Despite modern advancements in sterilization and aseptic procedures, bacterial infections remain a major and significant impediment to the long-term success of medical implants and devices, including catheters, artificial prosthetics, and subcutaneous sensors. It has been estimated that upward of 60% of nosocomial, or hospital-acquired, infections are associated with implants, with an estimated one million cases per year in the United States alone. Current treatment regimens primarily rely on the systemic administration of antibiotics or local administration through irrigation of the surgical site. However, after decades of prophylactic antibiotic use, high infection rates continue to persist, particularly with the emergence of drug-resistant strains such as methicillin-resistant Staphylococcus aureus (MRSA). Consequently, recent research efforts have focused on the use of non-antibiotic-based coatings to inhibit bacteria colonization and subsequent biofilm formation on implant surfaces. In particular, advancements in surface treatment strategies and ongoing development of new antimicrobial agents have led to encouraging progress in the design of better coatings. Here, we present and discuss representative examples of novel surface engineering approaches to address device-associated infections, focusing in particular on coatings that can be easily administered onto implant material surfaces.

In recent years, bio-based products have been of great interest since sustainable development policies have tended to expand with decreasing reserves of fossil fuels and growing concerns for the environment. Consequently, biodegradable and renewable polymers have been the topic of significant research. These polymers can mainly be classified as agro-polymers (starch, chitosan) and biopolyesters (polyhydroxyalkanoates, poly(lactic acid)). Unfortunately, for certain applications, these bio-based polymers cannot be fully competitive with conventional thermoplastics since some of their properties are too weak. Therefore, to extend the range of their applications, current bio-based polymers have to be reformulated. Some of the most promising are nano-biocomposites, where nano-sized fillers are dispersed into a biopolymer matrix, which could yield a range of improved properties (stiffness, permeability). This article reports the most recent developments in renewable nano-biocomposites based on the use of nanoclay fillers.

Energy storage is a critical hurdle to the success of many clean energy technologies. Batteries with high energy density, good safety, and low cost can enable more efficient vehicles with electrified drive trains, such as hybrid electric vehicles, electric vehicles, and plug-in hybrid electric vehicles. They can also provide energy storage for intermittent energy sources, such as wind and solar. Today, and for the foreseeable future, rechargeable lithium batteries deliver the highest energy per unit weight or volume at reasonable cost. Many of the important properties of battery materials can be calculated with first-principles methods, making lithium batteries fertile ground for computational materials design. In this article, we review the successes and opportunities in using first-principles computations in the battery field. We also highlight some technical challenges facing the accurate modeling of battery materials.

Electric power grid applications impose many requirements on high-temperature superconductor (HTS) materials. In addition to a high superconductor transition temperature, these include all the parameters enabling a cost-effective, robust, and high-performance wire: high current-carrying capability in relevant ranges of field and temperature, flexibility and mechanical strength in a wire form, electrical and chemical stability, low ac loss, high wire uniformity, and low wire manufacturing cost with high reproducibility and yield. This daunting list explains why it has taken so long to bring HTS wires to where they are today—starting to be used in commercial power projects. The benefits of these wires are very significant: high efficiency and power density in an accessible temperature range, enabling high-capacity and easily installed cables, compact and powerful rotating machinery, and unique current-limiting functionality. However, the job is not done. Improved wire properties and reduced manufacturing costs of existing materials will further broaden the impact of this technology. Meanwhile the search for new materials—and for room-temperature superconductors—must continue, with more attention to thermal fluctuations, flux creep, and reduced anisotropy, which are critical to their application potential.

We describe two ways in which pulsed lasers can be used to increase efficiency in photovoltaic devices. First, pulsed-laser hyperdoping can introduce dopants into a semiconductor at non-equilibrium concentrations, which creates an intermediate band in the bandgap of the material and modifies the absorption coefficient. Second, pulsed-laser irradiation can enhance geometric light trapping by increasing surface roughness. Hyperdoping in silicon enables absorption of photons to wavelengths of at least 2.5 μm, while texturing enhances the absorptance to near unity at all absorbing wavelengths. This article reviews both effects and comments on outstanding questions and challenges in applying each to increasing the efficiency of photovoltaic devices.

