A closed-loop approach is adopted to implement strain rate control during the bulge test. Due to the difficulty of measuring strains directly, the technique is based on the conversion of displacement measurements to the corresponding strains using the plane-strain formulation. The necessary temporal evolution of the midpoint displacement of a rectangular diaphragm is derived under the condition of constant strain rate and is imposed as a control criterion. The technique is demonstrated on 500-nm-thick Au diaphragms by applying strain rates ranging from 2 × 10−6 to 2 × 10−4 s–1. By measuring the corresponding yield strength values, a strain rate sensitivity of 0.11 is obtained, which is close to what was previously reported on similar specimens using the microbending test.

For many years, a fundamental problem in contact mechanics, both tribology and indentation problems, has been the inability to see what is taking place—the buried-interface problem. Over the past few years, there have been developments whereby it has become possible to perform contact mechanics experiments in situ within a transmission electron microscope. These new experiments have been enabled by both the miniaturization of sensors and actuators and improvements in their mechanical stability and force sensitivity. New information is now becoming available about the nanoscale processes of sliding, wear, and tribochemical reactions, as well as microstructural evolution during nanoindentation such as dislocation bursts and phase transformations. This article provides an overview of some of these developments, in terms of both the advances in technical instrumentation and some of the novel scientific insights.

An antigenic mimic of the Ebola glycoprotein was synthesized and tested for its ability to be recognized by an anti-Ebola glycoprotein antibody. Epitope-mapping procedures yielded a suitable epitope that, when presented on the surface of a nanoparticle, forms a structure that is recognized by an antibody specific for the native protein. This mimic-antibody interaction has been quantitated through ELISA and QCM-based methods and yielded an affinity (Kd = 12 × 10−6 M) within two orders of magnitude of the reported affinity of the native Ebola glycoprotein for the same antibody. These results suggest that the rational design approach described herein is a suitable method for the further development of protein-based antigenic mimics with potential applications in vaccine development and sensor technology.

Oligomerically modified reactive montmorillonite clay was used in the preparation of aramid-layered silicate nanocomposites. The dispersion behavior of organoclay was monitored in the aramid matrix synthesized from 4-aminophenylsulfone and isophthaloyl chloride in dimethylacetamide. These polyamide chains were end-capped with carbonyl chloride groups to interact chemically with oligomerically modified layered silicate. Thin composite films containing 2 to 20 wt% of organoclay were probed for x-ray diffraction (XRD), transmission electron microscopy (TEM), mechanical testing, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and water absorption measurements. XRD and TEM results described the distribution level of clay platelets and morphology of hybrid materials. Mechanical measurements revealed that modulus and strength improved up to 6 wt% clay loading, while toughness of nanocomposites increased with the addition of 2 wt% clay content in the matrix. The elongation showed a decreasing trend with increasing clay content in the hybrids. Thermal-decomposition temperatures of the nanocomposites were in the range 225 to 450 °C. The glass-transition temperature increased up to 12 wt% addition of organoclay in the matrix relative to pristine aramid depicting interfacial interactions among the phases. Water absorption of the nanocomposites reduced with augmenting organoclay loading, indicating decreased permeability.

Li2M(WO4)2 (M = Co and Ni) were synthesized by a conventional solid-state reaction method and characterized by powder x-ray diffraction, Brunauer-Emmet-Teller (BET) measurement, ultraviolet-visible (UV-vis) diffuse reflectance spectra, Raman spectroscopy, and photocatalytic evaluation measurements. Photocatalytic water splitting results showed that Li2M(WO4)2 (M = Co and Ni) exhibited abilities for H2 evolution with Pt cocatalyst from an aqueous methanol solution and for O2 evolution from an aqueous AgNO3 solution under UV light irradiation. Theoretical calculation, absorbance analysis, and photocatalytic H2 evolution experiment revealed that the position of W 5d level shifted to the negative side with respect to the reduced potential of H+/H2. The photocatalytic H2 evolution over Li2M(WO4)2 is discussed from the view of crystal and electronic structure point.

