Mechanical Compatibility Research Articles

Crack path on the railway tank of Viareggio disaster

We describe the process of forming the gash in the tank of the first wagon of the freight car n. 50,325 during the accident that caused the known Viareggio disaster in 2009. Analyzing the findings of the accident and details of the fracture surfaces on the tank, as well as the deforming state, both of the tank around the hole and the element of the infrastructure that caused the hole, the cause-effect relationship between the traces left by the impact on the two structures involved is identified throughout the hole extension. In addition, we verify the geometric, morphological, physical and mechanical compatibility between some traces of the impact of the same tank with other elements of the infrastructure, to remark the extraneity of these with the formation of the gash in the tank.

Evaluation of a simple off-the-shelf bi-layered vascular scaffold based on poly(L-lactide-co-ε-caprolactone)/silk fibroin in vitro and in vivo.

Purpose: In the field of small-caliber vascular scaffold research, excellent vascular remodeling is the key to ensuring anticoagulant function. We prepared an off-the-shelf bi-layered vascular scaffold with a dense inner layer and a loose outer layer and evaluated its remodeling capabilities by in vivo transplantation.Materials and Methods: Based on poly(L-lactide-co-ε-caprolactone) (PLCL), silk fibroin(SF), and heparin (Hep), PLCL/SF/Hep bi-layered scaffolds and PLCL/Hep bi-layered scaffolds were prepared by electrospinning. The inner layer was a PLCL/SF/Hep or PLCL/Hep nanofiber membrane, and the outer layer was PLCL/SF nano yarn. The in vitro tests included a hydrophilicity test, mechanical properties test, and blood and cell compatibility evaluation. The in vivo evaluation was conducted via single rabbit carotid artery replacement and subsequent examinations, including ultrasound imaging, immunoglobulin assays, and tissue section staining.Results: Compared to the PLCL/Hep nanofiber membrane, the hydrophilicity of the PLCL/SF/Hep nanofiber membrane was significantly improved. The mechanical strength met application requirements. Both the blood and cell compatibility were optimal. Most importantly, the PLCL/SF/Hep scaffolds maintained lumen patency for 3 months after carotid artery transplantation in live rabbits. At the same time, CD31 and α-SMA immunofluorescence staining confirmed bionic endothelial and smooth muscle layers remodeling.Conclusion: Using this hybrid strategy, PLCL and SF were combined to manufacture bi-layered small-caliber vascular scaffolds; these PLCL/SF/Hep scaffolds showed satisfactory vascular remodeling.

400 °C Sensor Based on Ni/4H-SiC Schottky Diode for Reliable Temperature Monitoring in Industrial Environments.

This paper presents a high-temperature probe suitable for operating in harsh industrial applications as a reliable alternative to low-lifespan conventional solutions, such as thermocouples. The temperature sensing element is a Schottky diode fabricated on 4H-SiC wafers, with Ni as the Schottky metal, which allows operation at temperatures up to 400 °C, with sensitivities over 2 mV/°C and excellent linearity (R2 > 99.99%). The temperature probe also includes dedicated circuitry for signal acquisition and conversion to the 4 mA–20 mA industrial standard output signal. This read-out circuit can be calibrated for linear response over a tunable temperature detection range. The entire system is designed for full electrical and mechanical compatibility with existing conventional probe casings, allowing for seamless implementation in a factory’s sensor network. Such sensors are tested alongside standard thermocouples, with matching temperature monitoring results, over several months, in real working conditions (a cement factory), up to 400 °C.

Mechanical derivation of elastic constants of ε-martensite

This work presents direct formulas to compute the HCP elastic constants of ε-martensite from the FCC ones of austenite. The derivation is performed thanks to mechanical compatibility arguments while considering ε-martensite as a laminate structure of twinned and untwinned FCC phases. The formulas are applied to predict the elastic constants of several alloys and very good agreement with measurements is found. According to these relations, directional Young moduli of ε-martensite are most of the time stiffer than the austenite ones and the (0001) shear modulus is always greater than the (111) one, which hardens dislocation glide parallel to the interfaces.

