Indium tin oxide (ITO) has become a very useful plasmonic and nonlinear optical material because of its highly tunable electrical and optical properties and strong optical nonlinearity. In this work, the authors conducted detailed fabrication process studies by using high-temperature reactive sputtering to finely tune the optical properties of ITO thin films, particularly the epsilon-near-zero (ENZ) wavelength in the near and mid-IR spectrum. Sputtered ITO thin films are characterized by using spectroscopic ellipsometry, surface profilometry, Hall measurements, and 4-point probe testing. Additionally, the effect of post-deposition annealing of ITO films is also investigated.

Inspired by the recently reported translucency of monolayer graphene (GE) to wetting, atomistic simulations are employed to evaluate water flow enhancement induced by GE deposited on the inner surfaces of hydrophilic nanochannels. The flow in the coated channels exhibits a slip length of approximately 3.0 nm. Moreover, by contrasting the flow rates in channels with coated walls against flow rates in the corresponding uncoated channels, an “effective” flow enhancement from 3.2 to 3.7 is computed. The probability density function of the water dipole orientation indicates that the flow enhancement is related to a thinner structured water layer at the solid–liquid interface. This study provides quantitative evidence that GE employed as coating reduces substantially hydraulic losses in hydrophilic nanoconfinement.

The authors design six alumina hybrid structures consisting of stretching-dominated plates and different space-filling lattices comprised of hollow tubes and perform finite element simulations to study mechanical and failure behaviors of such hybrid structures. The authors investigate the effects of three geometrical parameters on the stiffness and failure of these hybrid structures and further compare their advantages and disadvantages. The authors find that the failure modes of these hybrid structures can be tuned by altering cell unit type and geometrical parameters. Among these hybrid structures, the ones with effective support from the lattice unit cells in the stretching direction exhibit better specific stiffness and strength. By varying the lattice and plate thickness, the authors find that the relations between stiffness/failure strength and density follow a power law. When intrinsic material failure occurs, the power law exponent is 1; when buckling failure arises, the power law exponent is 3. However, by varying tube thickness, their relations follow unusual power relations with the exponent changing from nearly 0 to nearly infinity. In addition, the hybrid structures also exhibit defect insensitivity. This study shows that such hybrid structures are able to greatly expand the design space of architectured cellular materials for engineering applications.

The generalized gradient approximation (GGA) often fails to correctly describe the electronic structure and thermochemistry of transition metal oxides and is commonly improved using an inexpensive correction term with a scaling parameter U. The authors tune U to reproduce experimental vanadium oxide redox energetics with a localized basis and a GGA functional. The value for U is found to be significantly lower than what is generally reported with plane-wave bases, with the uncorrected GGA results being already in reasonable agreement with experiments. This computational set-up is used to calculate interstitial and substitutional insertion energies of main group metals in vanadium pentoxide and interstitial doping is found to be thermodynamically favored.

Sample geometry effects on mechanical strengths of gold micro-cantilevers are evaluated by a micro-bending test. Six micro-cantilevers with the same length of 50 μm are prepared, and the width and the thickness are varied to examine individual effects on the yield stress. The yield stress increases from 428 to 519 MPa when the thickness decreases from 11.1 to 6.0 μm. No obvious dependency is observed when varying the width. The results reveal that the thickness and the width each has a different influence on the yield stresses of micro-cantilevers evaluated by the bending test, which is the sample geometry effect.

This study investigated a new strategy for fabricating porous scaffolds with the self-folding ability and controlled release of growth factors (GFs) via 3D printing. The scaffolds were a bilayer structure comprising a poly(D,L-lactide-co-trimethylene carbonate) scaffold for providing the shape morphing ability and a gelatin methacrylate scaffold for encapsulating and delivering GF. The structure, shape morphing behavior, GF release, and its effect on stem cell behavior were studied for new scaffolds. The results suggest that these scaffolds have great potential for regenerating tissues such as blood vessels. This work also contributes to developments of 3D printing in tissue engineering.

Engineering of thermoelectric materials requires an understanding of thermal conduction by lattice and electronic degrees of freedom. Filled skutterudites denote a large family of materials suitable for thermoelectric applications where reduced lattice thermal conduction attributed to localized low-frequency vibrations (rattling) of filler cations inside large cages of the structure. In this work, a multi-wavelength method of exploiting x-ray dynamical diffraction in single crystals of CeFe4P12 is presented and applied to resolve the atomic amplitudes of vibrations. The results suggest that the vibrational dynamics of the whole filler-cage system is the actual active mechanism behind the optimization of thermoelectric properties.

