Search

Self-healing hydrogels have great application potential in the field of bio-sensors due to their self-healing, flexibility and excellent tensile properties. However, most hydrogel-based sensors are processed by template method, which is unable to fabricate complex three-dimensional (3D) structures, and limits the development of hydrogel-based sensor devices. A simple yet efficient one-pot method was proposed to fabricate polyvinyl alcohol/sodium tetraborate/sodium alginate hydrogel inks (SPB), also a fabricating process of self-healing hydrogel based on 3D printing technology has been proposed. The SPB hydrogel rapidly healed (30 s) at room temperature, while its mechanical properties and conductivity also recovered quickly after healing. Besides, it could be used as wearable strain sensors, whose high stretchability (2800 % strain) and sensitivity (gauge factor: 18.56 at 2000 % strain) could not only detect very large stretch deformations, but also detect the tiny pressure changes in the human body, such as finger flexion, knee flexion, and respiration. This study provides a method for the rapid fabrication of complex-structured hydrogel-based sensors, which is helpful for the hydrogel-based sensor applications in human motion detection and wearable devices.

To determine the optimum composition of AS/PVA for bioprinting cartilage scaffold, a molecular simulation combining experimental method was employed to investigate the microstructure, physicochemical properties and printability of AS/PVA blending hydrogels at different compositions. The compatibility analysis results show that SA and PVA have a good compatibility, they are miscible at any compositions. Mechanical properties analysis indicates that the tensile strength of 8SA/2PVA is the best, and compared with 8SA/2PVA, 7SA/3PVA possesses a better toughness and similar tensile strength. Moreover, FFV value and pore size decrease with the increase of PVA content, indicating the incorporation of PVA makes the system denser and pore size smaller, and the hydrogel of 8SA/2PVA possesses the optimal pore structure for the proliferation of chondrocytes. The main reason behind the conclusions obtained above is attributed to the strong hydrogen bond and intermolecular interaction between SA and PVA molecular chains. Finally, the results of printability indicates that, due to the fluidity of PVA, the forming quality becomes worse with the increase of PVA content, and when the PVA content in hydrogel precursors is within 30 wt.%, the forming quality is relatively good. Comprehensive considering the results above, the blend hydrogel of 8SA/2PVA was selected out and considered to be the most suitable for 3D printing cartilage scaffolds.

Absract Polylactic acid (PLA), due to its high mechanical strength, biocompatibility, excellent biodegradability and good processing characteristics, can be used to print the bone scaffold with complex structures, but the poor cell affinity and inflammation resulted by the acidity of intermediate produce still pose a challenge. To address these issues, o-carboxymethyl chitosan (CMC) was used to modify PLA, and the phase miscibility of PLA/CMC blends with different component ratios was investigated by a multi-scale method. Here, molecular simulation and experimental methods were applied to predict the miscibility of polylactic acid and o-carboxymethyl chitosan blends. Results indicated that PLA and CMC are miscible when the concentration of CMC in blends below 20 wt%, and partially miscible at 30 wt% concentration of CMC, but completely immiscible at higher CMC content (>30 wt%). Conclusions from this work can be used to forecast the miscibility of PLA/CMC composites at different compositions and can provide a scientific basis for formula designs of PLA/CMC polymer composites for 3D printing artificial bone scaffolds.

Hydrazine hydrate oxidation assisted water splitting can effectively reduce the energy consumption of conventional water electrolysis due to the lower thermodynamic anode potential, which stimulates the development of highly efficient bifunctional electrocatalysts. Herein, we report a solvothermal synthesis strategy to prepare Rh nanocubes (NCs) with specific exposed Rh (1 0 0) planes. Benefiting from higher coordination unsaturation and reactivity of the Rh (1 0 0) plane, Rh NCs exhibit higher catalytic performance than commercial Rh black toward hydrazine hydrate oxidation reaction (HHOR) and hydrogen evolution reaction (HER). To achieve the current density of 10 mA cm−2 in HHOR and HER, the anode and cathode potentials required for Rh NCs (240 and –32 mV) are better than those of commercial Rh black (291 and −43 mV). Thus, Rh NCs are used as bifunctional electrocatalysts to drive a HHOR assisted water splitting cell, which can achieve long-term stable electrochemical hydrogen production at a voltage of ∼ 0.223 V, demonstrating a promising energy-saving hydrogen production strategy.

