bluuebunny/crossref_metadata_2025 huggingface dataset:
Gene Delivery by Immobilization to Cell-Adhesive Substrates
Authors: Bengali Zain , Shea Lonnie D.
Published: February 2011

Biomaterials can potentially enhance the delivery of viral and nonviral vectors for both basic science and clinical applications.Vectors typically consist of nucleic acids (DNA, RNA) packaged with proteins, lipids, or cationic polymers, which facilitate cellular internalization and trafficking. These vectors can associate with biomaterials that support cell adhesion, a process we term substrate-mediated delivery. Substrate immobilization localizes the DNA and the delivery vector to the cellular microenvironment.The interaction between the vector and substrate must be appropriately balanced to mediate immobilization, yet allow for cellular internalization. Balancing the binding between the biomaterial and the vector is dependent upon the surface chemistries of the material and the vector, which can be designed to provide both specific (e.g., biotin–avidin, the strongest known noncovalent interaction between a protein and its ligand) and nonspecific (e.g., van der Waals) interactions. In this review, we describe the biomaterial and vector properties that mediate binding and gene transfer, identify potential applications, and present opportunities for further development.
Peptide-Enhanced Nucleic Acid Delivery
Authors: Bergen Jamie M. , Pun Suzie H.
Published: February 2011

Numerous barriers, both extracellular and intracellular, hinder successful and efficient nonviral nucleic acid delivery. Due to their small size and ability to specifically recognize and interact with molecular targets, peptides can be incorporated as modular elements into synthetic nucleic acid delivery systems to overcome many of these barriers. Three classes of peptides that have frequently been integrated as components in nucleic acid delivery systems include cell-penetrating peptides (CPPs), endosomal release peptides, and nuclear localization sequences (NLSs).Various additional classes of peptides show promise for enhancing nucleic acid delivery by targeting cell surface receptors, inhibiting nuclease activity, and directing nucleic acids toward intracellular targets. In addition to a review of the various existing approaches to peptide-enhanced nucleic acid delivery, this article will discuss strategies for the development of new peptides and approaches for the incorporation of these peptides into nucleic acid delivery systems.
Self-Assembly in Materials Synthesis
Authors: Tirrell Matthew V. , Katz Alexander
Published: February 2011

The synthesis of materials via self-assembly typically involves the spontaneous and reversible organization of small building blocks for the purpose of creating conglomerate structures over larger length scales. This introductory article describes self-assembly processes on several length scales, from subnanometer up to millimeter scales, and briefly summarizes some of the incredible diversity of materials that exhibit selfassembly. Articles in this issue cover self-assembly using zeolitic structures, organic molecular crystals, block copolymers, surfactants, mesoscale templates, and soluble crystallization additives. Keywords: block copolymers, materials synthesis, self-assembly, surfactants, templates, zeolites.
Biomimetic Mineralization/Synthesis of Mesoscale Order in Hybrid Inorganic–Organic Materials via Nanoparticle Self-Assembly
Authors: Cölfen Helmut , Yu Shu-Hong
Published: February 2011

The organization of nanostructures across several length scales by self-assembly is a key challenge in the design of advanced materials. In meeting this challenge, materials scientists can learn much from biomineralization processes in nature. These processes result in hybrid inorganic–organic materials with exquisite and optimized properties, complex forms, and hierarchical order over extended length scales.

Biominerals are usually produced in the presence of an insoluble organic template as well as soluble molecules, which control inorganic crystallization, growth, and selfassembly. These processes can be mimicked successfully, resulting in inorganic–organic hybrid materials with complex form and mesoscale order via a nanoparticle selfassembly process.Various strategies can be applied, including the balancing of aggregation and crystallization, transforming and reorganizing of pre-formed nanoparticle building blocks, and face-selective coding of nanoparticle surfaces by additives for controlled self-assembly. The underlying principles of biomimetic mineralization will be described, along with selected examples showing that while much has already been achieved, the perfection of natural systems is still out of reach.
Nanopatterning with UV Optical Lithography
Authors: Rothschild M. , Bloomstein T. M. , Efremow N. , Fedynyshyn T. H. , Fritze M. , Pottebaum I. , Switkes M.
Published: February 2011

Optical lithography at ultraviolet (UV) wavelengths is the standard process for patterning 90-nm state-of-the-art devices in the semiconductor industry, and extensions to 45 nm and below are currently being explored. With such high resolution, the inherent high throughput of optical lithography will enable the development of a broad range of applications beyond semiconductor electronics. In this article, we will review progress toward nanopatterning with UV light in a variety of materials and geometries.The common thread is the use of short wavelengths, 193 nm or 157 nm, coupled with immersion to further reduce the effective wavelength. Densely spaced, 32-nm (and even smaller) features have been patterned, facilitating the future preparation of large-area, deeply scaled microelectronics, nanophotonics, nanobiology, and molecular-scale self-assembly.
Block Copolymer Lithography: Merging “Bottom-Up” with “Top-Down” Processes
Authors: Hawker Craig J. , Russell Thomas P.
Published: February 2011

As the size scale of device features becomes ever smaller, conventional lithographic processes become increasingly more difficult and expensive, especially at a minimum feature size of less than 45 nm. Consequently, to achieve higher-density circuits, storage devices, or displays, it is evident that alternative routes need to be developed to circumvent both cost and manufacturing issues.

