Cylindrical Lattice Research Articles

Defect-insensitive cylindrical surface lattice resonance array and its batch replication for enhanced immunoassay.

Surface lattice resonances (SLR) have been demonstrated to enhance the sensitivity and reduce the full width at half maximum (FWHM) of the plasmonic resonances. However, their widespread application in immunoassays has been hindered by limitations of high structural defect sensitivity and fabrication costs. Here, we design a novel three-layer cylindrical SLR array that exhibits high tolerance against structural defects, which would facilitate straightforward fabrication. By integrating metal evaporation and nanoimprint lithography, we demonstrate the replication of the SLR array with exceptional quality. Theoretical simulations indicate that the resonance dips of these arrays exhibit are not sensitive to various structural defects. The experimental results reveal that the FWHM of these arrays can be as low as 5.1 nm while maintaining robust resonance characteristics. Furthermore, we demonstrated the high spectral sensitivity of the SLR array, which enabled the detection of immunoglobulin G (IgG) at concentrations as low as 609 pg/mL. These findings emphasize the potential of the defect-insensitive SLR array as a highly scalable immunoassay platform with exceptional performance.

Easy-to-use formulations based on the homogenization theory for vascular stent design and mechanical characterization

Background and objectivesVascular stents are scaffolding structures implanted in the vessels of patients with obstructive disease. Stents are typically designed as cylindrical lattice structures characterized by the periodic repetition of unit cells. Their design, including geometry and material characteristics, influences their mechanical performance and, consequently, the clinical outcomes. Computational optimization frameworks have proven to be effective in assisting the design phase of vascular stents, facilitating the achievement of enhanced mechanical performances. However, the reliance on time-consuming simulations and the challenge of automating the design process limit the number of design evaluations and reduce optimization efficiency. In this context, a rapid and automated method for the mechanical characterization of vascular stents is presented, taking the stent geometry, conceived as the periodic repetition of a unit cell, and material as input and providing the mechanical response of the stent as output. MethodsVascular stents were assumed to be thin-walled hollow cylinders sharing the same macroscopic geometrical characteristics as the cylindrical lattice structure but composed of an anisotropic homogenized material. Homogenization theory was applied to average the microscopic inhomogeneities at the stent unit cell level into a homogenized material at the macro-scale, enabling the calculation of the associated homogenized material tensor. Analytical formulations were derived to relate the stent mechanical behavior to the homogenized stiffness tensor, considering linear elastic theory for thin-walled hollow cylinders and three loading scenarios of relevance for vascular stents: radial crimping; axial traction; torsion. Validation was conducted by comparing the derived analytical formulations with results obtained from finite element analyses on typical stent designs. ResultsHomogenized stiffness tensors were computed for the unit cells of three stent designs, revealing insights into their mechanical performance, including whether they exhibit auxetic behavior. The derived analytical formulations were successfully validated with finite element analyses, yielding low relative differences in the computed values of foreshortening, radial, axial and torsional stiffnesses for all three stents. ConclusionsThe proposed method offers a rapid, fully automated procedure that facilitates the assessment of the mechanical behavior of vascular stents and is suitable for effective integration into computational optimization frameworks.

Quantum states and spectra of small cylindrical and toroidal lattices

Abstract We examine the spectrum and quantum states of small lattices with cylindrical and toroidal topology subject to a scalar gauge potential that introduces a position dependent phase in the inter-site coupling. Equivalency of gauges assumed in infinite lattices is generally lost due to the periodic boundary conditions, and conditions that restore it are identified. We trace the impact of various system parameters including gauge choice, boundary conditions and inter-site coupling strengths, and an additional axial field. We find gauge dependent appearance of avoided crossings and persistent degeneracies, and we show their impact on the associated eigenstates. Smaller lattices develop prominent gaps in spectral lines associated with edge states, which are suppressed in the thermodynamic limit. Toroidal lattices have counterparts of most of the features observed in cylindrical lattices, but notably they display a transition from localization to delocalization determined by the relation between the field parameter and the number of lattice sites.

Carbon nanotuballs: Can they drive the future of nanofibers?

Nanofibers are extremely thin fibers produced from materials such as carbon, polymers, ceramics, and metals with diameters in the nanometer range that gained significant interest due to their unique properties. Carbon nanotubes, which could be considered the most popular fibers in the nanoscale, have gained widespread recognition primarily due to their remarkable strength derived from their cylindrical hexagonal lattice formed by carbon covalent bonds. Here, a new family of carbon nanofibers is proposed, arising from the combination of the tubular hexagonal configuration of carbon nanotubes and the spherical nanostructure of carbon fullerenes. These novel nanofibers, hereafter named carbon nanotuballs, are expected to demonstrate new advantaged characteristics such as better cross-section properties, enhanced interfacial interactions, and other unique physical attributes when used as fillers within other phases. Some preliminary theoretical investigations based on molecular dynamics are provided here to test the structural stability and mechanical behaviour of some single-walled carbon nanotuballs.

