Tubular Geometry Research Articles

Continuum modeling of nonlinear buckling behavior of CNT using variational asymptotic method and nonlinear FEA

Carbon nanotubes (CNTs) exhibit a unique buckling behavior due to their slender tubular geometry and thin-walled circular cross section. This study aims to analyze effect of nonlinear cross-sectional deformation on buckling of CNTs. To accomplish this, CNTs are modeled as beam structures, and the analysis is conducted using the Variational Asymptotic Method (VAM) and a geometrically exact beam theory, as well as nonlinear finite element analysis (FEA). The study considers various loading cases, including pure axial compression and combined loading scenarios, such as bending-axial compression and torsion-axial compression. The results of the study indicate that inclusion of cross-sectional deformation-induced nonlinearity reduces the critical buckling load of CNTs. The reduction is 2–5% for pure axial compression and 10–40% for combined loading cases. The results are validated against existing literature and commercial finite element software, ABAQUS®. Additionally, parametric studies with different slenderness and radius-to-thickness ratios were carried out to further understand the impact of these parameters on buckling of CNTs. Finally, the study presents 3D deformed shapes of CNTs during buckling by combining the results of the 1D analysis and the 2D cross section analysis. The findings show that nonlinearity associated with radius-to-thickness ratio has a significant impact on the cross-sectional ovalisation of CNTs and is critical in evaluating their buckling behavior. This aspect of nonlinearity is often overlooked in continuum modeling methods of CNTs, making this study an important contribution to the field.

Fast One-Step Fabrication of Highly Regular Microscrolls with Controllable Surface Morphology.

Although rolling origami technology has provided convenient access to three-dimensional (3D) microstructure systems, the high yield and scalable construction of complex rolling structures with well-defined geometry without impeding functionality has remained challenging. The straightforward, one-step fabrication that uses external mechanical stress to scroll micrometer thick, flexible planar films with centimeter lateral dimensions into tubular or spiral geometry within a few seconds is demonstrated. The method allows controlling the scrolls' diameter, number of windings and nanostructured surface morphology, and is applicable to a wide range of functional materials. The obtained 3D structures are highly promising for various applications including sensors, actuators, microrobotics, as well as energy storage and electronic devices.

Efficiency increasing reconstruction of 3D‐Vessel scan data using a NURBS surface

AbstractIn this paper, a new reconstruction method using a mathematical description of the surface with non‐uniform rational B‐splines (so‐called NURBS) of 3D vessel scans is presented. With the advantage of a file size of less than 1% of the original STL file, the developed reconstruction method can be used in numerical simulations such as the placement or extension of a flow diverter. Along a generated centerline, various geometric functions can also be calculated for diagnostic purposes, such as the cross‐sectional area of the vessel, which can be used to locate a vessel stenosis. As for isogeometric analysis, this method can generally be used to reconstruct any tubular geometry.

Planar Sodium‐Nickel Chloride Batteries with High Areal Capacity for Sustainable Energy Storage

AbstractHigh‐temperature sodium‐nickel chloride (Na‐NiCl2) batteries are a promising solution for stationary energy storage, but the complex tubular geometry of the solid electrolyte represents a challenge for manufacturing. A planar electrolyte and cell design is more compatible with automated mass production. However, the planar cell design also faces a series of challenges, such as the management of molten phases during cycling. As a result, cycling of planar high‐temperature cells until now focused on moderate areal capacities and current densities. In this work, planar cells capable of integrating cost‐efficient nickel/iron electrodes at a substantially enhanced areal capacity of 150 mAh cm−2 is presented. Due to a low cell resistance during operation at 300 °C, these cells deliver a specific discharge energy of 300 Wh kg−1 at high discharge current densities of 80 mA cm−2 (C/2, 10%–100% state‐of‐charge). This results represent the first demonstration of planar Na‐NiCl2 cells at a commercially relevant combination of areal capacity, cycling rate, and energy efficiency. It is further identified the secondary molten NaAlCl4 electrolyte to contribute to the cell capacity during cycling. Mitigating electrochemical decomposition of NaAlCl4 will play an important role in further enhancing both cycling rates and cycle life of high temperature Na‐NiCl2 batteries.