An ideal process would be compatible with existing technological processes and manufacturing techniques; these strategies, together with novel materials, could allow significant advances to be made in meeting both short-term and long-term demands for higher-density, faster devices. The self-assembly of block copolymers (BCPs), two polymer chains covalently linked together at one end, provides a robust solution to these challenges. As thin films, immiscible BCPs self-assemble into a range of highly ordered morphologies where the size scale of the features is only limited by the size of the polymer chains and are, therefore, nanoscopic.

While self-assembly alone is sufficient for a number of applications in fabricating advanced microelectronics, directed, self-orienting, self-assembly processes are also required to produce complex devices with the required density and addressability of elements to meet future demands. Both strategies require the design and synthesis of polymers that have well-defined characteristics such that the necessary fine control over the morphology, interfacial properties, and simplicity of processes can be realized. By combining tailored self-assembly processes (a “bottom-up” approach) with microfabrication processes (a “top-down” approach), the ever-present thirst of the consumer for faster, better, and cheaper devices can be met in very simple, yet robust, ways. The integration of novel chemistries with the manipulation of self-assembly will be treated in this article.
Quantum Information
Authors: Davidovich Luiz
Published: February 2011

The following article is based on the plenary address by Luiz Davidovich (Federal University of Rio de Janeiro), presented on April 14, 2004, at the 2004 MRS Spring Meeting in San Francisco. The field of quantum information is a discipline that aims to investigate methods for characterizing, transmitting, storing, compressing, and computationally utilizing the information carried by quantum states. It owes its rapid development over the last few years to several factors: the ability, developed in several laboratories, to control and measure simple microscopic systems; the discovery of fast quantum algorithms; and the recognition that Moore's law will soon lead to the single-atom limit of elementary computing gates.Cryptography and quantum computing are among the main applications in the field.They rely on the subtle and fundamental properties of the quantum world: the unavoidable disturbance associated with measurement, the superposition principle, and the nonlocal properties of entangled states. Progress in this area is intimately connected to a deep understanding of quantum physics: recent achievements include the experimental demonstration of teleportation and detailed investigations of the role of the environment in the quantum–classical transition. This article reviews basic concepts and recent developments in the field of quantum information, emphasizing the close ties between fundamental research and possible applications.
Microengineering the Environment of Mammalian Cells in Culture
Authors: Chen Christopher S. , Jiang Xingyu , Whitesides George M.
Published: February 2011

Assays based on observations of the biological responses of individual cells to their environment have the potential to make enormous contributions to cell biology and biomedicine.To carry out well-defined experiments using cells, both the environments in which the cells live and the cells themselves must be well defined. Cell-based assays are now plagued by inconsistencies and irreproducibility, and a primary challenge in the development of informative assays is to understand the fundamental bases for these inconsistencies and to limit them. It now seems that multiple factors may contribute to the variability in the response of individual cells to stimuli; some of these factors may be extrinsic to the cells, some intrinsic. New techniques based on microengineering—especially using soft lithography to pattern surfaces at the molecular level and to fabricate microfluidic systems—have provided new capabilities to address the extrinsic factors. This review discusses recent advances in materials science that provide well-defined physical environments that can be used to study cells, both individually and in groups, in attached culture. It also reviews the challenges that must be addressed in order to make cell-based assays reproducible.
Investigating the Function of Ion Channels in Tethered Lipid Membranes by Impedance Spectroscopy
Authors: Terrettaz Samuel , Vogel Horst
Published: February 2011

The function of biologically important ion channels can be measured in supported lipid membranes by impedance spectroscopy. This approach offers substantial advantages over traditional electrophysiological measurements. In this article, we present an overview of the field, with a special emphasis on the reconstitution of ion channels in lipid bilayers tethered to gold electrodes and the modulation of their channel activity by specific ligand binding.
Polymer–Fullerene Bulk Heterojunction Solar Cells
Authors: Janssen René A. J. , Hummelen Jan C. , Sariciftci N. Serdar
Published: February 2011