BioSiC is a biomimetic SiC-based ceramic material fabricated by Si melt infiltration of carbon preforms obtained from wood. The microstructure of bioSiC mimics that of the wood precursor, which can be chosen for tailored properties. When the remaining, unreacted Si is removed, a SiC material with interconnected porosity is obtained. This porous bioSiC is under study for its use as a medical implant material. We have successfully fabricated bioSiC from Sipo wood and studied the kinetics of Si removal by wet etching. The results suggest that the reaction is diffusion-limited, and the etch rate follows a t−0.5 law. The etching rate is found to be anisotropic, which can be explained attending to the anisotropy of the pore distribution. The compressive strength was studied as a function of etching time, and the results show a quadratic dependence with density. In the attainable range of densities, the strength is similar or better than that of human bone.

We have investigated the polarity of zinc oxide (ZnO) and Al-doped ZnO films grown on (11¯20) and (0001) sapphire substrates, using coaxial impact collision ion scattering spectroscopy. The films grown by pulsed laser deposition with a nominally undoped ZnO ceramic target had a (000¯1) surface, whereas the films prepared with a 1 mol% Al-doped ZnO ceramic target had a (0001) surface. The usage of Al-doped and undoped targets caused no difference in the in-plane lattice orientation. Electron microscope observations revealed that polarity change due to doping occurred without the formation of any interfacial phase between ZnO and sapphire.

Fundamental processes of wear include the rupture of single chemical bonds and the displacement of atoms or small clusters by mechanical action. Experimental studies of such processes have become feasible with the development of scanning probe microscopy. The small volume affected in these experiments overlaps with the size scale of large atomistic simulations, making a direct comparison possible. The complexity of real-world wear processes is reduced in most nanometer-scale experiments, for example, by probing surfaces of single crystals or by establishing and maintaining carefully controlled environments, including ultraclean conditions. The studies address the onset and topography of wear, the formation of debris structures, the interplay of mechanical and chemical action, the role of ultrathin films, the role of crystal defects in wear processes, and temporal and thermal effects.

Commercial Zr44Ti11Cu10Ni10Be25 bulk metallic glass (Vitreloy 1b) disk was subjected to extreme plastic deformation by high-pressure torsion at room temperature. Two-dimensional mapping by high-intensity synchrotron x-ray diffraction in the plane of the shear deformation reveals no evidence of nanocrystallization; however, average effective volume changes as a function of the deformation can be evaluated.

I’ve long been suspicious about attempts to see energy as the overwhelmingly central item setting both options and criteria for design in nature. Indeed, when I tried to create a conceptual framework for teaching biology to college students, I ended up putting energy distinctly second to information. Where energy rules, one can find some analog of voltage potential. But in nature, who eats whom boils down to the design and operation of one’s particular teeth and other equipment. I once set up an electrical analog of an ecosystem, but it gave an unreasonable picture until I added ad hoc diodes to keep the trees from eating the caterpillars at night and other such misbehavior. (Steve Vogel, Duke University, 2007)

In materials processing, Nature replaces the massive use of energy (for example high temperatures or harsh chemical reactions) with the use of information (which equates with structure at all levels, molecule to ecosystem). Indeed, most of the exceptional functionality of biological materials is due to their complex structure, driven by their chemical composition and morphology derived from DNA. It is here that the most important aspect of biomimetics emerges, and it has the power to redesign engineering.

Microstructure evolution of YBa2Cu3O7−y (YBCO) films during the two heat-treatments in the advanced trifluoroacetates metalorganic deposition (TFA-MOD) process has been investigated by means of transmission electron microscopy. In the calcination process, precursor films including nanopores were formed through the shrinkage of the film after a remarkable increase of the thickness due to the thermal decomposition of metalorganic salts in the starting solution. During the crystallization process, the densification and shrinkage of the film occurred after agglomeration of nanopores and coarsening of unreacted phase particles such as Y2Cu2O5, CuO, and Ba–O–F in the precursor films. The YBCO films were then epitaxially grown with the remaining unreacted phase particles in the film, finally pores were generated again by a reaction of these unreacted particles to form YBCO accompanied by the volume reduction. It is important to control the densification of precursor films and coarsening of the unreacted phase particles in the crystallization process, to fabricate YBCO final films with fine crystallinity and high critical current values.