State-Of-The-Art of Sandwich Composite Structures: Manufacturing—to—High Performance Applications

This cutting-edge review highlights the fundamentals, design, and manufacturing strategies used for sandwich composites. Sandwich composite structures have the advantages of light weight, high strength, impact resistance, stability, and other superior features for advanced applications. In this regard, different core materials have been used in the sandwich composite structures, such as cellular polymer foam, metallic foam, honeycomb, balsa, tubular, and other core geometries. Among these, honeycomb sandwich composite materials have been effectively applied in space engineering, marine engineering, and construction applications. The foremost manufacturing techniques used for sandwiched composite structures include hand lay-up, press method, prepreg method, vacuum bagging/autoclave, vacuum assisted resin infusion, resin transfer molding, compression molding, pultrusion, three-dimensional (3D) printing, four-dimensional (4D) printing, etc. In advanced composite manufacturing, autoclave processes have been the method of choice for the aerospace industry due to less delamination between plies and easy control of thickness dimensions. Moreover, machining processes used for sandwich composites are discussed in this article. In addition to aerospace, the high-performance significance of sandwiched composite structures is covered mainly in relation to automobile engineering and energy absorption applications. The structure-, fabrication-, and application-related challenges and probable future research directions are also discussed in this article.

Abstract Number ‐ 127: Poly(vinyl alcohol) grafts of brain aneurysms with patient‐specific morphologies

Introduction Current animal models of brain aneurysms used for testing neuro‐interventional devices have highly simplistic vascular anatomy in comparison with human aneurysm‐parent vessel complexes. Poly(vinyl alcohol) (PVA) is a leading biomaterial for manufacture of artificial vascular grafts because of its biocompatibility, hemocompatibility, availability, low cost, moldability/castability, and tunable mechanical properties to match arterial compliance [1,2]. However, PVA is non‐cell adhesive and requires modification with additives to promote endothelialization of the luminal surface to maintain long‐term graft patency [1,3]. We have previously studied the biocompatibility of resorcinol bis(diphenyl phosphate) (RDP) coated clays blended with polymers and have found excellent cell adhesion and proliferation with human dermal fibroblasts as well as dental pulp stem cells [4]. Our overall goal is to develop a new in vivo model of brain aneurysms by manufacturing patient‐specific aneurysm anatomies with a blend of PVA and RDP clay and grafting them into animals. Here, we evaluate the casting of PVA in the shape of patient‐specific aneurysms. Methods 10% PVA (w/w) (99% hydrolyzed, 85–124K molecular weight, Sigma Aldrich) was dissolved in deionized water, to which 1% RDP clay (ICL Industrial Products, Be’er Sheva, Israel) was added. The PVA was crosslinked using 15% (w/w) of sodium trimetaphosphate and 30% (w/w) of sodium hydroxide, after which rheological studies (stress sweeps using a Bohlin Gemini rheometer) were conducted. In the casting procedure, negative molds of both simple tubes and complex aneurysm geometries were designed using Rhinoceros 3D software (Robert McNeel & Associates, Seattle, WA) and 3D printed in ABS plastic. The negative mold was then filled with beeswax, resulting in a positive wax mold that was dip‐coated 8 times in PVA solution, and spun on a two‐axis spinner in between each dip to ensure even coverage. After overnight drying in a fume hood, the model was placed in heated water, allowing the wax to melt out and leaving behind the luminal PVA cast. Results Rheology on the crosslinked polymers showed that the PVA/RDP blend exhibited over twice the elastic modulus of unblended PVA (Figure A). Such enhanced mechanical properties are consistent with previous studies [5]. Both simple tubular geometries and patient‐specific anatomies were able to be successfully cast using the methodology developed here (Figure B). Conclusions This proposed casting methodology demonstrates a realistic, efficient way to replicate complex aneurysm geometries with comparatively inexpensive materials and short time frame. Future endeavors will include further exploration of the PVA/RDP biocompatibility as well as completing the casting procedure with a PVA/RDP blend.