Investigation of the Mechanical Strength of Artificial Metallic Mandibles with Lattice Structure for Mandibular Reconstruction.

Mandibular reconstructive surgery is necessary for large bone defects. Although various reconstruction methods have been performed clinically, there is no mandibular reconstruction method that meets both sufficient strength criteria and the patient's specific morphology. In this study, the material strength of the cylindrical lattice structures formed by electron-beam melting additive manufacturing using titanium alloy powder was investigated for mandibular reconstruction. The virtual strengths of 28 lattice structures were compared using numerical material tests with finite element method software. Subsequently, to compare the material properties of the selected structures from the preliminary tests, compression test, static bending test and fatigue test were conducted. The results showed that there were correlations with relative density and significant differences among the various structures when comparing internal stress with deformation, although there was a possibility of localized stress concentration and non-uniform stress distribution based on the lattice structure characteristics. These results suggest that the lattice structure of body diagonals with nodes and a cell size of 3.0 mm is a potential candidate for metallic artificial mandibles in mandibular reconstruction surgery.

Programmable nonreciprocal Poynting effect enabled by lattice metamaterials.

Shear nonreciprocity, implying unequal shear forces in opposite shear directions, can be achieved by arranging structures asymmetrically. However, the nonreciprocal Poynting effect, i.e., unequal normal stresses induced by the same shear displacements to the left and right, has not been fully explored. We discover the nonreciprocal Poynting effect using a generalized directional truss model. Inspired by this discovery, the cylindrical lattice metamaterials constructed from antisymmetric curled microstructures are used as a case study to generate the nonreciprocal Poynting effect. We develop a design framework that integrates digital generation, finite deformation theory, finite element modeling, and three-dimensional printing to program the nonreciprocal Poynting effect. Applications such as bionic Poynting effect matching, wave energy converter, and unidirectional motion limitation are demonstrated. This framework allows the one-to-one mapping between the torque and normal forces, paving the way for designing soft devices with precise force transmission capabilities.

Twist design of lattice structure fabricated by powder bed fusion to adjust the energy absorption behavior

Additive manufactured lattice structures offer great potential for impact resistance applications. They exhibit excellent energy absorption characteristics during the elasto-plastic deformation process, providing protection to internal devices. However, the mechanical response of lattice structures undergoes substantial variations during the deformation process, thereby imposing limitations on their energy absorption behavior. This study introduces a novel twist design to modify the energy absorption behavior of rectangular and hollow cylindrical lattice structures. Powder bed fusion was used to fabricate the twisted lattice structures. The study employed a combination of compressive simulations and experimental investigations to systematically explore the impact of the twist angle on the peak crushing force, energy absorption, and crash load efficiency of the structures. Adjusting the twist angle results in a reduction of the peak crushing force and a transition towards a stable loading profile during the deformation process. Moreover, the crash load efficiency is also reduced. The twist design concept presented in this paper provides insight into designing and optimizing lattice structures for energy absorption applications.

Bilinear stiffness and bimodular Poisson's ratio in cylindrical sinusoidal lattices through topology morphing

Bilinear elastic behaviour allows structural designs to respond in either a stiff or compliant manner depending on the load. Here a cylindrical sinusoidal lattice structure is described that stiffens beyond a certain load. When subjected to axial compression, the lattice can undergo a topological transformation by forming contact connections. This topology change involves a transition from rectangular-like unit cells to kagome-like unit cells, associated with an approximately fourfold increase in stiffness. The lattice exhibits negative Poisson's ratio with a step-change from ≈−0.66 to ≈−0.23 prior to and during contact formation, respectively. After contact formation, it displays a nonlinear Poisson's ratio behaviour. The mechanics underpinning these behaviours are analysed using a combination of experiments and numerical modelling. A comparison with similar planar lattices reveals the effect of the global topology of the lattice (e.g. planar, cylindrical) on the unit cell-level topology morphing. The proposed topology-morphing cylindrical sinusoidal lattice introduces new design possibilities in the application-rich context of tubular structures with nonlinear mechanical properties.