Evaluation of the mechanical compatibility of additively manufactured porous Ti–25Ta alloy for load-bearing implant applications

Integrating porous networks in load-bearing implants is essential in order to improve mechanical compatibility with the host tissue. Additive manufacturing has enabled the optimisation of the mechanical properties of metallic biomaterials, notably with the use of novel periodic regular geometries as porous structures. In this work, we successfully produced solid and lattice structures made of Ti–25Ta alloy with selective laser melting (SLM) using a Schwartz primitive unit-cell for the first time. The manufacturability and repeatability of the process was assessed through macrostructural and microstructural observations along with compressive testing. The mechanical properties are found to be suitable for bone replacement applications, showing significantly reduced elastic moduli, ranging from 14 to 36 GPa depending on the level of porosity. Compared to the conventionally used biomedical Ti–6Al–4V alloy, the Ti–Ta alloy offers superior mechanical compatibility for the targeted applications with lower elastic modulus, similar strength and higher ductility, making the Ti–25Ta alloy a promising candidate for a new generation of load-bearing implants.

Mechanical properties and cell compatibility of a chitosan-graphene oxide guided bone regeneration composite membrane

Objective: To explore the feasibility of graphene oxide (GO)-chitosan (CS) guided bone regeneration composite membrane being used as a new guided bone regeneration (GBR) membrane by testing its tensile strength and its effect on the proliferation of human gingival fibroblasts (HGF). Methods: The CS solution and GO solution were mixed in following ratios, ultrasonically crushed and dispersed, and formed into membranes by self-evaporation. Composite membrane with 0.5%, 1.0%, 2.0%, 4.0%, 6.0%, 8.0% GO in CS was prepared. The tensile strength of the composite membranes was tested by mechanical universal testing machine (n=6). The microstructure of the composite membrane with the best tensile strength was observed by scanning electron microscopy and transmission electron microscopy. X-ray diffraction was used to characterize the ingredients of the material. A group of samples was prepared again with the proportion of the highest tensile strength composite membrane, and were immersed in a sodium hydroxide solution for acid removal. The tensile strength of the new group of samples was tested. The newly extracted impacted teeth were collected from the Department of Oral and Maxillofacial Surgery, Stomatologic Hospital and College, Anhui Medical University, and the gingival tissues remained on the teeth were taken for primary HGF and were cultured to P2 generation, which were identified by immunocytochemical staining methods. Cell counting kit-8 (CCK-8) was applied to detect cell counts in the blank control group, the pure CS membrane group, and the composite membrane group with the highest tensile strength (n=5) and all groups co-cultured with the HGF for 24 h and 48 h. Results: After adding GO, the cross-section of the composite membrane was in an ordered layer structure. X-ray diffraction analysis showed that GO could be found in the composite membrane. The tensile strength increased with the increase of GO ratio. When the mass fraction of GO in CS was 4.0%, the tensile strength reached (134.8±7.3) MPa and the tensile strength reached (144.6±8.1) MPa after deacidification of the composite membrane. The CCK-8 test of HGF showed that there was no significant difference in absorbance between the pure CS membrane group and the GO/CS composite membrane group when they were compared with the blank control group (P>0.05). Conclusions: When the mass fraction of GO in CS is 4.0%, the composite membrane has the best tensile strength. The composite membrane showes good cytocompatibility, which lays a foundation for further in vivo experiments and the development of a new generation of GBR membrane.

Mechanical compatibility and adhesion between alkali-activated repair mortars and Portland cement concrete substrate

Abstract Alkali-activated materials (AAM) have been widely promoted as potential repair material for Portland-cement concrete (PCC). However, a thorough evaluation of compatibility and adhesion of AAM to PCC substrates and the correlation of these properties to the AAM composition is still required. AAMs obtained from metakaolin (MK) partially substituted (0, 20, 40, 60 and 80 wt%) with blast furnace slag (BFS) and their mechanical compatibility with a representative PCC substrate was investigated. Mortars with equivalent compressive strength and modulus of elasticity (with and without polypropylene fiber reinforcement) were applied onto the substrate and subjected to bond tests (pull-off and bending tests). Results indicate that neat MK-based mortars present excellent adhesion to PCC, but are vulnerable to delamination. The addition of 20% BFS mitigates this issue, by reducing the solution demand and drying shrinkage. Higher contents of BFS (>60%) have reduced bond strength, probably due to high alkalinity.