Nanostructured phase-separated blends, or bulk heterojunctions, of conjugated polymers and fullerene derivatives form a very attractive approach to large-area, solid-state organic solar cells. The key feature of these cells is that they combine easy processing from solution on a variety of substrates with good performance. Efficiencies of up to 5% in solar light have been achieved, and lifetimes are increasing to thousands of hours. Further improvements can be expected and some of the promising strategies towards that goal are presented in this article.
Degradation of SiC High-Voltage pin Diodes
Authors: Ha Seoyong , Bergman J. P.
Published: February 2011

The recent discovery of forward-voltage degradation in SiC pin diodes has created an obstacle to the successful commercialization of SiC bipolar power devices. Accordingly, it has attracted intense interest around the world. This article summarizes the progress in both the fundamental understanding of the problem and its elimination.The degradation is due to the formation of Shockley-type stacking faults in the drift layer, which occurs through glide of bounding partial dislocations. The faults gradually cover the diode area, impeding current flow. Since the minimization of stress in the device structure could not prevent this phenomenon, its driving force appears to be intrinsic to the material. Stable devices can be fabricated by eliminating the nucleation sites, namely, dissociated basal-plane dislocations in the drift layer.Their density can be reduced by the conversion of basal-plane dislocations propagating from the substrate into threading dislocations during homoepitaxy.
Triblock Copolymer as an Effective Membrane-Sealing Material
Authors: Wu Guohui , Frey Shelli L. , Maskarinec Stacey A. , Lee Ka Yee C.
Published: February 2011

An intact cell membrane serves as a permeable barrier, regulating the influx and efflux of ions and small molecules. When the integrity of the membrane is compromised, its barrier function is also disrupted, threatening the survival of the cell. Triblock copolymer surfactants of the form poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) have been shown to help seal structurally damaged membranes, arresting the leakage of intracellular materials.

In order to understand how this particular family of triblock copolymers helps seal damaged membranes, model lipid monolayer and bilayer systems have been used to unravel the nature of the lipid/copolymer interaction. The copolymer surfactant is found to selectively insert into structurally compromised membranes, thus localizing its sealing effect on the damaged regions. The inserted polymer is “squeezed out” when the lipid packing density is increased, suggesting a mechanism for the cell to be rid of the polymer when the membrane integrity is restored.
Ultrafast Lasers in Materials Research
Authors: Cahill David G. , Yalisove Steve M.
Published: February 2011

With the availability of off-the-shelf commercial ultrafast lasers, a small revolution in materials research is underway, as it is now possible to use these tools without being an expert in the development of the tools themselves. Lasers with short-duration optical pulses—in the sub-picosecond (less than one-trillionth of a second) range—are finding a variety of applications, from basic research on fast processes in materials to new methods for microfabrication by direct writing. A huge range of pulse energies are being used in these applications, from less than 1 nJ (a billionth of a joule) to many joules.
Silicon Surface Morphologies after Femtosecond Laser Irradiation
Authors: Tull Brian R. , Carey James E. , Mazur Eric , McDonald Joel P. , Yalisove Steven M.
Published: February 2011

In this article, we present summaries of the evolution of surface morphology resulting from the irradiation of single-crystal silicon with femtosecond laser pulses. In the first section, we discuss the development of micrometer-sized cones on a silicon surface irradiated with hundreds of femtosecond laser pulses in the presence of sulfur hexafluoride and other gases. We propose a general formation mechanism for the surface spikes. In the second section, we discuss the formation of blisters or bubbles at the interface between a thermal silicon oxide and a silicon surface after irradiation with one or more femtosecond laser pulses. We discuss the physical mechanism for blister formation and its potential use as channels in microfluidic devices.
Density Functional Theory in Surface Science and Heterogeneous Catalysis
Authors: Nørskov J.K. , Scheffler M. , Toulhoat H.
Published: February 2011

Solid surfaces are used extensively as catalysts throughout the chemical industry, in the energy sector, and in environmental protection. Recently, density functional theory has started providing new insight into the atomic-scale mechanisms of heterogeneous catalysis, helping to interpret the large amount of experimental data gathered during the last decades. This article shows how density functional theory can be used to describe the state of the surface during reactions and the rate of catalytic reactions. It will also show how we are beginning to understand the variation in catalytic activity from one transition metal to the next. Finally, the prospects of using calculations to guide the development of new catalysts in industry will be discussed.
Polymer Membranes for Hydrogen Separations
Authors: Perry John D. , Nagai Kazukiyo , Koros William J.
Published: February 2011

