for high and variable temperatures and the other for the combination of high temperatures and high gas pressures. In both cases, we discuss the special design features that make these instruments robust with respect to the challenging imaging conditions and provide examples to illustrate how they are applied.

Hydrostatic pressure is an essential physical parameter for studying the structure, dynamics, phase behavior, and free-energy landscape of biomolecular systems. High pressure is an important feature of certain natural environments, and pressure effects on biosystems are of increasing interest for biotechnological applications. Here, we focus on the pressure-dependent activity of enzymes in different environments, from bulk solution to various interfaces. Results were obtained using a high-pressure stopped-flow methodology and high-pressure total internal reflection fluorescence spectroscopy. We highlight that pressure can enhance enzyme activity in various environments, contributing to the fundamental understanding of life under extreme conditions, and elucidate new ways to optimize biotechnological processes.

This article provides a personal guided tour of multiferroic materials, from their early days as a theoretical curiosity, to their position today as a focus of worldwide research activity poised to impact technology. The article begins with the history of, and the answer to, the question of why so few magnetic ferroelectric multiferroics exist, then gives a survey of the mechanisms and materials that support such multiferroicity. After discussing the tremendous progress that has been made in the magnetoelectric control of magnetic properties using an electric field, some unusual applications of multiferroics in high-energy physics and cosmology are outlined. Finally, the most interesting open questions and future research directions are addressed.

Structural DNA nanotechnology offers the capacity to construct ultraminiaturized devices with programmed nanoscale geometry, mechanical and dynamic properties, and site-specific molecular functionalities. These features and the possibility to position and orient molecules in user-defined ways may be exploited to create custom instruments for precision measurements of molecular-scale structure, dynamics, and interactions. Such devices may help constrain molecular motion along interesting reaction coordinates and may also exert forces to probe the mechanical properties or dynamics of molecules under study. Multiple ways of reading out device states may be used, including atomic force microscopy or transmission electron microscopy imaging, single-molecule or bulk fluorescence, or ionic conductivity as in nanopore systems. Early successes with custom scientific instruments based on DNA origami underline the tremendous potential to enable new approaches to making scientific discoveries in biological and synthetic materials systems.

Topological constraint theory is a convenient theoretical framework to predict structure–property relationships in glasses and identify optimal compositions featuring targeted macroscopic properties. Although introduced for chalcogenide glasses, molecular rigidity concepts have since been applied with great success to new families of materials, such as silicate glasses, phase-change materials, and proteins. Here, we review recent developments in the extension of rigidity theory to concrete, which is by far the most heavily manufactured material in the world. By capturing the important atomic topology while filtering out less relevant structural details of calcium–silicate–hydrate, the binding phase of concrete, topological constraint theory was used to nanoengineer concrete from the atomic scale by predicting the compositional dependence of hardness, toughness, and creep. As such, rigidity concepts represent a promising tool to accelerate the discovery of new materials with tailored properties.

The holy grail of regenerative technologies is to regrow a limb. This grand challenge requires us to develop truly innovative strategies and toolboxes across advanced materials science, stem cell science, physics, and developmental biology, and converge these advancements to address the limitations of wound healing and harness the regenerative capacity in humans. We discuss the convergence approach put forward by the field of regenerative engineering to develop translational strategies involving electrically conductive and novel polymers, stem cells, high-throughput technologies, and nanotechnology to regenerate the limb.

Crystallization in glasses is usually considered to be a problem in the glass industry. However, controlled crystallization of glasses is an important prerequisite in the development of glass-ceramics with tailored useful properties. Similar boundary conditions apply when considering glass-ceramics for the immobilization of nuclear waste via vitrification. While uncontrolled crystallization in nuclear-waste glasses is problematic, chemically durable glass-ceramics with significantly high waste loadings can be produced with controlled crystallization of glasses. This article presents an overview of various aspects of nuclear-waste glasses where crystallization is either considered to be advantageous or problematic. The classification of glass-ceramic waste forms and strategies to design glass-ceramics for a given waste stream is discussed. Some open and relevant problems faced by researchers developing nuclear-waste glass-ceramics are also offered.