Processing and properties of a new biodegradable Mg−Zn−Ca−Zr alloy

AbstractMagnesium alloys are used for degradable orthopaedic and cardiovascular implants due to their favourable mechanical and biological properties, degradation ability in physiological environment and stimulatory effect on the new bone formation. The research challenges are related to the increase of biological and mechanical compatibility. For the present study, a magnesium based alloy design was conducted to the following chemical composition: Mg−2.7Zn−1Ca−0.6Zr (wt.%). A complex thermomechanical processing route was applied: a plastic deformation by extrusion at various temperatures and deformation degrees (400 °C–480 °C, ϵ = 20 %–40 %), followed by various final heat treatments at 200 °C–400 °C for 10 min–60 min. Further, the influence of processing parameters upon the structure, mechanical properties and biological response was studied. Processed specimens were characterized by scanning electron microscopy (secondary electron imaging and energy dispersive spectroscopy) and mechanically by tensile tests. The most representative results were obtained for the samples extruded at 450 °C/ϵ = 20 %, followed by a final heat treatment at 350 °C/15 min, air cooling. Further, for samples which revealed promising results, in‐vitro testing was developed. Biocompatibility testing of the Mg−2.7Zn−1Ca−0.6Zr (wt.%) alloy was realized by indirect contact studies using the Vero (ATCC® CCL‐81™, American Type Culture Collection) cell line. Cells morphologies, cell viability and proliferation were evaluated.

Facile Fabrication of Microspheres and Microcapsules from a Recombinant Spider Eggcase Silk Protein for Drug Delivery

Spider silk is renowned for its exceptional mechanical properties, and compatibility and biodegradability for various functional applications, such as drug delivery. By a facile HFIP (1,1,1,3,3,3-hexafluoro-2-propanol)-on-Oil method, microspheres and microcapsules were assembled from a recombinant spider eggcase silk protein. Doxorubicin (Dox) can be loaded into microspheres or microcapsules before or after their preparation, while maintaining morphological integrity. The isoelectric point of the silk proteins was 4.8, which affected the drug loading of silk spheres for different pH media. For enzyme-assisted drug delivery, Dox-loaded silk spheres effectively released the drug under enzymatic degradation by addition of proteinase K.

Stable cross-linked gel terpolymer electrolyte containing methyl phosphonate for sodium ion batteries

The novel bifunctional methyl phosphonate which combines the good polymerization ability of acrylate, the adjustable flexibility of ethylenedioxy group and the flame retardant properties of phosphonate is designed and synthesized. The corresponding ternary gel polymer electrolyte is prepared by radical cross-linking copolymerization. The gel terpolymer electrolyte has good thermal stability with the onset decomposition temperature of 250 °C, excellent electrochemical stability of up to 5.0 V (vs. Na+/Na) and high ionic conductivity of 5.13 mS cm−1. Moreover, the gel polymer electrolyte can enhance interfacial adhesion between the membrane and the electrodes. The Na3V2(PO4)3/Na cell using phosphorus containing gel terpolymer electrolyte shows ultra-long cycling performance and better cycle stability and rate performance than the corresponding conventional liquid electrolyte, phosphorus containing gel bipolymer electrolyte and other crosslinker based cells. Meanwhile, the glass fiber separator filled with gel polymer electrolyte maintains better integrity than liquid electrolyte after 1000 cycles, which means the gel polymer electrolyte has good mechanical property and compatibility. The gel polymer electrolyte based sodium-ion battery also exhibits superior cycle stability compared to the battery with liquid electrolyte when running at high temperature of 60 °C. The strong interaction between methyl phosphonate and sodium ion is studied by FT-IR, 31P NMR and HRMS, and demonstrated by theoretical calculation.

