We report that a hexagonal closed-packed (HCP) phase with high cobalt content precipitates in Al0.5CoCrFeNi high entropy alloy (HEA) after 650 °C/8 h heat-treatment. The precipitate with the shape of plate is completely located at the interdendritic region. Results of electron diffraction and high resolution transmission electron microscopy show that the HCP phase was transformed from the body-centered cubic phase through a simple shear and the two phase obey an orientation relationship. The thermodynamic stability of Al0.5CoCrFeNi HEA should be carefully reevaluated, especially at the vulnerable temperature.

Several methods for determination of elastic–plastic parameters by instrumented spherical indentation tests have been presented in the past few years. Each method was established according to a specific constitutive model. Identification of the constitutive models of new materials has become an indispensable step in order to choose an appropriate indentation method to extract the elastic–plastic parameters. In the present work, the half depth energy accumulation rate and Meyer's index were related to the elastic–plastic constitutive models via qualitative and numerical analyses. A method for identification of the elastic–plastic constitutive models by instrumented spherical indentation test was proposed.

Angiogenesis is a critical component during wound healing, and the process is sensitive to mechanical stimuli. Current in vitro culture environments used to investigate three-dimensional microvascular growth often lack dimensional stability and the ability to withstand compression. We investigated the ability of decorin (DCN), a proteoglycan known to modulate collagen fibrillogenesis, incorporated into a collagen hydrogel to increase construct dimensional stability while maintaining vascular growth. DCN did not affect microvascular growth parameters, while increasing the compressive modulus of collagen gels and significantly reducing the contraction of 3% collagen gels after 16 days in culture.

Cellular activity upon osmotic stress is related to the occurrence of several disease conditions. The real-time monitoring of the cell response to this kind of stress can give insight into the comprehension of mechanisms involved in cellular shrinkage. Currently the dynamics of the osmotic stress is studied using dedicated and tricky methodologies, not suited to the in vivo testing. We show that a disposable electronic device is very effective for studying the early stage of the osmotic stress induced on human lung adenocarcinoma cells, A549, by a hyperosmotic environment. Our findings corroborate the experimental results obtained by a standard complementary analysis.

Bioengineered hydrogels enable systematic variation of mechanical and biochemical properties, resulting in the identification of optimal in vitro three-dimensional culture conditions for individual cell types. As the scientific community attempts to mimic and study more complex biologic processes, hydrogel design has become multi-faceted. To mimic organ and tissue heterogeneity in terms of spatial arrangement and temporal changes, hydrogels with spatiotemporal control over mechanical and biochemical properties are needed. In this prospective article, we present studies that focus on the development of hydrogels with dynamic mechanical and biochemical properties, highlighting the discoveries made using these scaffolds.

The magnetic and magnetocaloric properties of Ni45Mn43CoSn11 have been investigated using heat capacity measurements and magnetization with hydrostatic pressure applications. A shift in the martensitic transition temperature by 40 K to higher temperatures was observed with application of pressure P = 1.06 GPa. The magnetic entropy changes significantly increases from 24 to 42 J/kgK at pressure of 0.73 GPa. A large adiabatic temperature change of 4 K was found from specific heat measurements. Also, the density of states and Debye temperature has been estimated from heat capacity measurements. The mixed effects of pressure and magnetic field on the transition temperature are discussed.

First principles simulations and global optimization predict new mode of binding of Pt clusters with defects on graphene that significantly enhances their stability. Pt clusters were found to firmly bind to monovacancies in configuration transacting the vacancy site, while retaining the integrity of the cluster. Diffusion calculations support tight anchoring of Pt cluster to monovacancy. Pt cluster adsorbed on pristine graphene or other common defects exhibit a different mode of adsorption and only decorate one side of graphene. This study reveals strong influence of defect chemistry on the structure and mobility of Pt nanoclusters adsorbed on graphene and have important implications for catalytic and gas sensing applications.