Research on contact materials in silicon semiconductor devices has recently gained significant momentum due to the increasing performance demands as the complementary metal oxide semiconductor technology advances. Applications include transistor materials such as gate electrodes and contacts to highly doped semiconductors substrates. This review will discuss the key issues in the development of metal gate electrodes with high-κ dielectrics to replace the conventional polycrystalline silicon electrode. Challenges in establishing a work function measurement technique, the role of the metal/high-κ interface in modulating the effective work function, and a review of leading industry solutions will be discussed.

Carbon nanotubes (CNTs) are high aspect ratio conducting nanocylinders possessing unprecedented mechanical, thermal, optical, and electronic properties. They are ideal building blocks for use in assembling a randomly oriented, highly connected nanoporous network. When this network is deposited on top of a substrate surface as a thin film with a thickness in the range of 10–100 nm, it becomes a transparent conducting film—an ubiquitous material, currently dominated by tin-doped indium oxide (ITO). This article reviews recent progress in CNT transparent conducting films and discusses fundamental properties of CNTs important for the formation of these films, methods for CNT dispersion and assembling CNTs into transparent conducting films, properties of the CNT transparent conducting films, and issues remaining to be solved in order to make these films a commercially viable alternative to ITO.

Since the emergence of tissue engineering (TE), numerous researchers, particularly in the areas of materials, biological science, and engineering, have aimed to provide viable substitutes for the repair and regeneration of musculoskeletal and organ tissues. Bone TE has been extensively explored to mimic the anatomical geometry of bone with varied pore size distribution and varying mechanical properties in a radial direction (a functional gradient). This TE approach was explored to promote faster functional recovery of defective bones due to congenital, traumatic, or degenerative reasons. The present study integrated an appropriate additive manufacturing or rapid prototyping technique with automated computer-aided design models. This process was applied to the manufacture of a functionally graded scaffold (FGS). The FGS system takes into consideration both microscale anatomical geometries and mechanical properties of the native bone via an established porosity-stiffness relationship. Experimental verification of the FGS model was carried out by the fabrication of a femur bone segment using a selective laser sintering system. The physical femur model demonstrated good replication of the FGS structure that was generated. Future work aims to implement the FGS system for other musculoskeletal and organ tissues and integrate the current work with the authors’ in-house developed “computer aided system for tissue scaffolds” or CASTS system.

As the complexity of global materials science challenges increases, so does the need for materials science and engineering literacy and career recruitment. Many funding agencies are addressing this by including requirements for achieving broader impacts (e.g., National Science Foundation grants, European Commission Framework), and resources have been created from a variety of sources to help. This article addresses the issue of how to translate materials science concepts into K–12 outreach activities, with an emphasis on how to use the human, physical, and information resources available. Researchers may best reach their outreach objectives by distilling content rather than diluting it, connecting on a human level, highlighting the true nature of science, not reinventing the wheel, being a role model, and having fun. Initiatives that support outreach efforts are referenced and include examples from the Materials Research Society.

The history of superconductivity in MgB2 has been short, but intense. Ten years after its discovery, the two-gap mechanism of superconductivity in MgB2 has been mastered to a considerable extent while developing its superconducting properties in wires that meet the technical and economic requirements of industrial applications. The hope for dry superconductivity (i.e., without any liquid cryogen) using this simple and low-cost material has been recently fulfilled, with current commercial availability of MgB2-based dry MRI machines. We expect that scientific progress in understanding and developing MgB2 conductors will continue, strengthening the base for further deployment of MgB2 in applications. This article presents the main scientific and technical highlights of MgB2, describing its two-gap superconductivity, progress in improving its superconducting properties, the advances toward making MgB2 a fully recognized practical superconductor, and its prospects for ongoing and upcoming applications.

Rapid prototyping (RP) technologies, which are based on computer-aided design and computer-aided manufacturing, are widely employed in traditional industries. They are capable of achieving extensive and detailed control over the architecture of objects to be formed and therefore are increasingly used in the biomedical engineering field. Selective laser sintering (SLS), a versatile RP technique, uses a laser beam to selectively sinter powdered materials to form three-dimensional objects according to designs that can be based on data obtained from computer-based medical imaging technologies. In this article relating to biomedical applications, the principle, materials, machine modification, and parameter optimization for SLS are reviewed. Biomedical applications of SLS, especially in the fabrication of tissue engineering scaffolds and drug/biomolecule delivery vehicles, are presented and discussed. SLS exhibits great potential for many applications in biomedical engineering.

