Designing advanced nonprecious metal electrocatalysts to reduce overpotential and accelerate hydrogen evolution reaction (HER) has attracted considerable attention. However, improving the sluggish kinetics for electrocatalytic HER in alkaline media is still a great challenge. Herein, we found that amorphous NiO nanoclusters directly grown on nickel foam (NiO/NF) as a bifunctional HER catalyst demonstrated an ultrahigh electrocatalytic activity in alkaline environment. Such excellent HER performance of NiO/NF might mainly originate from the exposed interfaces of metallic Ni and amorphous NiO. The coordinatively unsaturated amorphous NiO domain is propitious to the adsorption of water molecule and the successive cleavage of HO–H bond, while the neighboring metallic Ni domain is beneficial to the adsorption of resulting Hads intermediate and recombination into hydrogen molecules, thus expediting the HER toward lower overpotential. These findings may open a window to the design and preparation of earth-abundant, low-cost metal oxide/metal electrocatalysts with desirable HER activities.

Chronic osteomyelitis, a bone infection caused by bacteria, requires extensive parenteral treatments. With an aim to develop bioactive glass with antibacterial properties to resist such infections, bioactive glasses with bismuth oxide as the dopant in various amounts up to 8 wt% were prepared. X-ray diffraction patterns and Fourier-transform infrared spectra of glass samples after immersion in simulated body fluid showed the presence of hydroxyapatite (HAp) and hydroxyl carbonate apatite for all samples except with the one having Bi2O3 substitution of 8 wt%. In vitro cell proliferation by MTT assay studies using a mouse fibroblast cell line (NIH3T3) have also been carried out. Primary antimicrobial activity of the glass particles was analyzed against Escherichia coli (E. coli) using broth microdilution method which exhibited bacteriostatic effects and bactericidal properties in selected samples. The combination of bioactivity, cell proliferation, and antibacterial properties of selected Bismuth-containing bioactive glasses could be exploited in treating bone-related infections.

To secure the reliability of flexible electronics, the effect of multicomponent stress on the device properties during complex mechanical deformation needs to be thoroughly understood. The electrical resistances of metal interconnects are investigated by in situ monitoring at different twisting angles and with different pattern positions. As the twisting angle increased, the electrical resistance increased earlier. Furthermore, in the line pattern located far from the central axis, severe electrical degradation and fatigue damage formation were observed. Multicomponent stress evolution during twisting was analyzed by the finite-element simulation method. For easy practical application for estimating the representative twisting strain, an analytic solution of twisting deformation was formulated and compared with the simulation. Using the equivalent strain, the fatigue lifetime was fitted, and the exponents were obtained for lifetime expectation. This systematic study provides the guidelines for highly reliable flexible devices and the tools for determining the expected fatigue lifetime.

The combined effect of B2 phase transfer and grain boundary character on mechanical properties of the Fe–6.5 wt% Si alloy was investigated. The microstructures and textures of the Fe–6.5 wt% Si alloy under four cooling modes were characterized by X-ray diffraction, transmission electron microscope, and electron backscattered diffraction. The results reveal that the maximum nano-hardness value (8.9 GPa) results from the two-step air-cooling sample, while for the two-step water-cooling sample, the minimum value (5.3 GPa) is achieved. The transformation of the B2 phase affected by the water-cooling process is a critical factor in obtaining the lower APB energy and eliminating the brittlenes. A large fraction of the coincidence site lattice boundaries that formed on the sheet experienced the two-step water-cooling process due to a uniform and sharp γ-fiber recrystallization texture comprising the {111} 〈110〉 and {111} 〈112〉 components, which enhances resistance to intercrystalline effect and improves mechanical properties in comparison with the two-step air-cooling process.

Fatigue cracking in polycrystalline NiTi was investigated using a multiscale experimental framework for average grain sizes (GS) from 10 to 1500 nm for the first time. Macroscopic fatigue crack growth rates, measured by optical digital image correlation, were connected to microscopic crack opening and closing displacements, measured by scanning electron microscope DIC (SEM-DIC) using a high-precision external SEM scan controller. Among all grain sizes, the 1500 nm GS sample exhibited the slowest crack growth rate at the macroscale, and the largest crack opening level (stress intensity at first crack opening) and minimum crack opening displacements at the microscale. Smaller GS samples (10, 18, 42, and 80 nm) exhibited nonmonotonic trends in their fatigue performance, yet the correlation was strong between macroscale and microscale behaviors for each GS. The samples that exhibited the fastest crack growth rates (42 and 80 nm GS) showed a small crack opening level and the largest crack opening displacements. The irregular trends in fatigue performance across the nanocrystalline GS samples were consistent with nonmonotonic values in the elastic modulus reported previously, both of which may be related to the presence of residual martensite only evident in the small GS samples (10 and 18 nm).