Numerical study on heat transfer deterioration of supercritical CO2 in lattice structure array channel

This study numerically explores the fluid flow and heat transfer features of supercritical carbon dioxide (CO2) in lattice structure array channel. The mitigation mechanism of the miniature cylindrical lattice structure array on heat transfer deterioration (HTD) of supercritical CO2 in vertically upward heated channel is studied. This paper evaluates the effect of several key influential parameters (length, diameter, pitch and number) of cylindrical lattice structure array on fluid flow field involving vortex structures, heat transfer coefficient, buoyancy effect and accelerated effect. The results indicate that the lattice structure can effectively suppress the HTD by generating the vortex structure which promoting the turbulent mixing effect and enhancing the turbulent kinetic energy (TKE) of the fluid. Compared with the smooth channel, the peak wall temperature of the lattice structure channel is reduced by about 50 °C, with a corresponding increase in the heat transfer coefficient of about 140 %. The average heat transfer coefficient of the channel is increased by more than 1/3. Furthermore, by increasing lattice length can reduce flow layer stratification and by increasing lattice diameter can creating a composite vortex, which enhance flow mixing strength. The larger the lattice pitch, the worse the overall suppression effect. A denser lattice arrangement produces more temperature valleys, thereby increasing the heat transfer coefficient. The conclusions in this study could provide the main theory support for security and stability of supercritical CO2 heat exchangers in power system.

Comparison of the Bending Behavior of Cylindrically Shaped Lattice Specimens with Radially and Orthogonally Arranged Cells Made of ABS.

The article deals with the comparison of the bending behavior of cylindrical lattice samples with radially and orthogonally arranged cells made of ABS material. The structures were designed in PTC Creo Parametric 8 software, while four types of lattice structures were evaluated: Rhombus, Cuboidal BCC, Octagon, and Starry, in three material volume fractions: 44, 57, and 70%, together with tubular and rod-shaped samples. The Fused Filament Fabrication (FFF) technique was chosen for the production of ABS plastic samples. Based on the bending tests, the dependences of the force on the deflection were recorded and the obtained data were statistically processed to identify outliers using the Grubbs test. The maximum stresses were calculated and the dependences of the stresses on the volume fractions were plotted. Along with energy absorption, ductility indices were also specified. Although the Rhombus structure appears to be the best based on the ductility indices obtained, on the other hand, the structure showed the lowest values of bending stresses (in the range from 10.6 to 12.6 MPa for volume fractions ranging from 44 to 70%, respectively). Therefore, from a synergic point of view of both factors, stress and ductility, the Starry structure exhibits the best flexural properties among those investigated.

Radial nanotubes for nanoelectronics elements: structure and diffraction

Formulation of the problem. Nanotubes are promising objects for the development of nanoelectronic elements. The range of electronic properties of nanotubes can be significantly expanded by synthesizing structures on their surface. Such structures have a radial cylindrical lattice; a number of nanowires have a similar lattice. Radial crystals are a new group of cylindrical structures, the study of which is at an early stage. Therefore, it is necessary to develop both ideas about the structure of radial crystals and a method for their structural analysis. The aim. Consider the simplest radial structures and the features of diffraction by them. Results. A description of the close-packed structure of nanowires and atomic layers with bcc, fcc, and hcp radial lattices sorbed on the nanotube surfaces is proposed, taking into account the effect of radial relaxation. A linear approximation is proposed that makes it possible to quantitatively describe radial relaxation at the initial stage of block growth. The quantitative kinematic theory of Fraunhofer diffraction on achiral radial structures is considered as the basis for their structural analysis, and formulas relating the parameters of the direct and reciprocal lattices are obtained. The results of model calculations of scattering intensity distributions by layer planes of the reciprocal lattice of radial crystals and along the layer lines of their diffraction patterns are presented. Schemes of diffraction patterns of radial crystals with bcc, fcc, and hcp radial lattices are presented. The applicability of traditional selection rules and the significant dependence of the positions of pseudo-orthogonal reflections on the crystal size are shown. Practical significance. The proposed description of radial structures with bcc, fcc, and hcp radial lattices and the diffraction method of structural analysis of their achiral varieties will provide structural control of the products of their synthesis, which is necessary when carrying out a wide range of studies both at the stage of development work on the synthesis of nanoelectronic elements, and for technological control during their industrial production.