Inflammation is facilitated largely by macrophages and other white blood cells, which recognize and respond to evolutionarily conserved damage-associated molecular patterns that are released upon tissue injury and cell stress. Damage-associated molecular patterns are known to bind Toll-like receptors (TLRs) and initiate inflammatory responses through MyD88-dependent NF-κB signaling. Biomaterial implantation activates the innate immune system, resulting in a chronic inflammatory response known as a foreign body reaction (FBR). In this review, the authors discuss the current understanding of damage-initiated TLR signaling in the FBR and the significance of this response in the success of implanted devices.

Barium titanate (BTO) is a ferroelectric perovskite with potential in energy storage applications. Previous research suggests that BTO dielectric constant increases as nanoparticle diameter decreases. This report recounts an investigation of this relationship. Injection-molded nanocomposites of 5 vol% BTO nanoparticles incorporated in a low-density polyethylene matrix were fabricated and measured. Finite-element analysis was used to model nanocomposites of all BTO sizes and the results were compared with experimental data. Both indicated a negligible relationship between BTO diameter and dielectric constant at 5 vol%. However, a path for fabricating and testing composites of 30 vol% and higher is presented here.

The photothermal experiments on the incident light angle dependence are carried out using simulated solar light on thin films of both iron oxides (Fe3O4 and Fe3O4@Cu2-xS) and porphyrin compounds (chlorophyll and chlorophyllin). Fe3O4 and Fe3O4@Cu2-xS are synthesized using various solution methods that produce mono-dispersed nanoparticles on the order of 10 nm. Chlorophyll is extracted from fresh spinach and chlorophyllin sodium copper is a commercial product. These photothermal (PT) materials are dispersed in polymethyl methacrylate (PMMA) solutions and deposited on glass substrates via spin coating that result in clear and transparent thin films. The iron-oxide based thin films show distinctive absorption spectra; Fe3O4 exhibits a strong peak near UV and gradually decreases into the visible and NIR regions; the absorption of Fe3O4@Cu2-xS is similar in the UV region but shows a broad absorption in the NIR region. Both chlorophyll and chlorophyllin are characterized with absorption peaks near UV and NIR showing a “U”-shaped spectrum, ideally required for efficient solar harvest and high transparency in energy-efficient single-pane window applications. Upon coating of the transparent PT films on the window inner surfaces, solar irradiation induces the photothermal effect, consequently raising the film temperature. In this fashion, the thermal loss through the window can be significantly lowered by reducing the temperature difference between the window inner surface and the room interior, based on a new concept of so-called optical thermal insulation (OTI) without any intervention medium, such as air/argon, as required in the glazing technologies. Single-panes are therefore possible to replace double- or triple panes. As OTI is inevitably affected by seasonal and daily sunlight changes, an incident light angle dependence of the photothermal effect is crucial in both thin film and window designs. It is found that the heating curves reach their maxima at small angles of incidence while the photothermal effect is considerably reduced at large angles. This angle dependence is well explained by light reflection by the thin film surface, however, deviated from what is predicted by the Fresnel's law, attributable to non-ideal surfaces of the substrates. The angle dependence data provide an important reference for OTI that window exposure to the sun is greater at winter solstice while that is considerably reduced in the summer. This conclusion indicates much enhanced solar harvesting and heat conversion via optically insulated windows in the winter season, resulting in much lower U-factors.

Here, the authors report a detailed method of growing LaAlGe, a nonmagnetic Weyl semimetal, thin film on silicon(100) substrates by molecular beam epitaxy and their structural and electrical characterizations. About 50-nm-thick LaAlGe films were deposited and annealed for 16 h in situ at a temperature of 793 K. As-grown high-quality films showed uniform surface topography and near ideal stoichiometry with a body-centered tetragonal crystal structure. Temperature-dependent longitudinal resistivity can be understood with dominant interband s–d electron–phonon scattering in the temperature range of 5–40 K. Hall measurements confirmed the semimetallic nature of the films with an electron-dominated charge carrier density of ~7.15 × 1021 cm−3 at 5 K.

The development of flexible, stretchable, conformal electronics, and smart textiles for wearables and other applications by now lacks a guidance toward environmentally benign product concepts. This article facilitates understanding of environmental implications of material choices and design decisions to help material scientists and product developers alike to consider sustainability implications of their research, innovation, and development. The more such electronics enter the market, the more these composite products will emerge as an ecological problem, unless appropriate measures are taken at the early research stage.