First principles was carried out studying the properties of (Ti, Nb)C compounds based on density functional theory. The integration of mechanical behavior, electronic structures, and thermodynamic properties can be optimized by mediating the concentration of the titanium alloying element. The results revealed that these transition metal compounds were stable with the negative formation energy. Nb0.5Ti0.5C (29.15 GPa) demonstrated the largest hardness characterized by moduli (B, G) because of the stable shell configuration. NbC exhibited the strongest anisotropy from the universal anisotropic index (A U) and three-dimensional surface contours. Tix Nb1−x C compounds displayed relatively strong stress responses along the [001], [110], and [111] directions. Due to the weakening p–d bonding, the ideal tensile strength gradually decreased with the increasing titanium concentration. The electronic structures revealed that the bonding characteristics of the (Ti, Nb)C compounds were a mixture of metallic and covalent bonds. On the other hand, NbC and TiC exhibited a minimum (740.55 K) and maximum (919.29 K) Debye temperature, indicating the stronger metalic bonds of NbC and covalent bonds of TiC.

DNA nanostructures are a set of materials with well-defined physical, chemical, and biological properties that can be used on their own or incorporated with other materials for many applications. Herein, the practical aspects of utilizing DNA nanostructures (structural or dynamic) as materials are comprehensively covered. This article first summarizes properties of DNA molecules and practical considerations and then discusses the fundamental design principles of structural DNA nanostructures. Finally, various aspects of dynamic DNA nanostructure-based actuation and computation are included.

Materials used in wearable and implantable electronic devices should match the mechanical properties of biological tissues, which are inherently soft and deformable. In comparison to conventional rigid electronics, soft bioelectronics can provide accurate and real-time monitoring of physiological signals, improve comfort, and enable altogether new modalities for sensing. This article highlights recent progress, identifies technical challenges, and offers possible solutions for the emerging field of stretchable bioelectronics. We organize the content into three topical categories: (1) biological integration of soft electronic materials, (2) materials and mechanics, and (3) soft robotics. Finally, we conclude this article with a discussion on the outlook of the field and future challenges.

Structural DNA nanotechnology has been particularly driven toward three-dimensional (3D) construction since its inception at the start of the 1980s. Part of the driving force was the goal of building specific crystals from macromolecular components, without having to use trial and error for determining appropriate crystallization conditions. With the first demonstration of DNA attachment to gold nanoparticles in the 1990s, DNA became a player in inorganic nanomaterials as a programmable agent for structure assembly. For pure DNA structures, the crystallization goal has been mediated by sticky-ended cohesion with some success, although trial and error crystallizations have produced better diffracting crystals than those directed self-assembly. For nanoparticles, different types of 3D nanoscale crystalline organizations have been realized. Recent efforts not only expand the diversity of particle lattices, but also strive to achieve designed lattice symmetries and their transformations. In this article, we review the development of 3D assembly of DNA and DNA-guided nanoparticle arrays, the issues that have prevented and facilitated formation of such structures, and recent strategies toward this goal.

Structural DNA nanotechnology offers the capacity to construct ultraminiaturized devices with programmed nanoscale geometry, mechanical and dynamic properties, and site-specific molecular functionalities. These features and the possibility to position and orient molecules in user-defined ways may be exploited to create custom instruments for precision measurements of molecular-scale structure, dynamics, and interactions. Such devices may help constrain molecular motion along interesting reaction coordinates and may also exert forces to probe the mechanical properties or dynamics of molecules under study. Multiple ways of reading out device states may be used, including atomic force microscopy or transmission electron microscopy imaging, single-molecule or bulk fluorescence, or ionic conductivity as in nanopore systems. Early successes with custom scientific instruments based on DNA origami underline the tremendous potential to enable new approaches to making scientific discoveries in biological and synthetic materials systems.

RNA nanotechnology seeks to exploit the structural and functional properties of the RNA molecule in order to rationally design RNA nanoparticles and devices for applications in biotechnology and medicine, among others. Compared to DNA, RNA can adopt a larger diversity of structural motifs that allows the construction of more complicated nanoparticles that can be self-assembled during synthesis by the RNA polymerase—a process called co-transcriptional folding. RNA nanostructures can be genetically encoded and co-transcriptionally folded in cells, which allows large-scale production of RNA nanoparticles for therapeutic use or the application as scaffolds in cells for manipulating cellular components for use in synthetic biology. In this article, we describe the origins of the RNA nanotechnology research field and how it has been inspired by DNA nanotechnology. Recent developments of co-transcriptionally folded RNA nanostructures and the construction of RNA knots are discussed in relation to design principles and challenges, and speculations about future directions of the field are provided.