Vulcanization and Thermal Properties of Silicone Rubber/Fluorine Rubber Blends

With the rapid development of automobile, aviation, aerospace, machinery and other fields, rubber products used in these fields required to meet higher requirements. Fluorine rubber (FKM) and silicone rubber (MVQ) have excellent performance in some areas. However, the FKM is poor in low-temperature resistance and processing performance, limiting its applicability. Although the MVQ has a wide range of temperature and excellent processing performance, but its mechanical properties and oil resistance are not good. In this work, the MVQ/FKM blends were prepared by two different mechanical blending methods. The effects of the mixing process, mass ratio, curing system and conditions of the blends were studied. The chemical compositions of the blends were analyzed by infrared spectroscopy (IR). The compatibility and the thermal properties of the blends were investigated by dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), respectively. The results showed that the mechanical properties, compatibility and thermal stability of the blends were the best when they were prepared by kneading the FKM and MVQ individually in a two-rool mill roll, then mixing them together homegeneously with an MVQ/FKM mass ratio of 10/90, curing system of (4 phr, 1/9) dicumyl peroxide (DCP)/N, N-Dicinnamylidene-1, 6-hexanediamine (3# Vulcanizer), first curing conditions at 170 °C under 10 MPa for 30 min and post curing conditions at 200 °C for 6 hours at 1 atmospheric pressure.

Binary Modification of Eucommia ulmoides Gum Toward Elastomer with Tunable Mechanical Properties and Good Compatibility

ABSTRACTEucommia ulmoides gum (EUG) was applied in blend rubber with a heavily limited amount because of its duality of rubber and plastic, and an efficient way of triazolinedione (TAD)‐based Alder‐ene reaction was used to improve the elastic properties of EUG. Binary modification of EUG with two TADs containing hexyl and polyhedral oligomeric silsesquioxane (POSS) groups were conducted to generate the modified EUG elastomers with tunable mechanical properties and good compatibility by varying TAD contents. When the low hexyl (1%) and POSS (0.2%) TADs incorporated, the modified EUGs displayed high tensile strength of 36.57 MPa with the elongation at break of 876%, and thus high toughness of 152.14 MJ m−3. If high contents of hexyl (20%) and POSS (0.2%) TADs employed, the modified EUGs exhibited excellent elongation at break of 1165% and recovery rate of 60%, and especially its loss factor reached up to 0.83‑0.65 at 20‑70°C. Therefore, the modified EUGs containing the polar urazole and POSS groups should be a novel elastomer with good compatibility, wear resistance, and damping properties. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019

Collagen type I and hyaluronic acid based hybrid scaffolds for heart valve tissue engineering.

Tissue engineers have achieved limited success so far in designing an ideal scaffold for aortic valve; scaffolds lack in mechanical compatibility, appropriate degradation rate, and microstructural similarity. This paper, therefore, has demonstrated a carbodiimide-based sequential crosslinking technique to prepare aortic valve extracellular matrix mimicking (ECM) hybrid scaffolds from collagen type I and hyaluronic acid (HA), the building blocks of heart valve ECM, with tailorable crosslinking densities. Swelling studies revealed that crosslinking densities of parent networks increased with increasing the concentration of the crosslinking agents whereas crosslinking densities of hybrid scaffolds averaged from those of parent collagen and HA networks. Hybrid scaffolds also offered a wide range of pore size (66-126 μm) which fulfilled the criteria for valvular tissue regeneration. Scanning electron microscopy and images of Alcian blue-Periodic acid Schiff stained samples suggested that our crosslinking technique yielded an ECM mimicking microstructure with interlaced bands of collagen and HA in the hybrid scaffolds. The mutually reinforcing networks of collagen and HA also resulted in increased bending moduli up to 1660 kPa which spanned the range of natural aortic valves. Cardio sphere-derived cells (CDCs) from rat hearts showed that crosslinking density affected the available cell attachment sites on the surface of the scaffold. Increased bending moduli of CDCs seeded scaffolds up to two folds (2-6 kPa) as compared to the non-seeded scaffolds (1 kPa) suggested that an increase in crosslinking density of the scaffolds could not only increase the in vitro bending modulus but also prevented its disintegration in the cell culture medium.