In this study, we have developed a facile and simple route for preparation of ultrafine CoO/reduced graphene oxide (rGO) nanohybrids with tunable particle size and crystallinity for lithium-ion battery (LIB) application. At the optimized calcination time of 60 min, the homogeneous and ultrafine CoO nanoparticles with mean size of 4.5 nm can be intimately attached onto rGO surface to rapidly transport Li ions and electrons. The CoO/rGO exhibits excellent rate capability and high specific capacity of 520 mAh/g at 2400 mA/g. In addition, the capacity can be recovered to 900 mAh/g at 150 mA/g after 60 cycles, indicating the superior electrochemical performance of CoO/rGO for LIB applications.

A living electrode construct that enables integration of cells within bionic devices has been developed. The layered construct uses a combination of non-degradable conductive hydrogel and degradable biosynthetic hydrogel to support cell encapsulation at device surfaces. In this study, the material system is designed and analyzed to understand the impact of the cell carrying component on electrode characteristics. The cell carrying layer is shown to provide a soft interface that supports extracellular matrix development within the electrode while not significantly reducing the charge transfer characteristics. The living layer was shown to degrade over 21 days with minimal swelling upon implantation.

Lithium-ion capacitors utilizing graphite (G) and reduced graphite oxide (RGO) as negative electrode materials were investigated. Various reduction methods of graphite oxide were applied to compare properties of modified materials. The hybrid cells showed the energy density at mild current regimes of ca. 70–100 Wh/kg. However, at higher rates, only the capacitor with chemically RGO maintained this tendency. Moreover, the system demonstrated the energy density of 34 Wh/kg at a power density of 26 kW/kg. The electrochemical measurements were conducted in three-electrode systems to record responses of positive and negative electrodes separately.

We present an indentation-scope that interfaces with confocal microscopy, enabling direct observation of the three-dimensional (3D) microstructural response of coatings on substrates. Using this method, we compared microns-thick polymer coatings on glass with and without silica nanoparticle filler. Bulk force data confirmed the >30% modulus difference, while microstructural data further revealed slip at the glass-coating interface. Filled coatings slipped more and about two times faster, as reflected in 3D displacement and von Mises strain fields. Overall, these data indicate that silica-doping of coatings can dramatically alter adhesion. Moreover, this method compliments existing theoretical and modeling approaches for studying indentation in layered systems.

Cardiac progenitor cells (CPCs) are a promising candidate for cardiac regeneration, and the interaction between CPCs and their microenvironment can influence their regenerative response. Notch signaling plays a key role in cell fate decisions in the developing and adult heart. Here, we investigated the effect of three-dimensional (3D) spheroid culture, as a model of the 3D microenvironment, on Notch in fetal and adult human CPCs, under room air (20%) and physiological (5%) oxygen tension. Notch signaling is enhanced in 3D spheroids; spheroid culture under 5% O2 further increases Notch signaling enhancement, and might ultimately improve the regenerative potential of CPCs.

Human organoid models recapitulate many aspects of the complex composition and function of native organs. One of the main challenges in developing these models is the growth and maintenance of three-dimensional tissue structures and proper cellular organization that enable function. Biomaterials play an important role by providing a defined and tunable three-dimensional environment that is required for complex cellular organization and organoid growth in vitro or in vivo. This review summarizes organoids of the respiratory and digestive system, and the use of biomaterials to improve upon these model systems.

In this study, a comparison of the tensile behavior of fully nanotwinned Cu–6 wt.%Al, Cu–2 wt.%Al, and Cu–10 wt.%Ni with stacking fault energies (SFEs) of 6, 37, and 60 mJ/m2, respectively is presented. The samples displayed yield strengths ranging from 830 to 1340 MPa, varying with both alloy content and microstructural parameters. All samples showed low ductility, even though there are tilted twin boundaries present in Cu–10 wt.%Ni. The influence of varying grain width is presented for each alloy and related to both the activation volume and SFE [Figs. 3(a)–3(c)].

