Polarization-driven reversible actuation in a photo-responsive polymer composite.

Light-responsive polymers and especially amorphous azopolymers with intrinsic anisotropic and polarization-dependent deformation photo-response hold great promises for remotely controlled, tunable devices. However, dynamic control requires reversibility characteristics far beyond what is currently obtainable via plastic deformation of such polymers. Here, we embed azopolymer microparticles in a rubbery elastic matrix at high density.

The effects of surface treatments on electron beam melted Ti-6Al-4V disks on osteogenesis of human mesenchymal stromal cells.

Additive manufactured (AM) Titanium-6Aluminum-4Vanadium (Ti64) scaffolds display unique mechanical and biological properties for implant devices. The elastic modulus can be tailored by adjusting the porosity, further facilitating bone ingrowth. Although Ti64 implants are biocompatible, the effects of AM surfaces without porous structures, and how the topography and surface chemistry of the respective surfaces affect the osteogenesis of bone marrow-derived mesenchymal stromal cells (BMSCs) has not yet been revealed.

Line-focus solar concentration 10 times higher than the 2D thermodynamic limit.

Line-focus solar concentrators have traditionally been limited by the 2D concentration limit due to the continuous translational symmetry in these systems. This limit is orders of magnitude lower than the 3D limit, severely limiting the achievable concentration ratio compared to point-focus systems. We propose a design principle for line-focus solar concentrators that bypasses this 2D limit, while maintaining a trough-like configuration and only requiring single-axis external solar tracking.

A toolbox for easy entry low wavenumber in situ atomic layer deposition transmission FTIR spectroscopy studies.

A detailed description of a flexible and portable atomic layer deposition (ALD) system is presented for conducting in situ Fourier transform infrared (FTIR) absorption spectroscopy studies during the evolution and growth of ALD films. The system is directly integrated with a commercial FTIR spectrometer (Bruker Vertex 80V) to avoid the necessity of an external optical path to the instrument, thereby mitigating complexity and optical losses. In this work, we use potassium bromide (KBr) with a 5 nm layer of sputtered Si as a substrate due to higher infrared transmittance when compared to a single-side polished Si wafer.

Revealing the influence of electron beam melted Ti-6Al-4V scaffolds on osteogenesis of human bone marrow-derived mesenchymal stromal cells.

Porous Titanium-6Aluminum-4Vanadium scaffolds made by electron beam-based additive manufacturing (AM) have emerged as state-of-the-art implant devices. However, there is still limited knowledge on how they influence the osteogenic differentiation of bone marrow-derived mesenchymal stromal cells (BMSCs). In this study, BMSCs are cultured on such porous scaffolds to determine how the scaffolds influence the osteogenic differentiation of the cells.

Direct Integration of Strained-Pt Catalysts into Proton-Exchange-Membrane Fuel Cells with Atomic Layer Deposition.

The design and fabrication of lattice-strained platinum catalysts achieved by removing a soluble core from a platinum shell synthesized via atomic layer deposition, is reported. The remarkable catalytic performance for the oxygen reduction reaction (ORR), measured in both half-cell and full-cell configurations, is attributed to the observed lattice strain. By further optimizing the nanoparticle geometry and ionomer/carbon interactions, mass activity close to 0.

Beyond the 2D limit: étendue-squeezing line-focus solar concentrators.

Line-focus solar concentrators are commonly designed by extruding a two-dimensional concentrator in the third dimension. For concentration in air, these concentrators are, by the nature of their design, limited by the two-dimensional solar concentration limit of 212×. This limit is orders of magnitude lower than the 45000× concentration limit for three-dimensional solar concentrators.

Publisher Correction: Conductivity control via minimally invasive anti-Frenkel defects in a functional oxide.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Conductivity control via minimally invasive anti-Frenkel defects in a functional oxide.

Utilizing quantum effects in complex oxides, such as magnetism, multiferroicity and superconductivity, requires atomic-level control of the material's structure and composition. In contrast, the continuous conductivity changes that enable artificial oxide-based synapses and multiconfigurational devices are driven by redox reactions and domain reconfigurations, which entail long-range ionic migration and changes in stoichiometry or structure. Although both concepts hold great technological potential, combined applications seem difficult due to the mutually exclusive requirements.

High-performance stationary solar tracking through multi-objective optimization of beam-steering lens arrays.

Beam-steering lens arrays enable solar tracking using millimeter-scale relative translation between a set of lens arrays. This may represent a promising alternative to the mechanical bulk of conventional solar trackers, but until now a thorough exploration of possible configurations has not been carried out. We present an approach for designing beam-steering lens arrays based on multi-objective optimization, quantifying the trade-off between beam divergence and optical efficiency.

The effect of Equal Channel Angular Pressing on the stress corrosion cracking susceptibility of AZ31 alloy in simulated body fluid.