Influence of an Impregnation Treatment on the Morphology and Mechanical Behaviour of Flax Yarns Embedded in Hydraulic Lime Mortar

The increasing attention toward environmental aspects has led, also in the sector of construction materials, to the need for developing more eco-friendly solutions. Among several options, the employment of low energy raw materials appears as an efficient solution intended to enhance the sustainability of building structures. One of the applications moving in this direction is the use of plant fibers as a reinforcement in cement-based composites, hence named as natural textile reinforced mortar (NTRM) composites. Although representing a promising technique, there are still several open issues concerning the variability of plant fibers properties, the durability, and the mechanical compatibility with the mortar. This study aims at investigating the influence of an impregnation process on the thread’s morphology and on the mechanical response. Therefore, the geometry of dry and impregnated flax threads is identified by using scanning electron microscope (SEM) images analysis, and their mechanical response in tension is assessed. In addition, the fibers-to-mortar bond behavior is investigated by means of pull-out tests. The proposed results show that the impregnation procedure employed, although not improving the fibers-to matrix bond, leads to a standardisation of the threads morphology and reduces the thread’s deformability in tension, and paves the way for further investigations on a larger scale.

Hot Glue Gun Releasing Biocompatible Tissue Adhesive

AbstractTissue bioadhesives are widely used in dermatology, surgery rooms, and in the field. Despite their advantages over sutures and staples, currently available tissue glues are limited by their mechanical properties and toxicity. Here, a new approach is described for wound closure that is based on a biocompatible, low melting point four‐armed N‐hydroxy succinimide‐modified polycaprolactone (star‐PCL‐NHS). Star‐PCL‐NHS is inserted into a hot melt glue gun, melts upon minimal pressure, and is extruded directly onto the wound, where it solidifies, bonding strongly with both edges of the wound. Changes in molecular weight allow control of adhesive strength, melting point, and elasticity properties. In vitro and in vivo evaluations confirm the biocompatibility of this system. The straightforward synthetic scheme and the simple delivery method, combined with the desirable mechanical properties, tunability, and tissue compatibility, are desirable traits in wound management.

Wearable Fiber-Based Organic Electrochemical Transistors as a Platform for Highly Sensitive Dopamine Monitoring.

Fiber-based organic electrochemical transistors (FECTs) provide a new platform for the realization of an ultrafast and ultrasensitive biosensor, especially for the wearable dopamine (DA)-monitoring device. Here, we presented a fully filament-integrated fabric, it exhibited remarkable mechanical compatibility with the human body, and the minimum sensing unit was an organic electrochemical transistor (OECT) based on PVA- co-PE nanofibers (NFs) and polypyrrole (PPy) nanofiber network. The introduction of NFs notably increased the specific surface area and hydrophilicity of the PA6 filament, resulting in the formation of a large area of intertwined PPy nanofiber network. The electrical performance of PPy nanofiber network-modified fibers improved considerably. For the common FECTs, the typical on/off ratio was up to two orders of magnitude, and the temporal recovery time between on and off states was shortened to 0.34 s. Meanwhile, the device exhibited continuous cycling stability. In addition, the performances of FECT-based dopamine sensors depending on different gate electrodes have also been investigated. The PPy/NFs/PA6 filament-based dopamine sensor was more superior to the gold and platinum (Pt) wires, and the sensor presented long-term sensitivity with a detection region from 1 nM to 1 μM, rapid response time to a set of DA concentrations, remarkable selectivity in the presence of sodium chloride, uric acid, ascorbic acid and glucose, and superior reproducibility. Moreover, it could also be woven into the fabric product. The novel and wearable FECT device shows the potential to become the state-of-the-art DA-monitoring platform.