The development of a hydrogen-based economy would generate a substantial necessity for efficient means of collecting hydrogen with a relatively high purity. Membrane separations play a major role in the separation of hydrogen gas from various gas mixtures, and this article discusses the use of polymeric materials to produce these membranes. After a review of the historical use of polymeric membranes and some background information regarding mechanisms of gas transport in membranes, this article will review the work that has been done in the two major classes of hydrogen separation membranes: hydrogen-selective membranes and hydrogen-rejective membranes. In hydrogen-selective membranes, the very small size of the hydrogen molecule is exploited to allow rapid diffusion of hydrogen through the membrane while excluding other gases. Hydrogen-rejective membranes use the significantly higher sorption of other gases to overcome the advantages of the small size of the hydrogen molecule. The discussion of these two types of membranes will be followed by a presentation of the current state of the art with regard to polymeric membranes for hydrogen separation and a discussion of the predictions for future applications and advancements in this area.
Polymeric Facilitated Transport Membranes for Hydrogen Purification
Authors: Hägg May-Britt , Quinn Robert
Published: February 2011

The most widely used method of hydrogen production, steam methane reforming, yields a product stream consisting mainly of hydrogen (H2) and carbon dioxide (CO2). Purification of this product is currently accomplished using amine-based acid gas scrubbers or pressure swing adsorption technology. Membranes are well suited to bulk CO2 removal and offer a viable alternative to these established technologies. This review considers one type of such membranes, polymeric facilitated transport membranes. These membranes selectively permeate CO2 by means of a reversible reaction between the gas and the membrane material. In addition, the membrane provides a barrier to H2 permeation. The result is removal of the CO2 contaminant and recovery of the H2 product at high pressure, eliminating the need for recompression prior to use or storage. A wide range of polymeric materials have been investigated, including ion-exchange resins, hydrophilic polymers blended with CO2-reactive salts, polyelectrolytes, fixed-site carrier polymers, and biomimetic materials. This review provides a description of the reaction chemistry of facilitated transport, a summary of membrane permselective properties, and suggestions for future research efforts.
Microporous Silica and Zeolite Membranes for Hydrogen Purification
Authors: Verweij Henk , Lin Y.S. , Dong Junhang
Published: February 2011

Microporous amorphous silica and zeolite membranes are made as thin films on a multilayer porous support. The membranes have a network of connected micropores with ∼0.5–nm diameters. Net transport of small molecules on this network occurs under the driving force of a gradient in chemical potential. Favorable combinations of sorption selectivity and diffusion mobility in the membrane materials lead to high H2fluxes and good selectivity with respect to other gases. The membranes show potential for application in H2separation under harsh conditions. Amorphous silica membranes show very high H2fluxes because they can be made very thin; silicalite-type zeolite membranes are expected to have a better operational stability. To make the membranes a viable option, improvements are needed in reducing membrane defects and manufacturing costs and enhancing reproducibility and operational stability. This article summarizes the state of the art, provides relevant definitions, and outlines the base design and long-term specifications of viable supported membrane structures. This is followed by an overview of transport properties, synthesis, and operational stability of the membrane and the supporting structures. Directions for future research programs are provided by demonstrating how the selection of the actual membrane composition and supporting structure can be derived from an application-based design. The success of such a design depends critically on fundamental studies of membrane transport, strength, and operational stability.
The Intersection of Biology and Materials Science
Authors: Whitesides George M. , Wong Amy P.
Published: February 2011

This article is based on the plenary address given by George M. Whitesides of Harvard University on March 30, 2005, at the Materials Research Society Spring Meeting in San Francisco. Materials science and biomedicine are arguably two of the most exciting fields in science today. Research at the border between them will inevitably be a major focus, and the applications of materials science to problems in biomedicine—that is, biomaterials science—will bud into an important new branch of materials science. Accelerating the growth of this area requires an understanding of two very different fields, and being both thoughtful and entrepreneurial in considering “Why?” “How?” and “Where?” to put them together. In this fusion, biomedicine will, we believe, set the agenda; materials science will follow, and materials scientists must learn biology to be effective.
Pharmaceutical Cocrystals: An Emerging Approach to Physical Property Enhancement
Authors: Jones William , Motherwell W.D. Samuel , Trask Andrew V.
Published: February 2011

Pharmaceutical cocrystals are crystalline molecular complexes containing therapeutic molecules. They represent an emerging class of pharmaceutical materials offering the prospect of optimized physical properties. This article highlights important opportunities and challenges associated with the design and synthesis of pharmaceutical cocrystals. Cocrystallization is first placed into context with the more established approaches to physical property optimization of polymorph, hydrate, and salt selection. A directed, intermolecular-interaction-based approach to cocrystal design is described. The enhancement of specific physical properties, such as dissolution rate and physical stability, is illustrated by summarizing several recent reports. Synthetic approaches to cocrystallization are considered; in particular, the selectivity and screening-related opportunities afforded by solid-state grinding and solvent-drop grinding methods are discussed. Finally, an outlook on future developments summarizes the growth potential in this field, especially with regard to targeted, informatics-driven cocrystal screening approaches.
Intelligent Biomaterials as Pharmaceutical Carriers in Microfabricated and Nanoscale Devices
Authors: Peppas Nicholas A.
Published: February 2011