Despite the great potential of Mg and its alloys as material for biodegradable implants, their low resistance to the simultaneous action of corrosion and mechanical stresses in the human body have hampered their use. Stress Corrosion Cracking has been reported as one of the most critical failure modes to overcome to allow such materials to be clinically applied. Thus, in this paper we investigate the effect of Equal Channel Angular Pressing (ECAP) on the Stress Corrosion Cracking (SCC) susceptibility of the AZ31 Mg alloy.

A Novel Approach for Assessing the Fatigue Behavior of PEEK in a Physiologically Relevant Environment.

In recent years, the need of surgical procedures has continuously increased and, therefore, researchers and clinicians are broadly focusing on the development of new biocompatible materials. Among them, polyetheretherketone (PEEK) has gained wide interest in load-bearing applications due to its yielding behaviour and its superior corrosion resistance. To assure its reliability in these applications where notches and other stress concentrators weaken implants resistance, a design tool for assessing its tensile and fatigue behaviour in the presence of geometrical discontinuities is highly claimed.

Rupture Predictions of Notched Ti-6Al-4V Using Local Approaches.

Ti-6Al-4V has been extensively used in structural applications in various engineering fields, from naval to automotive and from aerospace to biomedical. Structural applications are characterized by geometrical discontinuities such as notches, which are widely known to harmfully affect their tensile strength. In recent years, many attempts have been done to define solid criteria with which to reliably predict the tensile strength of materials.

Fatigue Behavior of Porous Ti-6Al-4V Made by Laser-Engineered Net Shaping.

The fatigue behavior and fracture mechanisms of additively manufactured Ti-6Al-4V specimens are investigated in this study. Three sets of testing samples were fabricated for the assessment of fatigue life. The first batch of samples was built by using Laser-Engineered Net Shaping (LENS) technology, a Direct Energy Deposition (DED) method.

Fracture Assessment of PEEK under Static Loading by Means of the Local Strain Energy Density.

Polyetheretherketone (PEEK) has gained interest in many industrial applications due to its high strength-to-weight ratio, excellent heat tolerance and high corrosion resistance. Stress concentrators such as notches and geometrical discontinuities are present in many such components necessitating the reliable assessment of notch sensitivity of PEEK in monotonic tension. Here we evaluate the applicability of the strain energy density (SED) approach for the assessment of the fracture strength of experimentally tested notched geometries subject to corrosion.

Revealing the Bonding Environment of Zn in ALD Zn(O,S) Buffer Layers through X-ray Absorption Spectroscopy.

Zn(O,S) buffer layer electronic configuration is determined by its composition and thickness, tunable through atomic layer deposition. The Zn K and L-edges in the X-ray absorption near edge structure verify ionicity and covalency changes with S content. A high intensity shoulder in the Zn K-edge indicates strong Zn 4s hybridized states and a preferred c-axis orientation.

ALD Zn(O,S) Thin Films' Interfacial Chemical and Structural Configuration Probed by XAS.

The ability to precisely control interfaces of atomic layer deposited (ALD) zinc oxysulfide (Zn(O,S)) buffer layers to other layers allows precise tuning of solar cell performance. The O K- and S K-edge X-ray absorption near edge structure (XANES) of ∼2-4 nm thin Zn(O,S) films reveals the chemical and structural influences of their interface with ZnO, a common electrode material and diffusion barrier in solar cells. We observe that sulfate formation at oxide/sulfide interfaces is independent of film composition, a result of sulfur diffusion toward interfaces.

Relating Electronic and Geometric Structure of Atomic Layer Deposited BaTiO3 to its Electrical Properties.

Atomic layer deposition allows the fabrication of BaTiO3 (BTO) ultrathin films with tunable dielectric properties, which is a promising material for electronic and optical technology. Industrial applicability necessitates a better understanding of their atomic structure and corresponding properties. Through the use of element-specific X-ray absorption near edge structure (XANES) analysis, O K-edge of BTO as a function of cation composition and underlying substrate (RuO2 and SiO2) is revealed.

Laser 3D printing with sub-microscale resolution of porous elastomeric scaffolds for supporting human bone stem cells.

A reproducible method is needed to fabricate 3D scaffold constructs that results in periodic and uniform structures with precise control at sub-micrometer and micrometer length scales. In this study, fabrication of scaffolds by two-photon polymerization (2PP) of a biodegradable urethane and acrylate-based photoelastomer is demonstrated. This material supports 2PP processing with sub-micrometer spatial resolution.

Laser photofabrication of cell-containing hydrogel constructs.

The two-photon polymerization (2PP) of photosensitive gelatin in the presence of living cells is reported. The 2PP technique is based on the localized cross-linking of photopolymers induced by femtosecond laser pulses. The availability of water-soluble photoinitiators (PI) suitable for 2PP is crucial for applying this method to cell-containing materials.

Photo-sensitive hydrogels for three-dimensional laser microfabrication in the presence of whole organisms.

Hydrogels are polymeric materials with water contents similar to that of soft tissues. Due to their biomimetic properties, they have been extensively used in various biomedical applications including cell encapsulation for tissue engineering. The utilization of photopolymers provides a possibility for the temporal and spatial controlling of hydrogel cross-links.