Flexible, Conformal Organic Synaptic Transistors on Elastomer for Biomedical Applications

AbstractBioelectronics in synaptic transistors for future biomedical applications, such as implanted treatments and human–machine interfaces, must be flexible with good mechanical compatibility with biological tissues. The rigid nature and high deposition temperature in conventional inorganic synaptic transistors restrict the development of flexible, conformal synaptic devices. Here, the dinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]‐thiophene organic synaptic transistor on elastic polydimethylsiloxane is demonstrated to avoid these limitations. The unique advantages of organic materials in low Young's modulus and low temperature process enable seamless adherence of organic synaptic transistors on arbitrary‐shaped objects. On 3D curved surfaces, the essential synaptic functions, such as potentiation/depression, short/long‐term synaptic plasticity, and spike voltage–dependent plasticity, are successfully realized. The time‐dependent surface potential characterization reveals the slow polarization of dipoles in the dielectric is responsible for hysteresis and synaptic behaviors. This work represents that organic materials offer a potential platform to realize the flexible, conformal synaptic transistors for the development of wearable and implantable artificial neuromorphic systems.

Collagen-based bioinks for hard tissue engineering applications: a comprehensive review.

In the last few years, additive manufacturing (AM) has been gaining great interest in the fabrication of complex structures for soft-to-hard tissues regeneration, with tailored porosity, and boosted structural, mechanical, and biological properties. 3D printing is one of the most known AM techniques in the field of biofabrication of tissues and organs. This technique opened up opportunities over the conventional ones, with the capability of creating replicable, customized, and functional structures that can ultimately promote effectively different tissues regeneration. The uppermost component of 3D printing is the bioink, i.e. a mixture of biomaterials that can also been laden with different cell types, and bioactive molecules. Important factors of the fabrication process include printing fidelity, stability, time, shear-thinning properties, mechanical strength and elasticity, as well as cell encapsulation and cell-compatible conditions. Collagen-based materials have been recognized as a promising choice to accomplish an ideal mimetic bioink for regeneration of several tissues with high cell-activating properties. This review presents the state-of-art of the current achievements on 3D printing using collagen-based materials for hard tissue engineering, particularly on the development of scaffolds for bone and cartilage repair/regeneration. The ultimate aim is to shed light on the requirements to successfully print collagen-based inks and the most relevant properties exhibited by the so fabricated scaffolds. In this regard, the adequate bioprinting parameters are addressed, as well as the main materials properties, namely physicochemical and mechanical properties, cell compatibility and commercial availability, covering hydrogels, microcarriers and decellularized matrix components. Furthermore, the fabrication of these bioinks with and without cells used in inkjet printing, laser-assisted printing, and direct in writing technologies are also overviewed. Finally, some future perspectives of novel bioinks are given.

Photoactive Organic Substrates for Cell Stimulation: Progress and Perspectives

AbstractModulating the cell membrane potential provides an opportunity to control electrical signaling that is central to cellular physiology and its proper biological function. Among the many technological tools available to enable this modulation, optical stimulation through a photoactive substrate is a powerful strategy that is minimally invasive and wireless. This is critical to avoid disrupting the structural integrity of the cell membrane that is often caused by the use of electrical stimulation electrodes or changing its genetic footprints if optogenetics is the approach taken to photomodulate its electrophysiology. The use of a photoactive substrate such as an organic semiconductor combines optoelectronic properties with mechanical tissue compatibility, which is unachievable with inorganic semiconductors. This research news first discusses the mechanisms of cell photostimulation via these organic photoactive substrates and techniques employed to characterize their photoresponse. Then a summary of the relevant organic materials and their recent applications in cellular photostimulation is presented. Finally, the challenges in the field are described and a perspective on how to address these is provided.

Recommendation of RILEM TC 243-SGM: functional requirements for surface repair mortars for historic buildings

Surface repair mortars are used for the compensation, or repair, of lost portions of surface materials in historic masonry buildings. It is recommended that their design and application should be performed in a wider context of conservation values related decision making, to prioritise preservation of original fabric, authenticity of approach and maintenance of integrity, and not just on technical principles alone. However, a technical context for their design does exist, that requires understanding of the properties of the substrate that they will be applied onto, and adherence to minimum aesthetic (colour and texture) requirements. The principles of physical, mechanical and chemical compatibility of repair apply and the attributes of the repair mortar should be carefully matched to the substrate alongside a sacrificial behaviour (not more durable than the material being replaced). Guidance is given on the design, application and the functional requirements that must be met when using surface repair mortars. © 2019, RILEM.