Impedance spectroscopy was conducted on colloidal ITO thin films that had been subjected to alternating oxygen and argon plasma treatments, followed by air annealing from 150 to 750 °C. An equivalent circuit consisting of an RC element nested within another RC element, featuring a negative resistance and a negative capacitance, fitted the data well. These results are interpreted as being due to surface plasmons that are a function of the presence of nanoporous ITO-rich regions surrounded by isolated ITO nanoparticles coated with an amorphous polymer that intertwines with the ITO-rich regions as a function of annealing treatment.

Tracing the flow of solid matter during an explosion requires a rugged tag that can be measured by a unique identifiable signature. Silica-covered semiconductor quantum dots (QDs) provide a unique and tunable photoluminescent signature that emits from within a sacrificial outer layer. Five types of silica-covered zinc sulfide QDs were synthesized and covalently bound to commercial luminescent powders. The combination of five dots and five powders enables a matrix of 25 unique tags. The tracers are shown to be tolerant of environments associated with chemical explosives and provides a unique tag to evaluate debris fields.

Gravity is commonly considered negligible when the surface tension is dominant; i.e., the Bond number is less than 1. In this paper, however, the authors present a technique in which drops slide over surfaces with zero effective gravity. Our study compared the sliding motion of water drops on hydrophilic and hydrophobic surfaces in scenarios: one in which effective gravity = 1 (1 g) and one in which it = 0 (0 g). The authors found that the lateral retention force was greater under 1 g than it was under 0 g. Also, the results showed that retention forces calculated by Furmidge equation are higher than the measured forces.

Three-dimensional cultures have exciting potential to mimic aspects of healthy and diseased brain tissue to examine the role of physiological conditions on neural biomarkers, as well as disease onset and progression. Hypoxia is associated with oxidative stress, mitochondrial damage, and inflammation, key processes potentially involved in Alzheimer's and multiple sclerosis. We describe the use of an enzymatically-crosslinkable gelatin hydrogel system within a microfluidic device to explore the effects of hypoxia-induced oxidative stress on rat neuroglia, human astrocyte reactivity, and myelin production. This versatile platform offers new possibilities for drug discovery and modeling disease progression.

To investigate the manipulation of electromagnetic properties of two-dimensional materials, this effort characterizes charge transfer behavior of colloidal COF-5 (covalent organic framework) in the presence of various metal ions. A series of metal chloride compounds was introduced to COF-5 in solution and solid film phases and the interaction of the material with electromagnetic radiation was monitored across the visible region using electronic absorption spectroscopy. Notable changes were observed, quantified, and discussed for copper (II) chloride (CuCl2), chromium (III) chloride (CrCl3), and iron (III) chloride (FeCl3) with COF-5. Ligand-to-metal and metal-to-ligand charge transfer are explored as a possible mechanism for the observed electronic behaviors.

Material changes in yttrium-doped barium zirconate, BaZr0.8Y0.2O3–x, were studied using in situ Raman spectroscopy and ex situ x-ray photoelectron spectroscopy analysis. During in situ Raman analysis, samples were heated to temperatures of 300–600 °C and exposed to both dry and humidified H2 atmospheres. At the lower temperatures (300–450 °C), a new vibrational peak appears in the Raman spectra during exposure to humidified H2. The appearance of this feature is reversible, dependent on previous sample history, and possibly results from new, secondary phase formation or lattice distortion.

The authors demonstrate that multicomponent metallic alloy nanofoams can be synthesized by the polymeric templating method. The present approach enabled alloy compositions not accessible via commonly used dealloying or co-deposition methods. The authors report the synthesis of a Cu50Ni50 alloy nanofoam using electrospinning polymeric templating, which exhibits distinct polycrystallinity, process-driven segregation, and enhanced mechanical strength over pure Cu nanofoams. Transmission electron microscopy revealed microscopic grain formation and their variable compositions. The processing method is applicable to the synthesis of a wide range of multicomponent metal porous materials, creating new research opportunities for noble alloy foams not available through wet electrochemical routes.

This work investigated the photophysical pathways for light absorption, charge generation, and charge separation in donor–acceptor nanoparticle blends of poly(3-hexylthiophene) and indene-C60-bisadduct. Optical modeling combined with steady-state and time-resolved optoelectronic characterization revealed that the nanoparticle blends experience a photocurrent limited to 60% of a bulk solution mixture. This discrepancy resulted from imperfect free charge generation inside the nanoparticles. High-resolution transmission electron microscopy and chemically resolved X-ray mapping showed that enhanced miscibility of materials did improve the donor–acceptor blending at the center of the nanoparticles; however, a residual shell of almost pure donor still restricted energy generation from these nanoparticles.