This issue contains assessments of battery performance involving complex, interrelated physical and chemical processes between electrode materials and electrolytes. Transformational changes in battery technologies are critically needed to enable the effective use of renewable energy sources such as solar and wind to allow for the expansion of hybrid electric vehicles (HEVs) to plug-in HEVs and pure-electric vehicles. For these applications, batteries must store more energy per unit volume and weight, and they must be capable of undergoing many thousands of charge-discharge cycles. The articles in this theme issue present details of several growing interest areas, including high-energy cathode and anode materials for rechargeable Li-ion batteries and challenges of Li metal as an anode material for Li batteries. They also address the recent progress in systems beyond Li ion, including Li-S and Li-air batteries, which represent possible next-generation batteries for electrical vehicles. One article reviews the recent understanding and new strategies and materials for rechargeable Mg batteries. The knowledge presented in these articles is anticipated to catalyze the design of new multifunctional materials that can be tailored to provide the optimal performance required for future electrical energy storage applications.

Nanotechnology has had a huge impact on the development of therapeutics over the last couple of decades. To date, a large number of organic nanoparticles have been developed to encapsulate and deliver therapeutic and imaging agents. These nanoparticles have allowed encapsulation and targeted release of drugs. A few nanoparticle-based drugs are already being used in patients, and several others are making excellent progress toward clinical translation. The strong pipeline of therapeutic nanoparticles is fueled by advances in novel materials and design features, new applications, and a better understanding of fundamental hurdles that limit the utility of nanoparticles. The articles in this issue of MRS Bulletin are focused on some of the significant recent advances in the use of organic nanoparticles for drug delivery and imaging.

Organic materials provide a unique platform for exploiting the spin of the electron—a field dubbed organic spintronics. Originally, this was mostly motivated by the notion that because of weak spin-orbit coupling, due to the small mass elements in organics and small hyperfine field coupling, organic matter typically displays a very long electron spin coherence time. More recently, however, it was found that organics provide a special class of spintronic materials for many other reasons—several of which are discussed throughout this issue. Over the past decade, there has been a growing interest in utilizing the molecular spin state as a quantum of information, aiming to develop multifunctional molecular spintronics for memory, sensing, and logic applications. The aim of this issue is to stimulate the interest of researchers by bringing to their attention the vast possibilities not only for unexpected science but also for the enormous potential for developing new functionalities and applications. The six articles in this issue deal with some of the breakthrough work that has been ongoing in this field in recent years.

Water is, perhaps, the most important material known to humankind—fascinating even in its pure state for the range of anomalous properties it displays. There has been an increasing realization that understanding the behavior of water at interfaces—from those of small solutes to biomolecules and polymers to inorganic materials and metals—holds the key to understanding disparate phenomena, from self-assembly, biofouling, and catalysis to corrosion. In this issue of MRS Bulletin, we highlight recent advances in understanding the molecular behavior of water near a range of interfaces of interest to the broader materials community.

It is well established that symmetry has an important influence on the properties of materials, but the topology of electronic states might be an even more fundamental property. Topological insulators (TIs) are new states of matter based on the topology in the electronic band structure. Relativistic effects are the origin of the topologically non-trivial electronic structure, and the new state of matter has been realized in two-dimensional quantum well structures and three-dimensional bulk crystals of heavy elements and compounds. TI materials have an insulating gap in the bulk, and robust metallic edge/surface states on the boundary, which is robust against disorder and leads to unique spin and charge transport properties. Examples of TIs include HgTe/CdTe quantum wells, Bi-Sb-alloys, Bi2Se3, and half-Heusler compounds.

“Smaller is stronger.” Nanostructured materials such as thin films, nanowires, nanoparticles, bulk nanocomposites, and atomic sheets can withstand non-hydrostatic (e.g., tensile or shear) stresses up to a significant fraction of their ideal strength without inelastic relaxation by plasticity or fracture. Large elastic strains, up to ∼10%, can be generated by epitaxy or by external loading on small-volume or bulk-scale nanomaterials and can be spatially homogeneous or inhomogeneous. This leads to new possibilities for tuning the physical and chemical properties of a material, such as electronic, optical, magnetic, phononic, and catalytic properties, by varying the six-dimensional elastic strain as continuous variables. By controlling the elastic strain field statically or dynamically, a much larger parameter space opens up for optimizing the functional properties of materials, which gives new meaning to Richard Feynman’s 1959 statement, “there’s plenty of room at the bottom.”