The emergence of micro- and nanoscale science and engineering has provided new avenues for engineering materials with macromolecular and even molecular-scale precision, leading to diagnostic and therapeutic technologies that will revolutionize the way healthcare is administered. Biomaterials have evolved from off-the-shelf products to materials designed with molecular precision to exhibit the desired properties for a specific application, often mimicking biological systems. Controlling interactions at the level of natural building blocks, from proteins to cells, facilitates the novel exploration, manipulation, and application of living systems and biological phenomena. In addition, polymer networks with precisely engineered binding sites have been created via molecular imprinting, where functional monomers are preassembled with a target molecule and then the structure is locked with network formation. Nanoscale science and engineering have accelerated the development of novel drug delivery systems and led to enhanced control over how a given pharmaceutical is administered, helping biological potential to be transformed into medical reality. Micro- and nanoscale devices have been fabricated using integrated-circuit processing techniques, enabling strict temporal control over drug release. The advantages of these microdevices include simple release mechanisms, very accurate dosing, the capability of complex release patterns, the potential for local delivery, and possible biological drug stability enhancement by means of storage in a microvolume that can be precisely controlled. In particular, the development of polymer systems that are able to interact with their environment in a thermodynamically responsive manner has led to novel intelligent biomaterials and applications. Intelligent biomedical materials can be used for the delivery of drugs, peptides, and proteins; as targeting agents for site-specific delivery; or as components for the preparation of protein or drug conjugates. These intelligent materials are attractive options as functional components in micro- and nanodevices because of the ease with which recognition and actuation properties can be precisely tailored. Recent developments in intelligent materials and nano- or microdevices for drug delivery systems are the emphasis of this review, which addresses the use of intelligent biomedical materials as carriers for the development of novel pharmaceutical formulations.
Use of Nanotechnologies for Drug Delivery
Authors: Shah Parag
Published: February 2011

The emerging field of nanotechnology has an enormous potential contribution to make to the field of pharmaceutical materials science. The advantages of drug nanoparticles can be as simple as dissolution rate enhancement through increased surface area or as complex as targeted delivery through novel pathways. However, the application of many nanoscale technologies has been slow because of difficulties controlling the drug form with decreasing particle size and maintaining chemical and physical stability upon storage. Advancing beyond these limitations requires a unique understanding of both the material properties of the active ingredients as well as the physical chemistry of the nano-sized particle. This article will examine the current challenges facing the pharmaceutical industry in applying nanotechnology, with a focus on the deficiencies in understanding that need to be addressed to move forward.
Materials Informatics
Authors: Rodgers John R. , Cebon David
Published: February 2011

Global markets are pressuring the materials industries to reduce the time span between materials research and materials development. In particular, current approaches to the development and insertion (deployment) of advanced materials in military systems are too time-intensive and expensive. Despite the large investments in defense systems, insertion is not certain, since materials development is often not linked to the system designer needs, with the results frequently being that the materials do not meet their requirements. There is potentially a high payoff for developing methodologies that will accelerate the insertion of materials, thereby saving millions of investment dollars. All industries engaged in developing advanced materials are searching for new methodologies to solve these problems.

Once a new material has been developed, it must be characterized and modeled. Otherwise, components using it cannot be analyzed, and consequently, it cannot be used in engineering products. Therefore, exploiting the full benefits of new (and existing) engineering materials requires specialized informatics tools for data capture, management, analysis, and dissemination. Advances in computing power, coupled with computational modeling and simulation and materials properties databases, will enable materials scientists and engineers to meet these challenges.

The articles in this issue of MRS Bulletin show a variety of applications of the methodologies that are employed in using materials informatics approaches to materials and engineering product development.
Data Mining in and around Crystal Structure Databases
Authors: Page Yvon Le
Published: February 2011

Data mining of crystal structure databases is performed with methods using deduction, semiempirical heuristic principles, or artificial intelligence to create new information from crystal structure data. In this article, enlightening examples, ranging from a systematic search for new ferroelectric materials to ultrahard, ductile, or high-dielectric-permittivity materials, are detailed, with numerous references providing a handle on the state of the art. This activity is just leaving infancy, especially for its ab initio aspects, with the brightest future ahead. Data mining will clearly guide expensive experiments through inexpensive computations for decades to come. This perspective greatly enhances the value of structure data patiently archived within crystal structure databases for nearly a century now.
Digital Materials Design: Computational Methodologies as a Discovery Tool
Authors: Wu Ping
Published: February 2011

