Recent developments in chemical synthesis, nanoscale assembly, and molecular-scale measurements enable the extension of the concept of macroscopic machines to the molecular and supramolecular levels. Molecular machines are capable of performing mechanical movements in response to external stimuli. They offer the potential to couple electrical or other forms of energy to mechanical action at the nano- and molecular scales. Working hierarchically and in concert, they can form actuators referred to as artificial muscles, in analogy to biological systems. We describe the principles behind driven motion and assembly at the molecular scale and recent advances in the field of molecular-level electromechanical machines, molecular motors, and artificial muscles. We discuss the challenges and successes in making these assemblies work cooperatively to function at larger scales.

Speed is the ultimate goal of racing, and materials are an increasingly important area of research for making race cars faster. The splitter, which produces front downforce, is made from Tegris, a polypropylene composite offering comparable stiffness and improved impact properties at significantly lower cost than alternative materials. Engine blocks must be cast iron, but careful control of microstructure using precision manufacturing methods produces a lighter engine block that generates more horsepower.

Speed and excitement must be balanced with safety, and materials are key players here, as well. Energy-dissipating foams in the car and the barriers surrounding the tracks allow drivers to walk away uninjured from accidents. Fire-resistant polymers protect drivers from high-temperature fuel fires, and technology transfer from the National Aeronautics and Space Administration (NASA) to the National Association for Stock Car Auto Racing (NASCAR) in the form of a low-temperature carbon monoxide catalyst filters the drivers' air.

Sports are an outstanding way of showing the public how materials science and engineering are relevant to their lives and interests. Materials science and engineering is just that much more exciting when it's traveling at two hundred miles an hour.

The renaissance of double tungstate (DW) and double molybdate (DMo) crystals is due to the vigorous recent progress in growth and characterization of these materials in the form of both bulk crystals with centimeter dimensions and epitaxial layers. “Double” refers to compounds having two ions with the generic composition MT(XO4)2 (where M = Li+, Na+, or K+; T = Ln3+, Y3+, or Bi3+; and X = W6+ or Mo6+). These compounds crystallize primarily in two phases belonging to the monoclinic (C2/c) and tetragonal (l4) structures. The specific properties of both types of crystals and the major technological challenges associated with the Czochralski and top-seeded solution growth of rare-earth doped crystals are presented. The performance of specific crystals is discussed in terms of their applications as tunable, thin-disk, and ultrashort (<100 fs) pulsed lasers or as nonlinear elements for laser Raman shifting.

Photonic crystals, in which the refractive index changes periodically, provide an exciting new tool for the manipulation of photons and have received keen interest from a variety of fields. This article reviews recent progress in the manipulation of photons by photonic crystals. First, the article covers spontaneous emission, a fundamental phenomenon associated with all photonic devices that emit light, which now can be successfully controlled. Light emission is suppressed in areas where the photonic crystal is complete, while strong emission occurs in the areas where there are artificial defects. Next, it is shown that a very strong confinement of photons in a small volume on the scale of cubic wavelengths becomes possible by using photonic crystals, where nanocavities with ultrahigh-Q values of more than 2 million have been successfully demonstrated. Finally, photonic crystals promise to realize unprecedented types of lasers, which can produce tailored beams on demand, while keeping stable single longitudinal and lateral modes.

Fundamental advances in solid-state ionics for energy conversion and storage are crucial in addressing the global challenge of cleaner energy sources. This review aims to demonstrate the valuable role that modern computational techniques now play in providing deeper fundamental insight into materials for solid oxide fuel cells and rechargeable lithium batteries. The scope of contemporary work is illustrated by studies on topical materials encompassing perovskite-type proton conductors, gallium oxides with tetrahedral moieties, apatite-type silicates, and lithium iron phosphates. Key fundamental properties are examined, including mechanisms of ion migration, dopant-defect association, and surface structures and crystal morphologies.