The nano-silica can be incorporated into polymers for improved mechanical properties. Notably, the interaction between nano-silica and polymer is of a microscopic phenomenon and thus, hard to observe and study by using experimental methods. Based on molecular dynamics, this paper presents a study on the properties and the interaction mechanism of nano-silica in the polyvinyl alcohol (PVA)/polyacrylamide (PAM) blends at an atomic level. Specifically, six blends of PVA/PAM with varying concentrations of nano-silica (0-13wt%) and two interfacial interaction models of polymers on the silica surface were designed and analyzed at an atomic level in terms of concentration profile, mechanical properties, fractional free volume (FFV), dynamic properties of polymers and X-ray diffraction patterns. The concentration profile results and micromorphologies of equilibrium models suggest PAM molecular chains are easier to be adsorbed on the silica surface than PVA molecular chains in blends. The incorporation of nano-silica into the PVA/PAM blends can increase the blend mechanical properties, densities, and semicrystalline character. Meanwhile, the FFV and the mobility of polymer chain decrease with the silica concentration, which agrees with the results of mechanical properties, densities, and semicrystalline character. Our results also illustrate that an analysis of binding energies and pair correlation functions (PCF) allows for the discovery of the interaction mechanism of nano-silica in PVA/PAM blends; and that hydrogen bond interactions between polar functional groups of polymer molecular chains and the hydroxyl groups of the silica surface are involved in adsorption of the polymers on the silica surface, thus affecting the interaction mechanism of nano-silica in PVA/PAM blend systems.

Binder properties are a key factor affecting the quality of bone scaffolds produced using 3D powder printing. In this research, molecular dynamics simulation (MD) and experimental methods were applied to study the cohesive energy density, mechanical properties, bonding behavior, and surface morphology of three polymer binders (PVP, PAM, PVA) employed in the 3D fabrication of hydroxyapatite (HA) bone scaffolds. The bonding mechanisms of the three polymer binders were revealed by analyzing the interaction between the binders and the HA surface. The binding energies between the binders and HA are associated with the cohesive energy density and viscosity of each of the binders, which are attributed to functional groups in the binders. The mechanical properties determined experimentally for the bone scaffolds produced using each of the three polymer binders were in a different relative order than the engineering modulus of the binders and the interaction between the binders and HA calculated in simulations. This is a reflection of the mechanical properties of bone scaffolds being a comprehensive reflection of the basic materials and their bonding effect. Finally, SEM imaging indicated additional factors affecting the mechanical properties and degradation rate of the scaffolds. Conclusions from this work can be used to forecast the properties of three commonly used polymer binders and provide a theoretical basis for the choice of binders in the production of 3DP-fabricated bone scaffolds.

The objectives of this study were to develop a computational model based on molecular dynamics technique to investigate the compatibility and mechanical properties of Polyacrylamide (PAM)/Polyvinyl alcohol (PVA) blends. Five simulation models of PAM/PVA with different composition ratios (4/0, 3/1, 2/2, 1/3, 0/4) were constructed and simulated by using molecular dynamics (MD) simulation. The interaction mechanisms of molecular chains in PAM/PVA blend system were elaborated from the aspects of the compatibility, mechanical properties, binding energy and pair correlation function, respectively. The computed values of solubility parameters for PAM and PVA indicate PAM has a good miscibility with PVA. The results of the static mechanical analysis, based on the equilibrium structures of blends with differing component ratios, shows us that the elastic coefficient, engineering modulus, and ductility are increased with the addition of PVA content, which is 4/0 PAM/PVA3/1 PAM/PVA2/2 PAM/PVA1/3 PAM/PVA0/4 PAM/PVA. Moreover, binding energy results indicate that a stronger interaction exists among PVA molecular chains comparing with PAM molecular chains, which is why the mechanical properties of blend system increasing with the addition of PVA content. Finally, the results of pair correlation functions (PCFs) between polar functional groups and its surrounding hydrogen atoms, indicated they interact with each other mainly by hydrogen bonds, and the strength of three types of polar functional groups has the order of O(-OH)O(-C=O)N(-NH

To investigate the effects of composition ratios on the properties of PVA/PVP blend membrane, five models of blend membrane with the composition ratios of 4/0, 3/1, 2/2, 1/3, and 0/4 were constructed and simulated using the molecular dynamics simulation. The solubility parameters, mechanical properties, binding energy, pair correlation function, free volume and diffusion of H2O molecules were studied, respectively. Results show that PVA has a good compatibility with PVP, the engineering modulus and binding energy decrease with the addition of PVP content. The diffusion of H2O molecule and fractional free volume increase with the addition of PVP content, the bigger the fractional free volume, the better the diffusion ability for H2O molecules in system. Additionally, the pair correlation functions indicate that the hydrogen bonds are more likely to be formed between H2O molecules and polar functional groups, with the increase of PVP content. This is due to the polarity effect of amide groups (NCO) in PVP is stronger than that of hydroxyl groups (OH) in PVA. A stronger polarity effect can make the hydrogen bonds more easily to be formed between polar groups and water molecules, and this is why the hydrophilicity of membrane increases with the addition of PVP. Keywords: Blend membrane, Molecular dynamics, Compatibility, Mechanical properties, Diffusion, Hydrophilicity

In this paper, a magnetic nanoporous carbon (Fe3O4/NPC) was successfully synthesized by using MOF-5 as carbon precursor and Fe salt as magnetic precursor. The texture properties of the as-synthesized nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), vibration sample magnetometer (VSM), and N2 adsorption–desorption isotherms. The Fe3O4/NPC had a high surface area with strong magnetic strength. Its adsorption behavior was tested by its adsorption capacity for the removal of methylene blue from aqueous solution. The results demonstrated that the Fe3O4/NPC had a high adsorption capacity, rapid adsorption rate, and easy magnetic separabilty. Moreover, the adsorbent could be easily regenerated by washing it with ethanol. The Fe3O4/NPC can be used as a good alternative for the effective removal of organic dyes from wastewater.

