Exceptionally strong, stiff and hard hybrid material based on an elastomer and isotropically shaped ceramic nanoparticles

Solvent controlled 2D structures of bottom-up fabricated nanoparticle superlattices

We demonstrate that oleyl phosphate ligand-stabilized iron oxide nanocubes as building blocks can be assembled into 2D supercrystalline mono- and multilayers on flat YSZ substrates within a few minutes using a simple spin-coating process. As a bottom-up process, the growth takes place in a layer-by-layer mode and therefore by tuning the spin-coating parameters, the exact number of deposited monolayers can be controlled. Furthermore, ex situ scanning electron and atomic force microscopy as well as X-ray reflectivity measurements give evidence that the choice of solvent allows the control of the lattice type of the final supercrystalline monolayers. This observation can be assigned to the different Hansen solubilities of the solvents used for the nanoparticle dispersion because it determines the size and morphology of the ligand shell surrounding the nanoparticle core. Here, by using toluene and chloroform as solvents, it can be controlled whether the resulting monolayers are ordered in a square or hexagonal supercrystalline lattice.

A smart magnetic hydrogel containing exosome promotes osteogenic commitment of human adipose-derived mesenchymal stem cells

Objectives

Exosomes, as nano-sized extracellular vehicles acting as cell-to-cell communicators, are novel promising therapeutics in the area of bone tissue engineering. Moreover, magnetic nanoparticles, whose integration with other appropriate components is viewed as an intriguing approach to strengthen bone tissue engineering efficacy. We investigated the effect of magnetic enriched with exosomes on osteogenic differentiation.

Materials and Methods

Exosomes were isolated from human adipose-derived mesenchymal stem cells by Exo-spin™ kit (MSC-EX). Alginate (Alg) scaffold containing 1% (w/w) cobalt ferrite nanoparticles (CoFe2O4) was produced. MSC-EX were gently loaded onto Alg and Alg-cobalt ferrite (Alg-CF) scaffolds yielding Alg-EX and Alg-CF-EX scaffolds. The effects of MSC-Ex and magnetic hydrogel composite under an external static magnetic field (SMF) on proliferation and differentiation of MSCs were evaluated by alkaline phosphatase (ALP) activity measurement, alizarin red staining, and energy dispersive X-ray (EDX) analysis.

Results

Our results showed that Alg and Alg-CF scaffolds were not only cytotoxic but also supported AdMSCs proliferation. MSC-EX loading of the scaffolds enhanced AdMSCs proliferation significantly. According to the results, Alg-CF-EX scaffolds under magnetic stimulation exhibited the most potent effect on osteogenic differentiation of cultured AdMSCs as evidenced by higher ALP activity and mineralization.

Conclusion

We provided evidence that the combination of Alg hydrogel, CFNPs, and MSC-EX resulted in the construction of a bone tissue-engineering scaffold that highly supports the osteogenic commitment of MSCs.

The Sensitization of Scintillation in Polymeric Composites Based on Fluorescent Nanocomplexes

The sensitization of scintillation was investigated in crosslinked polymeric composite materials loaded with luminescent gold clusters aggregates acting as sensitizers, and with organic dye rhodamine 6G as the emitting species. The evolution in time of the excited states population in the systems is described by a set of coupled rate equations, in which steady state solution allowed obtainment of an expression of the sensitization efficacy as a function of the characteristic parameters of the employed luminescent systems. The results obtained indicate that the realization of sensitizer/emitter scintillating complexes is the strategy that must be pursued to maximize the sensitization effect in composite materials.

Metal Mimics: Lightweight, Strong, and Tough Nanocomposites and Nanomaterial Assemblies

The ideal structural material would have high strength and stiffness with a tough ductile failure, all with a low density. Historically, no such material exists, and materials engineers have had to sacrifice a desired property during materials selection, with metals (high density), fiber composites (brittle failure), and polymers (low stiffness) having fundamental limitations on at least one front. The ongoing revolution of nanomaterials provides a potential route to build on the potential of fiber-reinforced composites, matching their strength while integrating toughening behaviors akin to metal deformations, all while using low-weight constituents. Here, the challenges, approaches, and recent developments of nanomaterials for structural applications are discussed, with an emphasis on improving toughening mechanisms, which is often the neglected factor in a field that chases strength and stiffness.

The influence of the curing process on the shear thickening performance of RMG and property optimization

A smart composite with both rate-sensitive and magnetic-sensitive properties was prepared by dispersing carbonyl iron powder (CIP) into a silicon–boron copolymer matrix. In addition to following the common preparation procedure, a curing process used in the rubber industry was considered. Several groups of samples were prepared with and without including this curing process. For the samples that underwent the curing process, the absolute shear thickening effect was reduced by less than half compared to the samples that did not undergo the curing process, however, the relative shear thickening effect was increased by up to 6717.50%. In total, 16 groups of samples were tested under different curing conditions, such as different curing times and curing temperatures, to investigate the performance improvement. The results showed that to obtain a better relative shear thickening effect, a curing time of at least 20 min was needed. When the curing temperature was set to 120 °C, the absolute shear thickening effect was maximized. The influences of pyroboric acid and CIPs on the properties of the materials were also studied. Interestingly, the relative magnetorheological effect did not always increase with increasing CIP content. An increase in the amount of pyroboric acid increased the absolute shear thickening effect and decreased the relative shear thickening effect.

The influence of the curing process is studied, and to obtain a better shear thickening performance, the parameter in this curing process is also optimized.

Exploring the Role of Nanoparticles in Enhancing Mechanical Properties of Hydrogel Nanocomposites

Over the past few decades, research studies have established that the mechanical properties of hydrogels can be largely impacted by the addition of nanoparticles. However, the exact mechanisms behind such enhancements are not yet fully understood. To further explore the role of nanoparticles on the enhanced mechanical properties of hydrogel nanocomposites, we used chemically crosslinked polyacrylamide hydrogels incorporating silica nanoparticles as the model system. Rheological measurements indicate that nanoparticle-mediated increases in hydrogel elastic modulus can exceed the maximum modulus that can be obtained through purely chemical crosslinking. Moreover, the data reveal that nanoparticle, monomer, and chemical crosslinker concentrations can all play an important role on the nanoparticle mediated-enhancements in mechanical properties. These results also demonstrate a strong role for pseudo crosslinking facilitated by polymer⁻particle interactions on the observed enhancements in elastic moduli. Taken together, our work delves into the role of nanoparticles on enhancing hydrogel properties, which is vital to the development of hydrogel nanocomposites with a wide range of specific mechanical properties.

Influence of mono-lithium based initiators with different steric volumes on 1,4 unit content of hydroxyl terminated polybutadiene using anionic polymerization

The influence of steric structural factors of mono-lithium based anionic initiators on 1,4 unit content of hydroxyl terminated polybutadiene was investigated.