To cope with the dynamic social and market demands for advanced materials, new research strategies have to be developed that go beyond the commonly accepted trial-and-error approaches. To this end, a computational materials design platform, digital materials design (DMD), has been created based on well-established fundamental laws, powerful computing, and computational technology. DMD based on computer simulation may produce data that identify overlooked materials behaviors, which then may lead to new theory to explain them, and further to the design of real experiments to fabricate and test the materials. In this review, an illustration of computational methods used in DMD will be given, followed by applications based on two case studies: (1) the design of chemical additives, and (2) the realization ofp-type ZnO. Similarly, many effective and efficient materials designs have been performed in the using DMD for various industrial applications, which further demonstrate that DMD, and computational modeling in general, is an invaluable tool for materials discovery.
Combinatorial Experimentation and Materials Informatics
Authors: Takeuchi Ichiro , Lippmaa Mikk , Matsumoto Yuji
Published: February 2011

High-throughput experimentation is effective in systematically producing large and diverse data sets. The marriage of combinatorial materials science and informatics is a natural one, and results are beginning to emerge from the integration of elements of materials informatics with data from combinatorial libraries. We discuss data management issues in high-throughput experimentation and highlight recent examples where data-mining tools are being implemented for extracting knowledge and predicting new compounds, with an emphasis on electronic materials.
Atomic Control of the Electronic Structure at Complex Oxide Heterointerfaces
Authors: Hwang Harold Y.
Published: February 2011

The following article is based on the Outstanding Young Investigator Award presentation given by Harold Y. Hwang of the University of Tokyo on March 29, 2005, at the Materials Research Society Spring Meeting in San Francisco. Hwang was cited for “innovative work on the physics of transition-metal oxides and the atomic-scale synthesis of complex oxide heterostructures.” Perovskite oxides range from insulators to superconductors and can incorporate magnetism as well as couple to phonon instabilities. The close lattice match between many perovskites raises the possibility of growing epitaxial thin-film heterostructures with different ground states that may compete or interact. The recent development of superconducting Josephson junctions, magnetic tunnel junctions, ferroelectric memory cells, and resistive switching can be considered examples within this new heteroepitaxial family. In this context, Hwang presents his studies of electronic structure at atomically abrupt interfaces grown by pulsed laser deposition. Some issues are generic to all heterointerfaces, such as the stability of dopant profiles and diffusion, interface states and depletion, and interface charge arising from polarity discontinuities. A more unusual issue is the charge structure associated with Mott insulator/band insulator interfaces. The question is, how should one consider the correlated equivalent of band bending? This semiconductor concept is based on the validity of rigid single-particle band diagrams, which are known to be an inadequate description for strongly correlated electrons. In addition to presenting an interesting scientific challenge, this question underlies the attempts to develop new applications of doped Mott insulators in device geometries.
Thermoelectric Materials, Phenomena, and Applications: A Bird's Eye View
Authors: Tritt Terry M. , Subramanian M. A.
Published: February 2011

High-efficiency thermoelectric (TE) materials are important for power-generation devices that are designed to convert waste heat into electrical energy.They can also be used in solid-state refrigeration devices.The conversion of waste heat into electrical energy may play an important role in our current challenge to develop alternative energy technologies to reduce our dependence on fossil fuels and reduce greenhouse gas emissions.

An overview of various TE phenomena and materials is provided in this issue ofMRS Bulletin. Several of the current applications and key parameters are defined and discussed.Novel applications of TE materials include biothermal batteries to power heart pacemakers, enhanced performance of optoelectronics coupled with solid-state TE cooling, and power generation for deep-space probes via radioisotope TE generators.A number of different systems of potential TE materials are currently under investigation by various research groups around the world, and many of these materials are reviewed in the articles in this issue.These range from thin-film superlattice materials to large single-crystal or polycrystalline bulk materials, and from semiconductors and semimetals to ceramic oxides.The phonon-glass/electron-crystal approach to new TE materials is presented, along with the role of solid-state crystal chemistry.Research criteria for developing new materials are highlighted.
Complex Oxide Materials for Potential Thermoelectric Applications
Authors: Koumoto Kunihito , Terasaki Ichiro , Funahashi Ryoji
Published: February 2011

Layered CoO2 materials are excellent candidates for potential thermoelectric applications. Their single crystals show good p-type thermoelectric properties at temperatures higher than 800K in air.Recently, the mechanism of thermoelectric properties was clarified through a discussion of electronic and crystallographic structure. In order to fabricate thermoelectric modules possessing good power-generation properties, thermoelectric materials and metallic electrodes must be connected with low contact resistance and high mechanical strength.It has been found that good junctions can be formed using Ag paste including p- and n-type oxide powders.The role of spin entropy contributions to thermopower will be presented, in connection with strong electron correlation and triangular lattices.
Properties of Nanostructured One-Dimensional and Composite Thermoelectric Materials
Authors: Rao Apparao M. , Ji Xiaohua , Tritt Terry M.
Published: February 2011