The impact of contact materials on the performance of nanostructured devices is expected to be significant. This is especially true since size scaling can increase the contact resistance and induce many unseen phenomenon and reactions that greatly impact device performance. Nanowire and nanoelectromechanical switches are two emerging nanoelectronic devices. Nanowires provide a unique opportunity to control the property of a material at an ultra-scaled dimension, whereas a nanoelectromechanical switch presents zero power consumption in its off state, as it is physically detached from the sensor anode. In this article, we specifically discuss contact material issues related to nanowire devices and nanoelectromechanical switches.

Networks of nanoscale conductors such as carbon nanotubes, graphene, and metallic nanowires are promising candidates to replace metal oxides as transparent conductors. However, very few previous reports have described nanostructured thin films that reach the standards required by industry for high-performance transparent electrodes. In this review, we analyze the sheet resistance and transmittance data extracted from published literature for solution processed, nanostructured networks. In the majority of cases, as their thickness is reduced below a critical value, nanoconductor networks undergo a transition from bulk-like to percolative behavior. Such percolative behavior is characteristic of sparse networks with limited connectivity and few continuous conductive paths. This transition tends to occur for films with a transmittance between 50% and 90%, which means that the properties of highly transparent films are predominately limited by percolation. Consequently, to achieve low resistance coupled with high transparency, the networks must be much more conductive than would otherwise be the case. We show that highly conductive networks of metallic nanowires appear to be the most promising candidate to replace traditional transparent electrode materials from a technical standpoint. However, many other factors, including cost, manufacturability, and stability, will have to be addressed before commercialization of these materials.

Atomic layer deposition (ALD) uses self-limiting chemical reactions between gaseous precursors and a solid surface to deposit materials in a layer-by-layer fashion. This process results in a unique combination of attributes, including sub-nm precision, the capability to engineer surfaces and interfaces, and unparalleled conformality over high-aspect ratio and nanoporous structures. Given these capabilities, ALD could play a central role in achieving the technological advances necessary to redirect our economy from fossil-based energy to clean, renewable energy. This article will survey some of the recent work applying ALD to clean energy conversion, utilization, and storage, including research in solid oxide fuel cells, thin-film photovoltaics, lithium-ion batteries, and heterogenous catalysts. Throughout the manuscript, we will emphasize how the unique qualities of ALD can enhance device performance and enable radical new designs.

There are a large number of natural fibers that have the potential to replace synthetic fibers made from glass, carbon, and polymers as the reinforcing phase in composites. Interest in these fibers has increased, as they offer a sustainable, readily available, high specific modulus option. The high modulus of cellulose crystals makes them attractive as a reinforcing phase in composites. These cellulose crystals are the key structural component in natural fibers, but the complex microstructure of the fiber means that the full value of the cellulose crystal modulus cannot be utilized. Moreover, the surface of natural fibers can have varying chemistry depending on the pretreatment of the fiber and the degree to which lignin and other hydrophobic materials are removed from the fiber. In addition, cellulose swells in contact with water, and this can degrade the properties of the fiber and composite. A better understanding of the surface properties and techniques to control the composite interface are required if natural fibers are to fulfill their potential.

The drive to make solar energy competitive with conventional energy sources has prompted the investigation of new photoconversion technologies, often referred to as third-generation photovoltaics, which have both lower cost and improved efficiency compared to existing technologies. In that framework, nanostructured materials, such as nanocrystals, nanowires, and nanotubes, occupy a prominent place because of their potential advantages over crystalline or thin-film photovoltaics technologies—high tunability of the bandgap via size control, strong band-edge absorption coefficient, efficient multiple-exciton generation by a single photon, and possibly high up-conversion efficiency. The ability to control the size, shape, composition, and surface termination of nanostructures provides new degrees of freedom that are inaccessible in conventional solar cell architectures. At the same time, the ability to explore this vast configuration space by synthesis and characterization alone is limited, which makes computational interrogation of the electronic and optical properties of nanostructures particularly valuable. In recent years, the convergence of new algorithms and new computational capabilities has made it possible for the first time to perform accurate electronic-structure calculations for large nanostructures. This article reviews recent developments in both semi-empirical and first-principles atomistic electronic structure methods that have led to accurate predictions and to a better understanding of carrier generation, relaxation, and recombination processes in nanostructured materials.