Simple tools to monitor the anoxic condition of wastewater based on MFCs reversal signals

Microbial fuel cells have been proposed as possible alternative method to monitor organic content and other parameters of wastewaters. However, still rare, and short in-field experimentations were completed. In this work, long-term tests with two types of microbial fuel cells (planar and tubular geometry), equipped with carbon electrodes differently enriched and doped (enriched with carbon Nanotube, Ce-doped and/or undoped), were carried out in a wastewater plant (Bresso, Italy) aiming at the monitoring of the anoxic process in the tank. This experimentation aimed to improve experiences previously collected in different wastewater plants in Italy. Physico-chemical (temperature, light, redox potential) parameters were monitored during the MFCs’ operations. A hand-made automatic water sampler was used to perform some punctual chemical (COD, N, oxygen) measurements.The results indicated variable anoxic conditions in the monitored wastewater. The presence of a rich flora of protozoa on the anodes confirmed this condition. The MFCs signal was consequently very low during seasons of the year. Cathode and anode reversed, having different microbial activity on the anode and on the cathode. Next Generation Sequencing (NGS) of S16 RNA analysis gave insight on bacteria pools and the type of biofilm developing on different anodes and cathodes of MFCs.

Achieving balanced behavior between polysulfides adsorption and catalytic conversion from heterostructure Fe3C-Fe3P promotor for high-performance lithium-sulfur batteries

Although rechargeable lithium-sulfur batteries (LSBs) are next generation energy storage devices, severe shuttle effect and sluggish multi-electron redox reactions compromise the practical application of LSBs. To address these issues and enable the manufacture of robust LSBs, here the use of Fe3C-Fe3P heterostructure encapsulated in nitrogen–doped carbon nanotubes (FeCP@NCNT) was synthesized. The tubular geometry of FeCP@NCNT provided buffering void to suppress volume change, and afforded conductive network to expedite the diffusion of Li+, as well as endowed plenteous active sites to absorb and catalyze the transformation of LiPSs during charge–discharge cycles. Experimental data proved that FeCP@NCNT could strengthen the “anchoring of lithium polysulfides (LiPSs)” (by Fe3P) and expedite the “diffusion of intermediate” (by CNT) as well as accelerate the “catalytic phase conversion” (by Fe3C), resulting in balanced “trapping-diffusion-conversion” dynamic process. Notably, FeCP-3 h@NCNT/G/S attained an initial capacity of 1127 mAh/g with a low decay rate of 0.12 % at 1C for 300 cycles Moreover, FeCP-3 h@NCNT/G/S delivered excellent battery performances under high currents of 2 and 5C for 500 cycles. This work felicitously proposed the strategy to fabricate metal carbide-phosphide heterostructure electrocatalyst for high-performance LSBs.

Achieving Both Ultrahigh Electrical Conductivity and Mechanical Modulus of Carbon Films: Templating-Coalescing Behavior of Single-Walled Carbon Nanotube in Polyacrylonitrile.

Promoting the feasibility of carbon films as electrode applications requires sufficient performances in view of both electrical and mechanical properties. Herein, carbon films with ultrahigh electrical conductivity and mechanical modulus are prepared by high temperature carbonization of polyacrylonitrile (PAN)/single-walled carbon nanotube (SWNT) nanocomposites. Achieving both performances is ascribed to remarkable graphitic crystallinity, resulting from the sequential templating-coalescing behavior of concentrated SWNT bundles (B-CNTs). While well-dispersed SWNTs (WD-CNTs) facilitate radial templating according to their tubular geometry, flattened B-CNTs sandwiched between carbonized PAN matrices induce vertical templating, where the former and latter produce concentric and planar crystallizations of the graphitic structure, respectively. After carbonization at 2500 °C with the remaining WD-CNTs as microstructural defects, the flattened B-CNTs coalesce into graphitic crystals by zipping the surrounding matrix, resulting in high crystallinity with the crystal thicknesses of 27.4 and 39.4nm for the (002) and (10) planes, respectively. For comparison, the graphene oxide (GO) containing carbon films produce a less-ordered graphitic phase owing to irregular templating, despite the geometrical consistency. Consequently, PAN/B-CNT carbon films exhibit exceptional electrical conductivity (40.7× 104 S m-1 ) and mechanical modulus (38.2 ± 6.4GPa). Thus, controlling the templating-coalescing behavior of SWNTs is the key for improving final performances of carbon films.

