A new concept of macroelectronics using assembled semiconductor nanowire thin films holds the promise of significant performance improvement. In this new concept, a thin film of oriented semiconductor nanowires is used to produce thin-film transistors (TFTs) with conducting channels formed by multiple parallel single-crystal nanowire paths. There fore, charges travel from source to drain within single crystals, ensuring high carrier mobility. Recent studies have shown that high-performance silicon nanowire TFTs and high-frequency circuits can be readily produced on a variety of substrates including glass and plastics using a solution assembly process. The device performance of these nanowire TFTs not only greatly surpasses that of solution-processed organic TFTs, but is also significantly better than that of conventional amorphous or polycrystalline silicon TFTs, approaching single-crystal silicon-based devices. Furthermore, with a similar frame-work, Group III-V or II-VI nanowire or nanoribbon materials of high intrinsic carrier mobility or optical functionality can be assembled into thin films on flexible substrates to enable new multifunctional electronics/optoelectronics that are not possible with traditional macroelectronics. This can have an impact on a broad range of existing applications, from flat-panel displays to image sensor arrays, and enable a new generation of flexible, wearable, or disposable electronics for computing, storage, and wireless communication.

Laser direct-write (LDW) is an established technology for manufacturing electronic and optoelectronic appliances such as cellular telephones, digital cameras, and notebook-type personal computers. One of the most successful applications is laser drilling of via holes on printed circuit boards for the manufacture of cellular telephones. Other practical applications include marking, dicing, trimming, repairing, patterning, bending, and rapid prototyping. In this article, the state of the art of LDW for industrial applications in Japan, the United States, and Europe is reviewed, and its future prospects are discussed.

Disordered, glassy materials are arguably one of the least understood states of condensed matter. Yet, they are ubiquitous in everyday life (polymers, “soft” glasses such as toothpaste, various emulsions, pastes, and foams) and in demanding applications (metallic glasses). Much of what is known about this important class of materials has been the result of truly concerted experimental and molecular modeling efforts. It is now generally accepted that amorphous materials exhibit dynamic and mechanical heterogeneities, but efforts to incorporate these into truly multiscale modeling approaches have been limited. This article describes the current state of affairs, along with many of the challenges that must be met to arrive at a fundamental understanding of amorphous materials and their response to external stresses.

This article reviews the state of the art in the field of porous amorphous metals by describing current processing techniques, mechanical properties, and potential applications. In addition to the reduction in density, the main benefit of introducing porosity in amorphous metals is the improvement in compressive ductility and energy absorption. This ductilizing effect is explained by: (1) shear-band interruption by individual pores at low porosities and (2) stable plastic bending of thin struts at higher porosities, with cellular amorphous metals displaying compressive ductilities of up to 80%.

The development of smart nanotextiles has the potential to revolutionize the functionality of our clothing and the fabrics in our surroundings. Nanoscale manipulation results in new functionalities for intelligent textiles, including self-cleaning, sensing, actuating, and communicating. This is made possible by such developments as new materials, fibers, and finishings; inherently conducting polymers; carbon nanotubes; and antimicrobial nanocoatings. These additional functionalities have numerous applications, encompassing healthcare, sports, military applications, and fashion. The wearer and the surrounding environment may be monitored in an innocuous manner, giving continuous updates of individual health status or environmental hazards. More generally, smart textiles become a critical part of the emerging area of body sensor networks incorporating sensing, actuation, control, and wireless data transmission. This article reviews current research in nanotechnology application to textiles, from fiber manipulation and development to end uses of smart nanotextiles.

Transparent conducting oxides (TCOs) are an increasingly important component of photovoltaic (PV) devices, where they act as electrode elements, structural templates, and diffusion barriers, and their work function controls the open-circuit device voltage. They are employed in applications that range from crystalline-Si heterojunction with intrinsic thin layer (HIT) cells to organic PV polymer solar cells. The desirable characteristics of TCO materials that are common to all PV technologies are similar to the requirements for TCOs for flat-panel display applications and include high optical transmissivity across a wide spectrum and low resistivity. Additionally, TCOs for terrestrial PV applications must use low-cost materials, and some may require device-technology-specific properties. We review the fundamentals of TCOs and the matrix of TCO properties and processing as they apply to current and future PV technologies.

