Polymer materials range from industrial commodities, such as plastic bags, to high-tech polymers used for optical applications, and all the way to biological systems, where the most prominent example is DNA. They can be crystalline, amorphous (glasses, melts, gels, rubber), or in solution. Polymers in the glassy state are standard materials for many applications (yogurt cups, compact discs, housings for technical equipment, etc.).

A photonic crystal is a periodically structured composite material, with a unit cell whose dimensions are of the order of an optical wavelength, made from constituents whose refractive indices differ greatly (Δn is of the order of 2). Three-dimensional (3D) photonic crystals typically consist of interpenetrating networks of dielectric material and air. Holographic lithography is a technology for the fabrication of photonic crystals in which the initial step is to define the 3D microstructure by interference of coherent light in a photosensitive precursor.

Sol-gel processing readily yields both inorganic and hybrid organic–inorganic materials. Commercial applications of solgel technology preceded the formal recognition of this technology as an important field of study. Likewise, successful commercial hybrid organic–inorganic polymers have been part of manufacturing technology since the 1950s.

It is not an overstatement to say that there would be no purpose in developing new materials unless due consideration were given to the load they exert on the global environment. The consumption of energy and other resources when a product is made, used, and returned should be minimized wherever possible.

As physical processes for generating miniaturized structures increase in resolution, the types of scientific questions one can ask and answer become increasingly refined. Indeed, if one had the capability to control surface architecture on the 1–100-nm length scale with reasonable speed and accuracy, one could ask and answer some of the most important questions in science and, in the process, develop technologies that could allow for major advances in surface science, chemistry, biology, and human health. This length scale, which is exceedingly difficult to control, comprises the length scale of much of chemistry and most of biology. Indeed, chemical and biochemical recognition events are essentially sophisticated examples of pattern-recognition processes. Therefore, if one could pattern on this length scale with control over feature size, shape, registration, and composition, one could systematically uncover the secrets of recognition processes involving extraordinarily complex molecules. Arecent invention, dip-pen nanolithography (DPN), may provide access to this type of control over surface architecture and entry into a new realm of structure-versus-function studies for chemists, biologists, physicists, and materials scientists.

Generally, when one looks up the properties of an element such as gold in an encyclopedia, one is immediately confronted with a list of established facts and figures. While many people are aware that most countries do not rely on a “gold reserve” anymore, it is surprising to learn that even basic physical and chemical properties of something as familiar as gold are not as fixed as one may believe. The reason for this is that tabulated values for material properties inevitably refer to macroscopic samples. It turns out that many simple properties such as those listed in the definition given here go spectacularly wrong as the size of the piece of gold is reduced. One of the most dramatic demonstrations of this was provided by Buffat and Borel, who measured the melting point of gold particles as a function of particle size using an electron microscope. They found that by the time gold crystals are just 4 nm across, the melting point drops to 700 K from its “encyclopedia value” of 1337 K. Another example is the noble character of gold metal.

Great progress in LSI (large-scale integration) has been made over the past 10 years, and more rapid progress is expected in the future. In recent years, the increased circuit density in LSI devices has led to remarkable heat generation, thereby creating thermalmanagement issues for microelectronics packaging. In order to develop highperformance LSI effectively, packaging and system-level configuration of the computer must be modified to handle the heat.

Because of large surface-to-volume ratios and low restoring forces, unwanted adhesion and friction can dominate the performance of microelectromechanical systems (MEMS) devices. To guarantee the function and reliability of MEMS devices, tribologists must understand the origins of adhesion, friction, and wear over a broad range of length scales from the macroscopic to the molecular. In this article, we present an overview of challenges, successes, and initial steps toward a fundamental understanding.

Mountains give the illusion of durability because their grand scale hides the continual weathering of their surfaces. When the same stone is used to create a sculpture, the loss of a few millimeters suffices to spoil, or even eliminate, the features of a face; the rate of loss may be surprising, but it is not necessarily unnatural.

The investigation of plutonium in glasses (amorphous ceramics lacking long-range order), in crystalline ceramics, and in composite materials composed of multiple crystalline or glass and crystalline phases, relieson multidisciplinary studies of physics, chemistry, and materials science. It involves the study of the plutonium atoms in materials with only short-range periodicity, as in glasses, to materials with long-range periodicity, as in crystals. The materials studied over the past 30 years include simple binary crystals, used to investigate the electronic structure of plutonium, to complex glasses and ceramics selected not only for the safety and durability that they provide for the immobilization of nuclear waste and plutonium, but also for the high flexibility they offer in composition. The lack of long-range order at the atomic level in glasses permits the inclusion of abroad range of waste elements, but it renders more difficult the interpretation of data from many commonly used experimental techniques. Regardless of the challenge, much of the research conducted in this field over the past few decades has been motivated by the use of plutonium as a surrogate for all nuclear-waste actinides or on its own in immobilization studies, in order to develop a durable glass or ceramic matrix that can resist leaching and mobilization of the plutonium on a geologic time scale.