SvMorph: Interactive Geometry-Editing Tools for Virtual Patient-Specific Vascular Anatomies.

We propose svMorph, a framework for interactive virtual sculpting of patient-specific vascular anatomic models. Our framework includes three tools for the creation of tortuosity, aneurysms, and stenoses in tubular vascular geometries. These shape edits are performed via geometric operations on the surface mesh and vessel centerline curves of the input model. The tortuosity tool also uses the physics-based Oriented Particles method, coupled with linear blend skinning, to achieve smooth, elastic-like deformations. Our tools can be applied separately or in combination to produce simulation-suitable morphed models. They are also compatible with popular vascular modeling software, such as simvascular. To illustrate our tools, we morph several image-based, patient-specific models to create a range of shape changes and simulate the resulting hemodynamics via three-dimensional, computational fluid dynamics. We also demonstrate the ability to quickly estimate the hemodynamic effects of the shape changes via the automated generation of associated zero-dimensional lumped-parameter models.

Inverse design of 3D reconfigurable curvilinear modular origami structures using geometric and topological reconstructions

The recent development of modular origami structures has ushered in an era for active metamaterials with multiple degrees of freedom (multi-DOF). Notably, no systematic inverse design approach for 3D curvilinear modular origami structures has been reported. Moreover, very few modular origami topologies have been studied to design active metamaterials with multi-DOF. Herein, we develop an inverse design method for constructing 3D reconfigurable architected structures — we synthesize modular origami structures whose unit cells can be volumetrically mapped into a prescribed 3D curvilinear shape followed by volumetric shrinkage to construct modules. After modification of the tubular geometry, we search through all the possible geometric and topological combinations of the modular origami structures to attain the target mobility using a topological reconstruction of modules. Our inverse design using geometric and topological reconstructions can provide an effective solution to construct 3D curvilinear reconfigurable structures with multi-DOF. Our work opens a path toward 3D reconfigurable systems based on volumetric inverse design, such as 3D active metamaterials and 3D morphing devices for automotive, aerospace, and biomedical engineering applications.

Nanotubular Geometry for Stabilizing Metastable 1T‐Phase Ru Dichalcogenides

AbstractOwing to their remarkable electrochemical activities, 1T phase transition metal dichalcogenide (TMD) materials have attracted considerable interest in recent decades. However, metastable 1T phases are difficult to prepare and readily change phases. Therefore, for the first time, a monolayer nanotubular 1T Ru dichalcogenide comprising 92% of the 1T phase is synthesized, which is the highest value ever obtained using solvothermal methods. In the tubular geometry, the 1T phase exhibits superior durability against various external stimuli and electrocatalytic activity toward the oxygen reduction reaction. According to density‐functional‐theory‐based and molecular dynamics calculations, sufficiently curved architectures can change their bond identities to safely maintain 1T phases, hence providing a strategy for stabilizing metastable phases. The study results form a basis for extensively applying 1T phases and will stimulate interest for applying tubular structures for stabilizing metastable materials.

Ultra-stable metallic freestanding multilayer borophene with tunable work function

This study examines the structural stability of 1–3-layer structures of seven typical borophene classes (α, α1, α5, χ3, β12, δ6, and δ3), and the results obtained indicate that α- and α5-borophene exhibits the top two favorable stability in the 1–3-layer series. Accordingly, the structural stabilities, electronic structures, and work functions of 1–5-layer α- and α5-borophene are investigated systematically. The increased binding energies (Eb) with increasing layer number for both α- and α5-borophene demonstrate that their stabilities are enhanced, as confirmed by ab initio molecular dynamics simulations. Remarkably, the interlayer bonding of α-borophene shifts from the isolated covalent dominant B–B bonds (2-layer) to 5- or 6-centered localized bonds with mixed covalent and ionic components (4-/5-layer), leading to the formation of an unprecedented interconnected 2D tubular geometry (α-type boron nanotubes), which significantly enhances the interlayer bonding strength and contributes dominantly to the increasing Eb with increasing layer number. Contrarily, the increased thermodynamic stability for α5-borophene with increasing layer number mainly originates from the increased in-plane bonding interaction. In particular, the highly stable metallic 5-layer α5- (4.54 eV) and α-borophene (5.66 eV) structures with favorable work functions are considered alternative material of graphene and highly attractive anode materials for applications in electronic devices, respectively.