Biomimetic layer-by-layer (BioLBL) is a layering method in which the binding and mineralization activities of a peptide aptamer are alternately used to accumulate layers of aptamer-displaying nanomaterials and thin mineral strata. We previously demonstrated this in aqua nanofabrication with BioLBL using a recombinant ferritin that displays an aptamer for titanium (minTBP-1) [K. Sano et al.: J. Am. Chem. Soc. 128, 1717 (2006); K. Sano et al.: Nano Lett.7, 3200 (2007)]. To expand the versatility of BioLBL, here we prepared a modified ferritin that was chemically ornamented with minTBP-1 and showed that BioLBL enables the formation of multiple layers of the chemically modified ferritin in a stepwise manner.

Reactions of molten Sn–xCu (x = 0.05 to 1.0) alloys with Te substrate at 250 °C were investigated. A dosage of 0.1 wt% Cu in Sn is found to be effective in suppressing the vigorous Sn/Te reaction by forming a thin CuTe at the solder/Te interface. The CuTe morphology changes from irregular clusters into a layered structure with increasing Cu content in Sn. With the same reaction time, the CuTe thickness increases proportionally to the square root of Cu content in Sn–Cu alloys, suggesting a diffusion-controlled growth for CuTe.

There is increasing observational evidence for an implication of the order of interfacial water layers in biology, for instance in processes of cellular recognition and during first contact events, where cells decide to survive or enter apoptosis. Experimental methods that allow access to the order of interfacial water layers are thus crucial in biomedical engineering. In this study, we show that interfacial water structures can be nondestructively analyzed on the nanocrystalline diamond. Results open the gate to a new chapter in the design of biomaterials inspired by biomimetic principles.

Previous work on YBa2Cu3O7−x (YBCO) + BaSnO3 (BSO) films with a single composition showed significant critical current density (Jc) improvements at higher fields but lowered Jc in low fields. A detailed study on BSO concentrations provided here demonstrates that significant Jc enhancement can occur even up to 20 mol% BSO inclusion, where typical particulate inclusions in these concentrations degrade the YBCO performance. YBCO + BSO films were processed on (100) LaAlO3 substrates using premixed targets of YBa2Cu3O7-x (YBCO) with additions of 2, 4, 10, and 20 mol% BSO. The critical transition temperature Tc of the films remained high (>87 K), even with large amounts (20 mol%) of BSO. YBCO + BSO films showed a gradual increase in Jc at high fields as the amount of BSO was increased. More than an order of magnitude increase in Jc was measured in YBCO + BSO samples as compared to regular YBCO at 4 T. YBCO + 10 mol% BSO films showed overall improvement at all the field ranges while YBCO + 20 mol% BSO was better only at high fields. Transmission electron microscopy revealed the presence of ∼7–8-nm-diameter BSO nanocolumns, the density of which increased with increasing BSO content correlating well with the observed improvements in Jc.

The primary role of a lubricant is to control the friction and wear of rubbing surfaces to optimize the operation of a component by forming an interfacial film separating the surfaces. Lubrication research seeks to develop new lubricant formulations and to optimize component life and performance. To do this, we must understand the mechanisms of film formation and film properties and the way these relate to operating conditions. In many engineering components, the lubricant film is subjected to severe mechanical and thermal stresses as it passes through the loaded zone. These severe conditions can result in molecular alignment or conformational change and the formation of new chemical species, which will impact the lubrication performance of the fluid. The lubricant response within the contact is often transient and thus has proved difficult to study by conventional surface analytical methods. One alternative is to replace one of the surfaces by a transparent window and use molecular microspectroscopy (infrared or Raman) to analyze the film within the contact zone formed during rubbing. This article reviews the development and application of in-contact molecular spectroscopy for the study of lubricant properties within the rubbing interface for both conventional and biolubrication systems. This technique has been used to study molecular conformation, chemical composition, and pressure distribution in the high-pressure region of the contact zone. However, challenges remain, including detecting very thin films, obtaining depth profile information, and applying these methods more generally to biotribology.