Over a decade ago, Dresselhaus predicted that low-dimensional systems would one day serve as a route to enhanced thermoelectric performance.In this article, recent results in the thermoelectric properties of nanowires and nanotubes are discussed. Various synthesis techniques will be presented, including chemical vapor deposition for the growth of thermoelectric nanostructures in templated alumina.Electrical transport measurements of carbon nanostructures, such as resistivity and thermopower, have revealed some very interesting thermoelectric properties.Challenges still remain concerning the measurement of individual nanostructures such as nanowires.Much work has been performed on the thermoelectric properties of carbon nanotubes, and these results will be highlighted.In addition, routes for enhanced thermoelectric materials have focused on incorporating nanostructures within the bulk materials.The role of these “hybrid composite structures” based on nanomaterials incorporated into the bulk matrix and the potential for enhanced performance are discussed.
Materials for Optical Data Storage
Authors: Coufal Hans , Dhar Lisa
Published: February 2011

The development of recording materials has been a critical component in the advancement of optical data storage. The continual need for improved performance in both consumer and business applications has pushed forward the capabilities of optical storage. In this issue of MRS Bulletin, we review some of the important developments in the materials behind established technologies such as compact discs, digital versatile discs, and magneto-optical recording; the emerging technology of blue recording; and two technologies that seek to extend the performance roadmap for optical storage, multilayer and holographic recording.
Materials for Optical Disc Substrates
Authors: Bruder Friedrich-Karl , Douzinas Konstantinos , Franz Uli , Haese Wilfried , Oser Rafael
Published: February 2011

Optical data storage has become the mainstream technology during the past two decades for distributing audio, video, and software content as well as for recording and archiving personal data. The continuous demand for ever-higher storage capacities and faster data transfer has led to the development of three disc format families using infrared (compact discs), red (digital versatile discs), and blue lasers (Blu-ray discs or high-density DVDs). Substrate materials used in optical discs need to possess a complex property profile with sufficient optical, rheological, mechanical, and processing characteristics to ensure cost-efficient replication, good read/write performance, and long-term media stability. Bisphenol-A polycarbonate (BPA-PC) is the substrate material of choice and has undergone several optimization cycles to always meet new format specifications.
High-Performance Polymer Recording Materials for Holographic Data Storage
Authors: Dhar Lisa
Published: February 2011

Holographic storage is considered a promising successor to currently available optical storage technologies. Enabling significant gains in both data transfer rates and storage densities, holographic storage and its capabilities have gained a great deal of recent attention.One of the primary challenges in the advancement of holographic storage has been the development of suitable recording materials.In this article, we provide a brief introduction to holographic storage and its potential advantages over current technologies, outline the requirements for recording materials, and survey candidate materials.We end by highlighting recent progress in photopolymer materials that has produced materials that satisfy the requirements for holographic storage and have enabled significant demonstrations of the viability of this technology.
Captured Molecules in Coordination Frameworks
Authors: Tanaka Daisuke , Kitagawa Susumu
Published: February 2011

In recent years, a new class of porous materials based on a combination of organic components and metal centers has emerged, namely, microporous coordination polymers (MCPs), in which the chemical properties as well as the pore dimensions affect the incorporation of “guest” molecules within the pores. In this article, we describe the ability of MCPs to store gas molecules, which is ascribed to framework regularity and high porosity, and the unique capacity of certain MCPs to capture molecules selectively by well-defined interactions with organic functional groups.
Magnetically Ordered Molecule-Based Materials
Authors: Miller Joel S.
Published: February 2011

Magnetic ordering that typically occurs for extended three-dimensional structured inorganic materials has also been established for several organic- and molecule-based materials. In addition to the characterization of new magnetic materials, new phenomena and combinations of phenomena have been observed for molecule-based materials. An overview of the new materials and phenomena is presented.
Assembling Photo- and Electroresponsive Molecules and Nano-Objects
Authors: Busby Michael , De Cola Luisa , Kottas Gregg S. , Popović Zoran
Published: February 2011