Submerged Friction Stir Back Extrusion of AZ31 Magnesium Alloy

Friction Stir Back Extrusion (FSBE) is a new grade of severe plastic deformation process capable of producing metallic tubular geometries that exhibit ultrafine grain structure and superior mechanical properties. FSBE of tubular sections provide opportunities for producing lightweight rigid structures for the automotive, aerospace and construction industries. This research investigates the effect of submerging conditions (in water at 25 °C and 2 °C) for Magnesium AZ31-B tubes on the grain size, mechanical properties, temperature history and power consumption. Submerged FSBE is compared to FSBE in air at fixed process parameters of 90 mm/min and 2000 rpm. It is shown that the impact of submerging is statistically insignificant in terms of the mechanical properties, ultimate tensile strength and percent elongation, of the produced tubes according to the conducted t-tests. On the other hand, the optical microscopy results indicated finer grains at the inner wall of the seamless tubes for FSBE in air and underwater FSBE at 25 °C when compared to underwater FSBE at 2 °C.

PI4P and BLOC-1 remodel endosomal membranes into tubules.

Intracellular trafficking is mediated by transport carriers that originate by membrane remodeling from donor organelles. Tubular carriers contribute to the flux of membrane lipids and proteins to acceptor organelles, but how lipids and proteins impose a tubular geometry on the carriers is incompletely understood. Using imaging approaches on cells and in vitro membrane systems, we show that phosphatidylinositol-4-phosphate (PI4P) and biogenesis of lysosome-related organelles complex 1 (BLOC-1) govern the formation, stability, and functions of recycling endosomal tubules. In vitro, BLOC-1 binds and tubulates negatively charged membranes, including those containing PI4P. In cells, endosomal PI4P production by type II PI4-kinases is needed to form and stabilize BLOC-1-dependent recycling endosomal tubules. Decreased PI4KIIs expression impairs the recycling of endosomal cargoes and the life cycles of intracellular pathogens such as Chlamydia bacteria and influenza virus that exploit the membrane dynamics of recycling endosomes. This study demonstrates how a phospholipid and a protein complex coordinate the remodeling of cellular membranes into functional tubules.

Stability of infiltrated cathodes using Pr2NiO4+delta precursor for low-temperature fuel cell applications

The electrochemical performance and stability of infiltrated praseodymium nickelate (PNO) as the cathode for solid oxide fuel cell (SOFC) applications was studied. PNO cathode (Pr2NiO4+δ) was infiltrated into gadolinium-doped ceria (GDC) scaffolds and tested in two different anode-supported cells with tubular geometry: i) tubular cell A with Ni-YSZ support, Ni-YSZ anode functional layer (AFL), and thin (∼7 μm) electrolyte and; ii) microtubular cell B with Ni-YSZ support, without AFL and thick (34 μm) electrolyte. Both cells were stable during 91 h and 260 h of stability testing at 650 °C and experienced a reduction in total polarization resistances. Post-mortem X-ray diffraction (XRD) analysis confirmed PNO's partial transformation into the Pr4Ni3O10 phase with higher electrical conductivity and thermal stability. Improvement in the oxygen reduction reaction was confirmed using DRT analysis. This finding confirms that PNO infiltrated into GDC scaffold can be considered a promising cathode for SOFC applications.

Multi-physics modelling and simulation approach with experimental validation for electrocatalytic filtration process: Part A. Optimization of electrodeposition of metal oxides on carbon membranes