It is now widely recognized that continued performance gains in electronic computing will require new materials, both in the short and long term. In the short term, the silicon channel in transistors will be replaced by materials with higher mobility that are easier to “scale” (make thinner). In data storage, the goal is to have fast, non-volatile memory with a smaller cell size. In the long term, new architectures and new types of logic devices will be needed in order to further reduce power consumption. New materials cannot only boost performance, but can also add new functionalities, such as on-chip photonics, which can vastly improve interchip interconnects. The need for new materials is a big opportunity for materials research, but also a challenge. Replacement technologies must outperform conventional silicon technology, but also be compatible with the vast infrastructure of silicon manufacturing. Examples of some of the materials advances in the areas of computation, memory, and communication are given in this issue of MRS Bulletin.

Solid-oxide fuel cells (SOFCs) are unique in their ability to directly convert the chemical energy of a wide variety of fuels to electric power with unmatched energy conversion efficiency. The articles in this issue of MRS Bulletin highlight the enormous potential of, and recent progress toward, operating SOFCs at lower temperatures (<650°C). Lower temperatures dramatically increase the number of potential applications for this technology as well as provide the opportunity to incorporate a wider variety of materials in SOFC power generation systems with greater reliability and lower cost. The articles in this issue describe materials development and processing for low-temperature SOFCs, including the enabling of nanotechnology and microelectromechanical systems-based cell designs, the development of highly active electrodes and their three-dimensional microstructural characterization, as well as the use of novel proton-conducting electrolytes, all of which provide new avenues of research. New fabrication methods are also being applied in the development of micro-SOFCs and microtubular SOFCs with higher power densities. Finally, advances in lowering performance degradation rates, a critical commercialization issue, are described.

Biological cells are major building blocks of tissues and organs of living organisms. These cells are also being used as biomarkers for diagnosis and sources for regenerative medicine. To better understand and even regulate diverse activities of cells, materials capable of interacting with cells have been designed by integrating various material chemistry, characterization, and processing techniques. These materials are often integrated with various nano- and microscale engineering devices. In this article, we provide an overview of materials for biological modulation, sensing, and imaging and also discuss opportunities for the future development of multifunctional materials for sensing and therapies.

The biological effects of engineered nanoparticles are presently a focus of interest in chemistry, biology, pharmacology, clinical medicine, and toxicology due to the enormous therapeutic and diagnostic potential that the particulate nature of nanoparticles offers for selective drug delivery and controlled release. This raises unprecedented safety issues, calling for novel paradigms to face the biocompatibility analysis of particulate (as opposed to molecular) bioactive agents that vary in shape, surface, and charge, in addition to chemical structure. This issue of MRS Bulletin focuses on the bioeffects of metal oxide nanostructures, whose high bioactivity can be exploited to design novel multifunctional devices for nanomedical applications, some of which are already undergoing testing in anticancer and antioxidant clinical trials. The ubiquitous application in research and technology of these non-biodegradable structures has evoked concerns regarding their potential hazards, due to the same chemical activities that promise nanomedical developments. A Janus-type scenario is emerging, pointing to intricate networks of beneficial and detrimental effects following the biological interactions of metal oxide nanoparticles.

Focused ion beam microscopes are extremely versatile and powerful instruments for materials research. These microscopes, when coupled in a system with a scanning electron microscope, offer the opportunity for novel sample imaging, sectioning, specimen preparation, three-dimensional (3D) nano- to macroscale tomography, and high resolution rapid prototyping. The ability to characterize and create materials features in a site-specific manner at nanoscale resolution has provided key insights into many materials systems. The advent of novel instrumentation, such as new ion sources that encompass more and more of the periodic table, in situ test harnesses such as cryogenic sample holders for sensitive material analyses, novel detector configurations for 3D structural, chemical, and ion contrast characterization, and robust and versatile process automation capabilities, is an exciting development for many fields of materials research.

Diamond is a unique material that often exhibits extreme properties compared to other materials. Discovered about 30 years ago, the use of hydrogen in plasma-enhanced chemical vapor deposition (CVD) has enabled the growth and coating of diamond in film form on various substrate materials. CVD diamond research has been actively continued subsequently to develop new understanding and approaches for the growth and processing of this fascinating material. Currently, the study and development of diamond films has enabled a wide range of applications based on the combination of unique and extreme properties of diamond and the variety of film properties obtainable through tuning the microstructure, morphology, impurities, and surfaces. This issue of MRS Bulletin introduces the latest research, recent applications, and the challenges ahead for CVD diamond films.