Testing microelectromechanical systems (MEMS) includes testing a variety of electrical and mechanical signals. While powerful tools are available to test the electrical behavior of microfabricated systems, relatively few tools are available to measure micromechanical behavior.

Prior to receiving the Nobel Prize in chemistry in 2000 for my work in polymers, polymer science had been recognized three times. The first Nobel Prize in chemistry for polymer science was awarded in 1953 to Hermann Staudinger, for his pioneering work in the 1920s. At that time, the concept of macromolecules was new, and his ideas were controversial. However, the data prevailed, and he was awarded the Prize “for his discoveries in the field of macromolecular chemistry.” The next major event in polymer science was the discovery and invention of nylon by Wallace Carothers at the Dupont Company in 1935. Although Carothers died as a young man, his discoveries created an industry. I have little doubt that his work was deserving of a Nobel Prize and probably would have been awarded. The next related Prize went to Karl Ziegler and Giulio Natta in 1963 for their work on polymer synthesis in the 1950s. The Ziegler–Natta catalysts made possible the large-scale production of polymers such as polypropylene. They were awarded the Nobel Prize in chemistry “for their discoveries in the field of chemistry and technology of high polymers.” In 1974, the Prize for chemistry went to Paul J. Flory, who was a giant in this field. He was awarded the Nobel “for his fundamental achievements, both theoretical and experimental, in the physical chemistry of macromolecules.”

Considerable progress has been made in the study of environmental plutonium science in the last 30-plus years, driven to a large extent by concerns about the release and migration of large amounts of plutonium into the accessible geosphere. Plutonium has been introduced into the environment through several pathways. Environmental contamination has been caused by nuclear-weapons production and testing, nuclear-reactor accidents, and accidents during the transport of nuclear weapons. Above-ground testing of more than 420 nuclear weapons has produced large amounts of radionuclides through fission and neutron activation products. More than three metric tons of plutonium have been distributed on the earth's surface by global fallout. For example, the MAYAK plutonium production complex in the former Soviet Union is located in the southern Urals, about 70 km north of Chelyabinsk and 15 km east of Kyshtym. Between 1949 and 1951, about 76 million m3 of liquid radioactive waste with a total activity of 100 PBq (2.7 MCi) were discharged into the Techa River.

Impressive advances in vapor-phase deposition and photolithographic patterning techniques have been fueling the silicon microelectronics revolution over the last 40 years. However, for many interesting classes of materials, including biological materials or functional synthetic polymers, vacuum deposition and photolithography are not the techniques of choice for producing ordered structures and devices. Many of these materials selfassemble into well-ordered microstructures when deposited from solution, and patterning may be more readily achieved by solution-based selective deposition and direct-printing techniques. It is appealing to consider novel ways of manufacturing functional circuits and devices based on techniques that are similar to printing visual information onto paper.

Nanotechnology, a much abused term, refers to the fabrication and assembly of functional objects of nanometer dimensions. In this article, we will refer only to specific aspects of chemical nanotechnology, meaning by this the production of structures of nanometer dimensions by chemical means. In particular, we will center the discussion on the use of metal nanoparticles as chemical building blocks.

Over a decade ago, theorists predicted that photonic crystals active at visible and near-infrared wavelengths would possess a variety of exciting optical properties. Only in the last several years, however, have experimentalists begun to build materials that realize this potential in the laboratory. This lag between experiment and theory is primarily due to the to the challenges associated with fabricating these unique materials. As the term “crystal” suggests, these samples must consist of highly perfect ordered arrays of solids. However, unlike conventional crystals, which exhibit order on the angstrom length scale, photonic crystals must have order on the submicrometer length scale. In addition, many of the most valuable properties of photonic crystals are only realized when samples possess a “full” photonic bandgap. For such systems, large dielectric contrasts and particular crystal symmetries create a range of frequencies over which light cannot propagate. Realizing the nanoscopic architectures required to form such systems is a challenge for experimentalists. As a result, fabrication schemes that rely on lithographic techniques or spontaneous assembly have been a focus in the development of the field.