• The model helped in a fast and accurate determination of optimum parameters for uniform electrodeposition results. • The model allowed the control and manipulation of deposition parameters. • RMSE values described good agreement between the model and the experimental studies. • The model gave a generalization of the application to various metal oxides. The integration of metal oxidized catalysts on conductive membrane substrates for electrochemical filtration process is an ingenious way to improve their water treatment performance. However, the determination of the optimum parameters for a uniform distribution of the metal particles over the membrane surface conventionally necessitates multiple experiments and is even more difficult to attain uniformity when coating onto non-flat surface geometries. In this work part A of the study, based on finite element method (FEM) in combination with error control and adaptive meshing using the UMFPACK solver of COMSOL Multi-physics software, we developed a model which through simulations helped in a fast and accurate determination of optimum parameters for uniform electrodeposition results of various metals onto tubular geometry coal-based carbon membrane. Experimental studies were also conducted in order to demonstrate the accuracy of the model and the Pearson's correlation coefficient and the root-mean-square error (RMSE) obtained in this work gave values of [0.88, 0.99] and [0.01, 0.1] respectively, confirming the agreement of the model data with experimental data. The difference in optimum parameters observed for each system studied is another evidence that the model allows the control and manipulation of parameters regardless of the depositing species which marks a significant step forward accurate prediction of electrodeposition of catalysts on carbon membranes for electrocatalytic wastewater treatment.

The Construction of Biologically Relevant Fiber-Reinforced Hydrogel Geometries Using Air-Assisted Dual-Polarity Electrospinning.

Fiber-reinforced hydrogels are a class of soft composite materials that have seen increased use across a wide variety of biomedical applications. However, existing fabrication techniques for these hydrogels are unable to realize biologically relevant macro/mesoscale geometries. To address this limitation, this paper presents a novel air-assisted, dual-polarity electrospinning printhead that converges high-strength electric fields, with low velocity air flow to remove the collector dependency seen with traditional far-field electrospinning setups. The use of this printhead in conjunction with different configurations of deformable collection templates has resulted in the production of three classes of fiber-reinforced hydrogel prototype geometries, viz., (i) tubular geometries with bifurcations and mesoscale texturing; (ii) hollow, nontubular geometries with single and dual-entrances; and (iii) three-dimensional (3D) printed flat geometries with varying fiber density. All three classes of prototype geometries were mechanically characterized to have properties that were in line with those observed in living soft tissues. With the realization of this printhead, biologically relevant macro/mesoscale geometries can be realized using fiber-reinforced hydrogels to aid a wide array of biomedical applications.

Direct, efficient and selective capture of low concentration of CO2 from natural gas flue gas using a high temperature tubular carbon capture membrane

Natural gas (NG) fired power plants emit low concentration (4–5%) of CO2, which presents additional technical and economic challenges to the current benchmark amine absorption technology. The newly emerged high-temperature multiphase membranes operated on molten carbonate (MC) chemistry for CO2 capture/separation/conversion have been demonstrated with great potential to meet this challenge. In this study, we report on the CO2 capture performance of such a membrane in tubular geometry from a mockup NG flue gas. The membrane is comprised of a mixture of Gd0.20Ce0.80O1.95 (GDC) and MC, in which GDC forms a porous skeleton to contain MC. We show that the membrane with a dimension of 6.1 mm in outer diameter, 5.1 mm in inner diameter and 5 cm in effective length (resulting in 4 cm2 effective surface area) can achieve a CO2 flux density of 0.46–0.55 mL/min·cm2 at 650 °C, capturing 97% pure CO2 at a rate of 37–42% from 5%CO2–N2 using moistened Ar as the sweep gas. The level of performance demonstrated by this study suites the membrane well for stationary CO2 capture from NG power plants.

Progress and challenges on 3D tubular structures and devices of 2D materials

Due to their unique structures and properties, emerging two-dimensional (2D) materials have been at the frontier of research in, e.g., materials science, physics, and engineering. Three-dimensional (3D) tubular geometry enables 2D materials unparalleled advantages for various applications, for example, wide-angle infrared photodetectors, extremely sensitive molecular sensors, and memory with high density. Furthermore, 3D tubular structures offer a promising integration platform into chips with a broad range of materials, especially 2D materials. In this Perspective, we highlight state-of-the-art methods to assemble/manufacture 2D materials into 3D tubular structures/devices via self-rolled-up or template methods. These tubular 3D devices inspire unique physical, chemical, and mechanical properties for optical microcavity, photodetector, on-chip electronics, and bubble-propelled microengines. On-chip manufacture of 3D tubular structures/devices provides great opportunity and challenge for 2D materials for More than Moore applications such as unconventional electronics, smart sensors, and miniaturized robots.