The self-assembly of small molecules into large, functional nanostructures has led to the construction of supramolecular systems, both in solution and on solid substrates, with defined dimensions that display unique properties through collective interactions, much like natural systems. In this article, we show how one assembles photo- and electroluminescent molecules through coordination chemistry for the purpose of producing novel materials that can be used for displays and lighting applications. In a stepwise process, we discuss the design and synthesis of the components, their spectroscopic behavior, and finally the properties arising from the assembly. We then move from molecules to more complex systems such as zeolite L nano-objects that can be used as nanocontainers and functionalized in different ways. We show how it is possible to organize rods of micron length in a geometrically controlled manner in solution and on surfaces. The assemblies are built by coordinative bonds and are luminescent materials that can be constructed from fluorescent building blocks, with potential applications as optoelectronic materials, in analogy to their molecular counterparts.
Laser Direct-Write Techniques for Printing of Complex Materials
Authors: Arnold Craig B. , Serra Pere , Piqué Alberto
Published: February 2011

This article reviews recent developments in laser direct-write addition (LDW+) processes for printing complex materials. Various applications, ranging from small-scale energy storage and generation devices to tissue engineering, require the ability to deposit precise patterns of multicomponent and multiphase materials without degrading desirable properties such as porosity, homogeneity, or biological activity. Structurally complex inorganic materials for the successful fabrication of alkaline and lithium-based microbatteries, micro-ultracapacitors, and dye-sensitized micro solar cells are shown on various low-processing-temperature and flexible substrates using LDW+. In particular, the ability to deposit thick layers while maintaining pattern integrity allows devices produced in this manner to exhibit higher energy densities per unit area than can be achieved by traditional thin-film techniques. We then focus on more complex systems of living and biologically active materials. Patterns of biomaterials such as proteins, DNA, and even living cells can be printed using LDW+ with high spatial and volumetric resolution on the order of a picoliter or less, without compromising the viability of these delicate structures. These results provide for highly selective sensor arrays or cell seeding for tissue engineering. Finally, we review recent work on LDW+ of entire semiconductor circuits, showing the broad range of applications this technique enables.
Direct-Writing of Three-Dimensional Structures Using Laser-Based Processes
Authors: Stuke M. , Mueller K. , Mueller T. , Williams K. , Oliver R. , Ohlberg D.A.A. , Fuhr G. , Williams R. S.
Published: February 2011

Three-dimensional structures of selected materials can be written directly to the precise locations required using laser exposure of suitable gaseous precursor mixtures. Writing speeds exceeding 50 μm/s can be achieved. Examples presented in this work include the creation of a tiny time-of-flight laser ionization mass spectrometer, laserdriven movable micro-objects, and an ac electric-field microcage for storage, handling, and transferring small neutral objects in aqueous solution. The impact for lasercontrolled site-selective growth of carbon nanotube cables is demonstrated.
Dripping, Jetting, Drops, and Wetting: The Magic of Microfluidics
Authors: Utada A. S. , Chu L.-Y. , Fernandez-Nieves A. , Link D. R. , Holtze C. , Weitz D. A.
Published: February 2011

The following article is based on the Symposium X presentation given by David A. Weitz (Harvard University) on April 11, 2007, at the Materials Research Society Spring Meeting in San Francisco. The article describes how simple microfluidic devices can be used to control fluid flow and produce a variety of new materials. Based on the concepts of coaxial flow and hydrodynamically focused flow, used alone or in various combinations, the devices can produce precisely controlled double emulsions (droplets within droplets) and even triple emulsions (double emulsions suspended in a third droplet). These structures, which can be created in a single microfluidic device, have various applications such as encapsulants for drugs, cosmetics, or food additives.
Advances in the Materials Science of Skin: A Composite Structure with Multiple Functions
Authors: Subramanyan K. , Misra M. , Mukherjee S. , Ananthapadmanabhan K. P.
Published: February 2011

This article gives the foundation for understanding the structure and function of human skin and its layers. Skin is our first line of defense against the penetration of external chemicals and bacteria into the body and of water loss from the body. Skin's visual and tactile properties are very much linked to appearance and beauty. Skin treatments as simple as washing with soap affect the mechanics of skin properties, making it dry and brittle versus smooth and elastic. Likewise, natural aging, hormonal changes, and sun exposure affect the properties of skin. Mild cleansing, moisturizer treatments, and regular use of sunscreens can, however, help skin maintain and even improve its quality, appearance, and functional properties.
Silicone Polymers in Skin Care
Authors: O'Lenick Anthony J. , O'Lenick Kevin A.
Published: February 2011

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.
Systematic Coarse Graining: “Four Lessons and A Caveat” from Nonequilibrium Statistical Mechanics
Authors: Öttinger Hans Christian
Published: February 2011

With the guidance offered by nonequilibrium statistical thermodynamics, simulation techniques are elevated from brute-force computer experiments to systematic tools for extracting complete, redundancy-free, and consistent coarse-grained information for dynamic systems. We sketch the role and potential of Monte Carlo, molecular dynamics, and Brownian dynamics simulations in the thermodynamic approach to coarse graining. A melt of entangled linear polyethylene molecules serves us as an illustrative example.