With the increasing demand for the development of nuclear power comes the responsibility to address the issue of waste, including the technical challenges of immobilizing high-level nuclear wastes in stable solid forms for interim storage or disposition in geologic repositories. The immobilization of high-level nuclear wastes has been an active area of research and development for over 50 years. Borosilicate glasses and complex ceramic composites have been developed to meet many technical challenges and current needs, although regulatory issues, which vary widely from country to country, have yet to be resolved. Cooperative international programs to develop advanced proliferation-resistant nuclear technologies to close the nuclear fuel cycle and increase the efficiency of nuclear energy production might create new separation waste streams that could demand new concepts and materials for nuclear waste immobilization. This article reviews the current state-of-the-art understanding regarding the materials science of glasses and ceramics for the immobilization of highlevel nuclear waste and excess nuclear materials and discusses approaches to address new waste streams.

Bending of thin sheets or ribbons is a ubiquitous phenomenon that impacts our daily lives, from the household thermostat to sensors in airbags. At nanometer-scale thicknesses, the mechanics responsible for bending and other distortions in sheets can be employed to create a nanofabrication approach leading to novel nanostructures. The process and resulting structures have been aptly referred to as “nanomechanical architecture.” In this article, we review recent progress in atomistic simulations that not only have helped to reveal the physical mechanisms underlying this nanofabrication approach, but also have made predictions of new nanostructures that can be created. The simulations demonstrate the importance of the atomic structure of the crystalline membrane and of the intrinsic surface stress in governing membrane bending behavior at the nanoscale and making the behavior fundamentally distinct from that at the macroscale. Molecular dynamics simulations of the bending of patterned graphene (a single-atomic layer film) suggest a new method for synthesizing carbon nanotubes with unprecedented control over their size and chirality.

Cantilever sensors have attracted considerable attention over the last decade because of their potential as a highly sensitive sensor platform for high throughput and multiplexed detection of proteins and nucleic acids. A micromachined cantilever platform integrates nanoscale science and microfabrication technology for the label-free detection of biological molecules, allowing miniaturization. Molecular adsorption, when restricted to a single side of a deformable cantilever beam, results in measurable bending of the cantilever. This nanoscale deflection is caused by a variation in the cantilever surface stress due to biomolecular interactions and can be measured by optical or electrical means, thereby reporting on the presence of biomolecules. Biological specificity in detection is typically achieved by immobilizing selective receptors or probe molecules on one side of the cantilever using surface functionalization processes. When target molecules are injected into the fluid bathing the cantilever, the cantilever bends as a function of the number of molecules bound to the probe molecules on its surface. Mass-produced, miniature silicon and silicon nitride microcantilever arrays offer a clear path to the development of miniature sensors with unprecedented sensitivity for biodetection applications, such as toxin detection, DNA hybridization, and selective detection of pathogens through immunological techniques. This article discusses applications of cantilever sensors in cancer diagnosis.

Shape-memory polymers (SMPs) offer a number of potential technical advantages that surpass other shape-memory materials such as shape-memory metallic alloys and shape-memory ceramics. The advantages include high recoverable strain (up to 400%), low density, ease of processing and the ability to tailor the recovery temperature, programmable and controllable recovery behavior, and more importantly, low cost. This article presents the state-of-the-art regarding SMPs. First, the architecture, type, and main properties of the traditional and recently developed SMPs are introduced. Second, structural and multifunctional SMP composites are summarized and discussed. These composites greatly enhance the performance of the SMPs and widen their potential applications. Finally, current applications of SMP materials in aerospace engineering, textiles, automobiles, and medicine are presented.

Semipolar InGaN/GaN quantum wells (QWs) are quite attractive as visible light emitters. One of the reasons is that a better optical transition probability is expected because of weaker internal electric fields, compared to conventional polar QWs. In addition, in-plane optical polarization anisotropy, which is absent in conventional QWs, is another relevant property because it affects device design and also may provide a means for novel applications. We revealed that the in-plane optical anisotropy in semipolar QWs switched from one direction perpendicular to the [0001] crystal axis to the perpendicular direction as the In composition increases. This is a property unique to semipolar QWs and enables, for example, to make cavity mirrors of laser diodes by cleavage. In this article, we describe the concept of semipolar planes and fabrication of high-quality epitaxial films for semipolar QWs. Furthermore, we discuss device fabrication and optical polarization anisotropy.