Nature provides inspiration for enhanced control of adhesion through numerous examples ranging from geckos to jumping spiders. The primary strategy in these examples is the incorporation of patterns, specifically high-aspect-ratio topographic features, to ingeniously maximize adhesion forces while maintaining ease of release. Recently, considerable research efforts have been devoted toward the understanding, development, and optimization of synthetic analogues to these examples in nature. In this article, we provide insight into the mechanisms that lead to enhanced control of interfacial properties through patterning, the strategies that can be used for fabricating synthetic patterns, and an overview of experimental results that have been used to gain understanding and guidance in this emerging field.

Silicone polymers have become increasingly important as ingredients in skin care products, and the trend has accelerated over the last decade. While silicone compounds have existed since the 1860s, their increasing popularity in recent years is due in large part to a better understanding of their unique functions. This increased understanding of the properties of silicone, coupled with an increased ability of the silicone chemist to modify compounds, has resulted in more effective utilization of these materials in skin care formulations. Silicone polymers bring to formulations a phase that is soluble neither in oil nor in water. They are third-phase ingredients that when properly chosen can provide to formulations properties including surface-tension reduction, wetting, and emulsification.

Two-photon/multiphoton lithography (MPL) has emerged as a versatile technique for the fabrication of complex 3D polymeric, hybrid organic/inorganic, and metallic structures. This article reviews some recent advances in the development of molecules and materials that enable two-photon and multiphoton 3D micro- and nanofabrication. Materials that exhibit high sensitivity for the generation of reactive intermediates are described, as are various materials systems that enable functional devices to be made and in some cases enable structures to be replicated. The combination of advances illustrates the opportunities for MPL to have a significant impact in the areas of photonics, microelectromechanical systems, and biomedical technologies.

The remarkable electrical and thermal conductivities of isolated carbon nanotubes have spurred worldwide interest in using nanotubes to enhance polymer properties. Electrical conductivity in nanotube/polymer composites is well described by percolation, where the presence of an interconnected nanotube network corresponds to a dramatic increase in electrical conductivity ranging from 10−5 S/cm to 1 S/cm. Given the high aspect ratios and small diameters of carbon nanotubes, percolation thresholds are often reported below 1 wt% although nanotube dispersion and alignment strongly influence this value. Increases in thermal conductivity are modest (∼3 times) because the inter facial thermal re sis tance between nanotubes is considerable and the thermal conductivity of nanotubes is only 104 greater than the polymer, which forces the matrix to contribute more toward the composite thermal conductivity, as compared to the contrast in electrical conductivity, >1014. The nanotube network is also valuable for improving flame-retardant efficiency by producing a protective nanotube residue. In this ar ticle, we highlight published research results that elucidate fundamental structure–property relationships pertaining to electrical, thermal, and/or flammability properties in numerous nanotube-containing polymer composites, so that specific applications can be targeted for future commercial success.

X-ray absorption fine structure (XAFS) spectroscopy probes the structure and electronic properties of metal centers. Because it can be applied to noncrystalline materials, it is a key technique for probing nanoparticulate materials, such as colloidal and heterogeneous metal catalysts. The high brilliance of modern synchrotron radiation x-ray sources facilitates in situ studies, which provide direct structure–function relationships with both spatial and time resolution; this is especially effective when applied in combination with complementary techniques such as x-ray diffraction, mass spectrometry, and optical or vibrational spectroscopies. Tracking the particle formation of platinum-group metal catalysts, their behavior under reaction conditions, and the distribution of sites within a catalyst bed shows that this approach is essential for understanding the chemistry of these nanoparticles. Rather than behave as monolithic entities, nanoparticulate catalysts undergo rapid structural transformations induced by the gas environment and reaction conditions, and their lifetimes as catalysts depend on the reversibility of these changes.

