When MRS Bulletin published its expanded special issue in April 2008, “Harnessing Materials for Energy,” it was not a project done lightly. The impetus for this effort was the desire to describe the veritable options that materials provide in energy technologies. These options can then be evaluated in the context of other imperatives such as economic viability and environmental concerns, which all interact to determine societal choices for energy.

Improved battery technology, innovative recharging strategies, and generous financial incentives are making electric vehicles more attractive to consumers than ever before.

Tata is a household name in India. Starting well over a century ago, the Tatas began their foray into industry, and the brand represents more than a diversifed conglomerate. The Tatas are well-respected, having endeared themselves in every walk of Indian life. Their businesses are all-pervasive, from building automobiles and generating electric power to making steel and building supercomputers. Their charitable trusts and endowments are as extensive as their businesses. They have founded and funded outstanding educational institutions and human welfare organizations, and they have supported research on alleviating human suffering. The incumbent of the Tata Group is Ratan Naval Tata, a Cornell University graduate in architecture. In the 20 years since he took over the mantle, he has set the Tata industries on a steep growth trajectory, increasing the revenue of the Tata industries 12-fold, making automobiles—the famed Nano—available at very affordable prices in India, and introducing effcient steelmaking. The business empire he heads, the Tata Group, has over 90 companies with footholds in 80 countries. In the midst of his busy globe-trotting schedule, we managed to steal an hour of his time at the Tatas' “Bombay House” headquarters for him to tell us how he sees the global energy challenges and the opportunities they create.

If you had to guess which country produces the most electrical power from photovoltaics (PV), you would probably draw candidates from sunny places such as the Middle East, the Mediterranean, or the United States. Germany, with its gray northern European skies, seems an unlikely contender.

Responsive materials cover a breadth of types and many application fields. The common feature in all cases is a nonlinear change in properties or behavior as a result of a stimulus. The material response can range from a simple change in conformation or ionization state, through to phase transitions, bulk aggregation, or complete dissolution. As a consequence, sensing and actuation are the most investigated functions of these materials. In this issue, we have chosen to focus on responsive materials as exemplified by externally switchable, environmentally activated, and reversibly or controllably triggered systems. The chemistries of these materials, their physical properties, functional behavior, and activity are all linked, so we have aimed to cover the many disciplines underlying responsive materials through articles featuring areas that already span disparate research topics. These areas include drug delivery, smart surfaces, and nanotube transducers. The responsive materials field is growing in excitement as well as activity, and we hope that readers will gain an insight into this fascinating branch of materials science through this MRS Bulletin issue.

Extensive research activity is currently devoted to controlled drug delivery systems, mainly as nano-sized particles. Although biocompatible and (bio)degradable polymers play a key role in this field, their shaping into colloidal particles (e.g., polymeric micelles and nanoparticles) usually requires the proper design of amphiphilic copolymers as effective stabilizers. Strategies for synthesizing these copolymers that preserve the intrinsic properties of the constitutive polymers are discussed in this article. Synthesis of amphiphilic copolymers with a more complex structure and endowed with functionality is also considered, with the purpose of enhancing the performance of the nanocarriers. The focus is increasingly on nanocarriers of the third generation, which resist coalescence and elimination by the immune system, and which are readily incorporated into chosen target cells. The more recent quest is for smart nanocarriers that exhibit the additional capacity of being stimuli-responsive.

Much of the interaction of a material with its environment is governed by its surface, and modulation of the material's surface characteristics can vastly broaden its range of application. This review focuses on the tailoring of surfaces of materials to achieve specific changes in their responses to external stimuli to enhance their prospects for applications in the biomedical field. Combining the inherent properties of different classes of materials such as polymers, metals, mesoporous materials, and magnetic nanoparticles with a responsive surface presents unique opportunities. Applications include surface-modified filters for the effective adsorption and separation of biomolecules, materials for the promotion of cell adhesion or detachment for cell sheet engineering and regenerative medicine, actuators, or valves, and vehicles for the controlled and targeted delivery of therapeutic agents. The commonly used external stimuli are heat, pH, and light, and these, as well as electrical stimulation used in conjunction with conducting polymers, will be addressed in this review. Progress in the field of responsive surfaces has been rapid, and continuing research can be expected to result in more innovative and exciting developments. Nevertheless, much work remains to be done to meet the challenges in the translation of these systems from the laboratory to clinical applications.

Individual nanotubes made of carbon, boron nitride, iron, silicon, or other materials have properties such as high strength, toughness, electrical and thermal conductivity, and light weight that cannot be matched by conventional materials. Nanotubes also change their properties in response to external fields and change one type of energy into another, which are useful for design. This article explores three main steps in exploiting responsive materials based on nanotubes: nanotube synthesis, macroscale material fabrication, and incorporation into device structures for novel applications. Nanotubes are always synthesized as individual particles in the form of powders, smoke particles, or aligned forests. To be industrially important, nanotubes generally must be processed to form derivative materials such as functionalized/coated powders and forests and macroscale intermediate materials such as sheets, ribbon, and yarn. The processed nanotubes are then used to develop responsive materials and devices that are able to resist, react to, or generate energy from their environment. This article provides background information and ideas on how to develop nanotube responsive materials for everyday use.

The idea of first-principles methods is to determine the properties of materials by solving the basic equations of quantum mechanics and statistical mechanics. With such an approach, one can, in principle, predict the behavior of novel materials without the need to synthesize them and create a virtual design laboratory. By showing several examples of new electrode materials that have been computationally designed, synthesized, and tested, the impact of first-principles methods in the field of Li battery electrode materials will be demonstrated. A significant advantage of computational property prediction is its scalability, which is currently being implemented into the Materials Genome Project at the Massachusetts Institute of Technology. Using a high-throughput computational environment, coupled to a database of all known inorganic materials, basic information on all known inorganic materials and a large number of novel “designed” materials is being computed. Scalability of high-throughput computing can easily be extended to reach across the complete universe of inorganic compounds, although challenges need to be overcome to further enable the impact of first-principles methods.

Soft matter—also known as complex fluids—is a field of growing interest and importance, spanning many classes of materials, including polymers, biopolymers, colloids, and liquid crystals. Different approaches for microstructural characterization are more appropriate than those used for hard (and usually fully crystallized) materials such as metals and inorganic materials because of the time and length scales involved. This article discusses a range of techniques applicable to the characterization of soft matter, including environmental scanning electron microscopy (SEM) and microrheology. The former offers two key advantages for this class of material over conventional SEM because it requires neither a high vacuum—which is a problem for hydrated samples—nor that an insulator be coated with a conductive material. Microrheology is well suited to small volumes of fluid with low moduli that may be heterogeneous; it is capable of measuring gelation in real time.