This review focuses on recent developments in the study of hydrogen generation from water splitting using photoelectrochemical (PEC) cells based on metal oxide (MO) nanomaterials. The emphasis is on the unique properties of MO nanostructures and their advantages as well as limitations for PEC solar hydrogen generation. While abundant and stable, metal oxide nanomaterials tend to have weak visible light absorption that limits their use for solar energy conversion. In addition, MO nanomaterials tend to exhibit a high density of trap states or defect sites that limit their overall efficiency. Different strategies have been developed to enhance visible light absorption (e.g., doping, dye, or quantum dot sensitization and band structure engineering using composite structures) as well as to enhance transport by reducing the density of trap states via surface modification, improving crystallinity, or using 1D structures. In some cases, combining different strategies has led to strong synergistic effects. Recent studies point to the importance and promise of engineering electronic band structure for improving PEC performance of MO nanostructures for hydrogen generation and other potential applications.

Ongoing technological advances in such disparate areas as consumer electronics, transportation, and energy generation and distribution are often hindered by the capabilities of current energy storage/conversion systems, thereby driving the search for high-performance power sources that are also economically viable, safe to operate, and have limited environmental impact. Electrochemical capacitors (ECs) are a class of energy-storage devices that fill the gap between the high specific energy of batteries and the high specific power of conventional electrostatic capacitors. The most widely available commercial EC, based on a symmetric configuration of two high-surface-area carbon electrodes and a nonaqueous electrolyte, delivers specific energies of up to ∼6 Whkg–1 with sub-second response times. Specific energy can be enhanced by moving to asymmetric configurations and selecting electrode materials (e.g., transition metal oxides) that store charge via rapid and reversible faradaic reactions. Asymmetric EC designs also circumvent the main limitation of aqueous electrolytes by extending their operating voltage window beyond the thermodynamic 1.2 V limit to operating voltages approaching ∼2 V, resulting in high-performance ECs that will satisfy the challenging power and energy demands of emerging technologies and in a more economically and environmentally friendly form than conventional symmetric ECs and batteries.

Many bacteria grow attached to a surface as biofilms. Several factors dictate biofilm formation, including responses by the colonizing bacteria to their environment. Here we review how bacteria use cell-cell signaling (also called quorum sensing) and motility during biofilm formation. Specifically, we describe quorum sensing and surface motility exhibited by the bacterium Pseudomonas aeruginosa, a ubiquitous environmental organism that acts as an opportunistic human pathogen in immunocompromised individuals. P. aeruginosa uses acyl-homoserine lactone signals during quorum sensing to synchronize gene expression important to the production of polysaccharides, rhamnolipid, and other virulence factors. Surface motility affects the assembly and architecture of biofilms, and some aspects of motility are also influenced by quorum sensing. While some genes and their function are specific to P. aeruginosa, many aspects of biofilm development can be used as a model system to understand how bacteria differentially colonize surfaces.

Well-ordered arrays of one-dimensional semiconductors, such as titania nanotubes (NTs), have attracted attention as a promising new film architecture for dye- and semiconductor-sensitized solar cells. The film architecture in sensitized solar cells combines light absorption, charge injection, and charge-carrier transport to generate electrical power and is, therefore, a key component in determining the photoconversion efficiency of a cell. Because of the arrays’ distinct combination of physical, electrical, and optical properties, the conversion efficiencies of TiO2 NT-based devices are rapidly catching up with those of the traditional nanoparticle-based cells. In this article, we briefly review the fabrication and morphology of the NT arrays and discuss the strong influence that the film architecture and individual NT structure exert on the light-harvesting and charge-collection properties of sensitized solar cells. Besides affecting the solar conversion efficiency, the morphological and electrical properties of the arrays also impact the cell fabrication process.