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The microstructure of additively manufactured Ti-6Al-4V (Ti64) produced by a laser powder bed fusion process was studied during post-build heat treatments between 1043 K (770 °C) and just above the β transus temperature 1241 K (1008 °C) in situ using high-energy X-ray diffraction. Parallel studies on traditionally manufactured wrought and annealed Ti64 were completed as a baseline comparison. The initial and final grain structures were characterized using electron backscatter diffraction. Likewise, the initial texture, dislocation density, and final texture were determined with X-ray diffraction. The evolution of the microstructure, including the phase evolution, internal stress, qualitative dislocation density, and vanadium distribution between the constituent phases were monitored with in situ X-ray diffraction. The as-built powder bed fusion material was single-phase hexagonal close packed (to the measurement resolution) with a fine acicular grain structure and exhibited a high dislocation density and intergranular residual stress. Recovery of the high dislocation density and annealing of the internal stress were observed to initiate concurrently at a relatively low temperature of 770 K (497 °C). Transformation to the β phase initiated at roughly 913 K (640 °C), after recovery had occurred. These results are meant to be used to design post-build heat treatments resulting in specified microstructures and properties. [ABSTRACT FROM AUTHOR]

Three new collagen mimetic peptides containing the CLK motif as anchoring arms were tested for silver nanoparticle surface stabilization. Our experimental and molecular dynamics data indicate that peptide length has an important effect not only in the resulting nanosilver's colloidal stability, but also in the biological performance of the composite. [ABSTRACT FROM AUTHOR]

[Display omitted] • Volume fraction of stress-induced martensite detected in coarse grained NiTi decreases continuously towards zero with increasing temperature. • Ductility and deformation induced by localized martensitic transformation in coarse grained NiTi do not increase monotonously with temperature. • High density of austenite {1 1 4} deformation twins were identified in plastically deformed microstructure of coarse grained NiTi. • Martensite desist temperature is indicated by transition from localized to homogeneous tensile deformation. In this work, effects of temperature and microstructure on tensile behavior of superelastic NiTi wires were analyzed. We analyzed cold-drawn NiTi wires of 1.78 mm that received four different final heat treatments using short direct electrical current pulses. Final coarse-grained microstructures ranged from recovered up to fully recrystallized microstructure with grain size of 25 µm. Effects of temperature in the range 30–130 °C were analyzed using monotonous tensile tests where a temperature gradient was induced along the sample axis. Deformation processes related to martensitic transformation and plastic deformation were characterized by temperature resolved stress–strain responses, deformation work, released heat, volume fraction of martensite. Deformation-induced microstructure changes were analyzed post-mortem using Electron Backscatter Diffraction and x-ray diffraction. Except the least recovered microstructure, the samples did not follow linear temperature trends according to Clausius-Clapeyron. With increasing temperature, the plateau stress of localized martensitic transformation stabilized at a constant stress while volume fraction of martensite decreased down to zero. Localized strains induced by martensitic transformation and ductility evolved non-monotonously with temperature, reaching maxima at temperatures that decreased with increasing microstructure recovery or recrystallization. Large ductility was positively correlated with occurrence of austenite deformation twins in deformed microstructure. [ABSTRACT FROM AUTHOR]

The cornea is the transparent front part of the eye that transmits light to the back of the eye to generate vision. Loss of corneal transparency, if irreversible, leads to severe vision loss or blindness. For decades, corneal transplantation using human donor corneas has been the only option for treating corneal blindness. Despite recent improvement in surgical techniques, donor cornea transplantation remains plagued by risks of suboptimal optical results and visual acuity, immune rejection and eventually graft failure. Furthermore, the demand for suitable donor corneas is increasing faster than the number of donors, leaving thousands of curable patients untreated worldwide. Here, we critically review the state of the art of biomaterials for corneal regeneration. However, the lessons learned from the use of the cornea as a disease model will allow for extension of the biomaterials and techniques for regeneration of more complex organs such as the heart. [ABSTRACT FROM AUTHOR]

In this study, we derivatized type I collagen without altering its triple helical conformation to allow for facile hydrogel formation via the Michael addition of thiols to methacrylates without the addition of other crosslinking agents. This method provides the flexibility needed for the fabrication of injectable hydrogels or pre-fabricated implantable scaffolds, using the same components by tuning the modulus from Pa to kPa. Enzymatic degradability of the hydrogels can also be easily fine-tuned by variation of the ratio and the type of the cross-linking component. The structural morphology reveals a lamellar structure mimicking native collagen fibrils. The versatility of this material is demonstrated by its use as a pre-fabricated substrate for culturing human corneal epithelial cells and as an injectable hydrogel for 3-D encapsulation of cardiac progenitor cells. [ABSTRACT FROM AUTHOR]

With in situ nanocompression experiments in a transmission electron microscope, we investigated plastic deformation in natural quartz crystals and observed both dislocation plasticity as well as mechanical twinning. Through this experimental method, we are able to provide direct evidence of Dauphiné twin nucleation and could measure the intrinsic twinning stress. The twinning phenomena appear to include a memory effect, where the same twin can reappear upon successive loading and unloading events. The data provide insight into this twin generation mechanism and can be used as a benchmark for the use of twins in quartz for paleopiezometry. Together, the observation of room-temperature dislocation plasticity and reversible twinning adds new insight into the extensive field of quartz plasticity and demonstrates the usefulness of small-scale testing techniques for mineral physics. [ABSTRACT FROM AUTHOR]

Resonant Inductive Coupling (RIC) Wireless Power Transfer is a key technology to provide an efficient and harmless wireless energy channel to consumer electronics, biomedical implants and wireless sensor networks. However, there are two factors that are limiting the applicability of this technology: the effects of distance variation between transmitter and receiver and the effects of interfering objects. While distance variation in WPT has been thoroughly studied, the effects of conductive interfering objects in resonant inductive coupling links are still unclear. When a conductive element is in the vicinity of a RIC link, both the transmitter and the receiver can experiment a change on their resonant frequencies as well as their impedances. This can greatly affect the efficiency of such WPT link causing it to a) make the transmitter and/or receiver act as a pass-band filter and b) loose part of the transmitter magnetic field through coupling to the interfering object. Depending on the natural resonant frequency of the object and the distances between this object and the transmitter and receiver antennas, this can affect significantly the RIC wireless power transfer link. In this article, we characterize the Magnetic behavior of a resonant inductive coupled link in the presence of a conductive interfering object using a Finite Element Field Solver (FEKO). Several distances between interference and transmitter/receiver are analyzed providing a design space exploration and applicability study of this link. [ABSTRACT FROM AUTHOR]