Research in n-channel field-effect transistors based upon III–V compound semiconductors has been very productive over the last 30 years, with successful applications in a variety of high-speed analog circuits. For digital applications, complementary circuits are desirable to minimize static power consumption. Hence, p-channel transistors are also needed. Unfortunately, hole mobilities are generally much lower than electron mobilities for III–V compounds. This article reviews the recent work to enhance hole mobilities in antimonide-based quantum wells. Epitaxial heterostructures have been grown with the channel material in 1–2% compressive strain. The strain modifies the valence band structure, resulting in hole mobilities as high as 1500 cm2/Vs. The next steps toward an ultra-low-power complementary metal oxide semiconductor technology will include development of a compatible insulator technology and integration of n- and p-channel transistors.

Reticular chemistry concerns the linking of molecular building blocks into predetermined structures using strong bonds. We have been working on creating and developing the conceptual and practical basis of this new area of research. As a result, new classes of crystalline porous materials have been designed and synthesized: metal-organic frameworks, zeolitic imidazolate frameworks, and covalent organic frameworks. Crystals of this type have exceptional surface areas (2,000−6,000 m2/g) and take up voluminous amounts of hydrogen (7.5 wt% at 77 K and 3−4 × 106 Pa), methane (50 wt% at 298 K and 2.5 × 106 Pa), and carbon dioxide (140 wt% at 298 K and 3 × 106 Pa). We have driven the basic science all the way to applications without losing sight of our quest for understanding the underlying molecular aspects of this chemistry. The presentation was focused on the design concepts, synthesis, and structure of these materials, with emphasis on their applications to onboard energy storage.

Turnbull performed much experimental and theoretical research on nucleation and on fundamental aspects of phase transformations in condensed matter. Nucleation of precipitates followed in parallel or sequentially by their growth and coarsening is a complex scientific subject and technologically highly relevant because of the many critical roles played by structural metallic alloys and their relevance to the energy problem. The focus herein is on nucleation, growth, and coarsening of precipitates employing atom-probe tomography, lattice kinetic Monte Carlo simulations, and diffusion theory, which constitute a unique approach for studying phase separation in concentrated multicomponent alloys.

Relaxor-based single crystals of complex perovskite solid solutions, Pb(Mg1/3Nb2/3)O3–PbTiO3 [PMN–PT] and Pb(Zn1/3Nb2/3)O3–PbTiO3 [PZN–PT], exhibit extraordinary piezoelectric performance, with extremely high piezoelectric coefficients, very large electromechanical coupling factors, and exceptionally high strain levels. These materials outperform the currently used Pb(Zr1–xTix)O3 [PZT] ceramics, making them the materials of choice for the next generation of electromechanical transducers for a broad range of advanced applications. In this article, recent major advances in the development of piezocrystals are reviewed in terms of crystal growth, piezoelectric properties, crystal chemistry, domain structure, and device applications.

During the past decade, the electrochemical properties (energy density, power capability, and cycling stability) of practical lithium (Li) batteries have been enormously improved. Surprisingly, although the knowledge exists of how to prepare excellent batteries, a detailed understanding of how they actually work is still lacking. In particular, the impact of interfaces in electrode composites is poorly understood. Here, we collect the most advanced mechanistic studies performed in our laboratory or published in recent literature and try to embed this knowledge into the well-established concepts used in solid-state ionics for many decades. In particular, we focus on the so-called perpendicular and parallel interfacial effects. We show that much of the old wisdom can be applied to batteries, although there are several important differences. We discuss, in some detail, the effects of charge incorporation, electronic interphase contacting, electrode porosity, and heterogeneous doping in selected advanced electrode materials and emphasize the future perspectives.