Novel insect-foot–inspired materials may enable future robots to walk on surfaces regardless of the direction of gravity. Mini-Whegs™, a small robot that uses four wheel-legs for locomotion, was converted to a wall-walking robot with compliant, adhesive feet. First, the robot was tested with conventional adhesive feet. Then a new, reusable insect-inspired adhesive was tested on the robot. This structured polymer adhesive has less adhesive strength than conventional pressure-sensitive adhesives, but it has two important advantages: the foot material maintains its properties for more walking cycles before becoming contaminated, and the feet can then be washed and reused with similar results, which is not feasible with conventional adhesives. After the addition of a tail and widening the feet, the robot is capable of ascending vertical smooth glass surfaces using the structured polymer adhesive.

This article is based on the presentation given by Max G. Lagally (University of Wisconsin–Madison) as part of Symposium X: Frontiers of Materials Research on April 18, 2006, at the Materials Research Society Spring Meeting in San Francisco.

Structures with nanoscale dimensions are the essence of nanotechnology. Beginning with quantum dots and buckyballs, nanostructures now include nanotubes, rods, wires, and most recently, nanomembranes: very thin, large, freestanding or freefloating strain-engineered single crystals that can variously be made into tubes or other shapes, cut into millions of identical wires, or used as conformal sheets. This article provides a brief overview of the fabrication and properties of strained-silicon nanomembranes.

The following article is based on the Von Hippel Award address given by Knut W. Urban, chair of experimental physics at RWTH Aachen University and director of the Institute of Microstructure Research within the Department of Solid-State Research at the Jülich Research Center. Urban presented his award talk on November 29, 2006, during the 2006 Materials Research Society Fall Meeting in Boston. He was recognized with MRS's highest honor, the Von Hippel Award, for his “sustained contributions to the development and use of electron microscopy, and for major discoveries in the defect physics of quasicrystals and high-temperature superconductors.” The Von Hippel Award honors those qualities most prized by materials scientists and engineers—brilliance and originality of intellect, combined with vision that transcends the boundaries of conventional scientific disciplines, as exemplified by the life of Arthur von Hippel (http://vonhippel.mrs.org).

In this article, Urban describes the advances in spherical-aberration-corrected electron optics that have set transmission electron microscopy on an entirely new track in materials science. The new imaging theory for aberration-corrected instruments is based on exploiting both lens focus and spherical aberration as variable parameters to optimize contrast, resolution, and point spread. The novel negative-spherical-aberration imaging technique makes it possible to image low-nuclear-charge atoms, which were previously inaccessible directly by electron microscopy. This technique has proven particularly successful for research on oxides. Due to negligible point spread, quantitative measurements of atomic-site occupancies, which are equivalent to local concentrations, have become feasible. These improvements are dramatically expanding the potential of electron microscopy for quantitative studies in materials science.

The pipe organ is the king of musical instruments. No other instrument can compare with the pipe organ in power, timbre, dynamic range, tonal complexity, and sheer majesty of sound. The art of organ building reached its peak in the Baroque Age (∼1600–1750); with the industrial revolution in the 19th century, organ building shifted from a traditional artisans' work to factory production, changing the aesthetic concept and design of the organ so that the profound knowledge of the organ masters passed down over generations was lost.

This knowledge is being recreated via close collaborations between research scientists, musicians, and organ builders throughout Europe. Dozens of metallic samples taken from 17th- to 19th-century organ pipes have been investigated to determine their composition, microstructure, properties, and manufacturing processes using sophisticated methods of materials science. Based upon these data, technologies for casting, forming, hammering, rolling, filing, and annealing selected leadtin pipe alloys and brass components for reed pipes have been reinvented and customized to reproduce those from characteristic time periods and specific European regions. The new materials recreated in this way are currently being processed and used by organ builders for the restoration of period organs and the manufacture of new organs with true Baroque sound.

Bionanocomposites have established themselves as a promising class of hybrid materials derived from natural and synthetic biodegradable polymers and organic/inorganic fillers. Different chemistries and compositions can lead to applications from tissue engineering to load-bearing composites for bone reconstruction. A critical factor underlying biomedical nanocomposite properties is interaction between the chosen matrix and the filler. This ar ticle discusses current efforts and key research challenges in the development of these ma te rials for use in potential biomedical applications.