Functionalization of silicone rubber films with lysozyme was achieved by grafting copolymerization and its chemical activation allowing the covalent immobilization of the enzyme. The new materials were characterized by means of Fourier-transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, contact angle, atomic force microscopy, and mechanical properties of films. The enzymatic activity of films was studied by a suspension of lyophilized Micrococcus lysodeikticus. The activity test was inquired at different pH and temperatures, exhibiting enzymatic activity 20 °C above the free lysozyme, and at pH = 5 where the free lysozyme did not show activity.

Gelatin/poly(epichlorohydrin-co-ethylene oxide) [GL : PECO] composites are synthesized in a one-step process by the incorporation of elastic PECO and diclofenac. [GL : PECO] fibers are prepared by Forcespinning®. GL : PECO fibers are capable of diclofenac, by conjugation via a labile amide linkage. Fourier transform infrared spectroscopy (FTIR) results confirmed the chemical reactions and hydrogen bonds between gelatin, PECO, and diclofenac. Diclofenac drug release from GL : PECO fibers are measured for 15 days and prolonged drug release is observed. The cell viability is studied with NIH/3T3 and excellent results are observed. The sustained drug release and cytotoxicity results reveal that GL : PECO fibers could be promising substitutes for skin tissue engineering, wound healing, and drug delivery.

In vitro electrophysiology using microelectrode arrays (MEAs) plays an important role in understanding fundamental biologic processes, screening potential drugs and assessing the toxicity of chemicals. Low electrode impedance and ability to sustain viable cultures are the key technology requirements. We show that MEAs consisting of poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) and coated with poly-L-lysine satisfy these requirements. Hippocampal cell cultures, maintained for 3–6 weeks on these MEAs, give high quality recordings of neural activity. This enables the observation of drug-induced activity changes, which paves the way for using these devices in in vitro drug screening and toxicology applications.

LiFe1−xYxPO4 doped (d-LFP) with amounts of yttrium (0.01% < x < 5% w/w) show a remarkable effect on the electrochemical behavior. The d-LPF samples were investigated on the Li extraction/insertion performance through charge/discharge and capacity–voltage curves. The best performance was attained with Y content of x = 1%. The materials were synthesized by a hydrothermal method and characterized by x-ray diffraction (XRD) and scanning electron microscopy–energy dispersive x-ray spectroscopy (SEM–EDX). The XRD studies showed that d-LPF had the same monoclinic structure as the undoped material. The achieved electrode performance has been attributed to the addition of Y3+ ion by stabilizing the orthorhomic structure. The electrode resistance decreases through the Y-doping.

Pulsed electric current sintering offers rapid sintering of many materials compared with hot press sintering. Earlier studies had demonstrated that neither sparks nor plasma formation occur in a typical apparatus such as Dr. Sinter™. Hitchcock et al. showed that electromagnetic radio frequency (rf) emission occurred during the pulsing current and suggested this emission was a relevant augmentation to the hot press sintering in addition to the current flow in the specimen. In this report the importance of rf emission in the sintering process is demonstrated and opportunities to further exploit this approach to improve the sintering process are suggested.

We use a magnetothermal resistance method to measure the lattice thermal conductivity of single-crystal Bi2Te3 from 5 to 60 K. Lattice thermal conductivity is calculated by extrapolating the thermal conductivity versus electrical conductivity curve to a zero electrical conductivity value. Our results show that the measured phonon thermal conductivity follows the ${\rm e}^{{\it\Delta} _{{\rm min}}/T}$ temperature dependence and the Lorenz ratio corresponds to the modified Sommerfeld value in the intermediate temperature range. Our low-temperature experimental data and analysis on Bi2Te3 are a complement to previous measurements of Goldsmid (Ref. 17) and theoretical calculations by Hellman et al. (Ref. 18) at higher temperature 100–300 K.