The aim of this paper is to investigate the deformation and springback behavior of 3D tubes under complex stress conditions. We proposed a new semi-analytical method to predict the springback behavior of 3D tubes. In the new method, discretization and approximation are implemented on the tube axis so that the deformation parameters (bending radiuses and twisting angles) can be derived. Based on the discretization and approximation, a theoretical model is proposed to calculate the stress distributions and residual deformations. The new method is applied on a typical 3D tube for springback prediction, and comparison between theoretical and experimental results shows a remarkable agreement. Additionally, it is also found that the radii after springback will decrease inversely with the increase of twisting angle, and this tendency will become clearer when the bending radius increases.

An efficient synergistic catalyst, AgPd bimetal supported on metal–organic framework derived porous carbon (AgPd/MOF-5-C), was fabricated for the first time. The catalyst exhibited 100% H2 selectivity and high catalytic activity in hydrogen generation from formic acid at ambient conditions. The initial turnover frequency could reach as high as 854 h− 1. The combination of distinct interaction among bimetal, support and high dispersion of nanoparticles drastically enhances the catalytic performance of the resulted catalyst.

To investigate the effect of composition ratio on the properties for PVA/PAA blend membrane, five simulation models of PVA/PAA with different composition ratios (4/0, 3/1, 2/2, 1/3, 0/4) were constructed and simulated by using molecular dynamics (MD) simulation. The effects of composition ratio on the properties for blends were elaborated from the aspects of the compatibility, mechanical properties, binding energy, pair correlation function, and diffusion of water molecules, respectively. The result of solubility parameter indicated PVA has a good miscibility with PAA, and the static mechanics analysis shows the mechanical properties and ductility are decreased with the increase of PAA content in the blend systems. Moreover, the analysis of binding energy and pair correlation function reveal the reason why the mechanical properties of systems decrease with the additional of PAA. Additionally, the analytical results of fractional free volume is inconsistent with the diffusion ability of H2O molecules, and the diffusion ability of H2O molecules in blend systems has the order of 4PPVA/0PAA > 3PVA/1PAA > 2PVA/2PAA > 1PVA/3PAA > 0PVA/4PAA. The main reason for this phenomenon is that the polarity effect of carboxylic acid groups (−COOH) in PAA is stronger than that of hydroxyl groups (−OH) in PVA. Keywords: PVA/PAA blend membrane, Molecular dynamics, Compatibility, Binding energy, Mechanical properties, Diffusion

The carbon-supported Pd–Au catalysts (Pd–Au/C) with different alloying degree are prepared in the aqueous solution with and without tetrahydrofuran (THF) by a chemical reduction method. The studies of X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) measurements show that the alloying degree of the Pd–Au/C catalyst prepared in the aqueous solution is much lower than that of Pd–Au/C catalyst prepared in the H 2 O/tetrahydrofuran (THF) mixture solution, indicating the presence of THF can obviously enhance the alloying degree of Pd–Au nanoparticles during the preparation of Pd–Au/C catalyst. The electrochemical measurements illustrate the electrocatalytic activity of Pd–Au/C catalyst for the formic acid electrooxidation is strongly dependent on alloying degree of Pd–Au nanoparticles. The Pd–Au/C catalyst with high alloying degree shows a higher electrocatalytic activity and stability for the formic acid electrooxidation compared to the Pd–Au/C catalyst with low alloying degree, which can be ascribed to enhancement of CO tolerance and possible suppression of dehydration pathway in the course of formic acid electrooxidation.

The organic sol method for preparing ultrafine transition metal colloid particles reported for the first time by Bonnemann et al. [H. Bonnemann, W Brijoux, R. Brinkmann, E. Dinjus, T. Jou beta en, B. Korall, Angew. Chem. Int. Ed. Engl., 30 (1991) 1312] has been improved in this paper. The improved organic sol method uses SnCl2 as the reductant and methanol as the organic solvent. Thus, this method is very simple and inexpensive. It was found that the average size of the Pt particles in the Pt/C catalysts can be controlled by adjusting the evaporating temperature of the solvent. Therefore, the Pt/C catalysts prepared by the same method are suitable for evaluating the size effect of the Pt particles on electrocatalytic performance for methanol oxidation. The results of the X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed that when the evaporating temperatures of the solvent are 65, 60, 50, 40, and 30 degrees C, the average sizes of the Pt particles in the Pt/C catalysts prepared are: 2.2, 3.2, 3.8, 4.3, and 4.8 nm, respectively. The X-ray photoelectron spectroscopic (XPS) results demonstrated that the small Pt particles are easily oxidized and the decomposition/adsorption of methanol cannot proceed on the surfaces of Pt oxides.