Atg18 oligomer organization in assembled tubes and on lipid membrane scaffolds

Autophagy-related protein 18 (Atg18) participates in the elongation of early autophagosomal structures in concert with Atg2 and Atg9 complexes. How Atg18 contributes to the structural coordination of Atg2 and Atg9 at the isolation membrane remains to be understood. Here, we determined the cryo-EM structures of Atg18 organized in helical tubes, Atg18 oligomers in solution as well as on lipid membrane scaffolds. The helical assembly is composed of Atg18 tetramers forming a lozenge cylindrical lattice with remarkable structural similarity to the COPII outer coat. When reconstituted with lipid membranes, using subtomogram averaging we determined tilted Atg18 dimer structures bridging two juxtaposed lipid membranes spaced apart by 80 Å. Moreover, lipid reconstitution experiments further delineate the contributions of Atg18’s FRRG motif and the amphipathic helical extension in membrane interaction. The observed structural plasticity of Atg18’s oligomeric organization and membrane binding properties provide a molecular framework for the positioning of downstream components of the autophagy machinery.

Additive manufacturing TPMS lattice structures: Experimental study on airflow resistivity

Triply periodic minimal surface structures (TPMS) are continuously adopted in the architectural engineering and aircraft sectors in pursuit of noise mitigation. The airflow resistivity significantly influences the acoustic performance of lattice structures. The present work is a step toward designing appropriate structures of TPMS to obtain desired acoustics performance using the standard of ISO 9053–1:2018(E). In this work, the four TPMS lattices Gyroid, Diamond, Lidinoid, and Split P have been designed with three different parameters (porosity, sample length, and diameter) to predict the airflow resistivity and pressure drop of the structures. Various experiment sets were conducted on customized airflow resistivity experimental apparatus for cylindrical lattices with multiple parameters to identify the most effective lattice structures. Based on the findings, it was observed that lattice structures with less porosity, sample length, and sample diameter depict the highest level of airflow resistivity and pressure drop. However, for all four lattices, close differences in airflow resistivity values were noticed.

Radially and axially graded cellular tibial stems for total knee replacement

In spite of the high success rate of existing total knee replacement implants, the aseptic loosening of components, particularly the tibial one, is a matter of concern. To control the short- and long-term loosening mechanisms, the tibial stem material shall have diverse stiffness properties in different regions and directions, such that it encourages osseointegration and prevents bone resorption. The previous studies in the literature have failed to provide designs which could satisfy these two requirements concurrently. The purpose of this study was to design heterogeneous and anisotropic porous titanium tibial stems, based on radial and axial functionally graded cellular (FGC) structures, with precisely tailored stiffness properties. A 3D voxel-based finite element model of the bone-implant construct was developed to predict the nodal micromotion at the interface, assuming a frictional contact, and the stress-shielding effect in the periprosthetic bone, assuming a perfectly bonded connection. An exponential FGC material model was assigned to the implant along each of the radial and axial directions, with the gradient parameters considered as design variables. A design of experiment (DOE) -based multi-objective optimization procedure was then employed to maximize the osseointegration potential and minimize the bone resorption index. Equivalent FGC lattices, composed of Cartesian and cylindrical arrangements of gyroid unit cells, were produced for the optimal designs and fabricated by selective laser melting (SLM) technique. In comparison with the solid stem, the radial graded design resulted in a substantial improvement in the bone resorption behavior (19.4%), but a moderate reduction in the osseointegration potential (9.4%). The axial graded design, on the other hand, was associated with a moderate improvement in the bone resorption characteristics (12.0%) and slight improvement in the osseointegration index (2.2%). The dimensional accuracy of the SLM-fabricated specimens was reasonably high (strut thickness: 0.032 to 0.076 mm RMSE, pore size: 0.029 to 0.057 mm RMSE). The radial and axial graded specimens behaved as brittle and ductile materials, respectively, in axial compression tests and failed due to buckling and excessive plastic deformation. The cylindrical lattice arrangement demonstrated a lower elastic modulus (radial graded: 1945 vs. 3053 MPa, axial graded: 779 vs. 2324 MPa) and yield strength (radial graded: 77 vs. 114 MPa, axial graded: 17 vs. 43 MPa) than the Cartesian arrangement. It was concluded that an optimal bi-directional axial and radial gradient structure with a cylindrical lattice arrangement would provide the most favorable biomechanical performance for the tibial stem.

Progressive failure analysis of anisogrid cylindrical composite lattice structure with manufacturing defects

This study performs a compression test of a cylindrical composite lattice structure and numerically investigates the failure process and behavior. Prior to the test and analysis, the distributions of the fiber tow, matrix, and manufacturing defects were observed and measured in cross-sectional images. A progressive failure analysis that considers different matrix pocket lengths and void contents was performed to examine the effects of manufacturing defects on the compressive strength. The intersecting fiber tow and matrix pocket was modeled using a continuum element and the geometry measured in the cross-sectional image. A cyclically symmetric boundary condition was applied to the symmetric model. Fracture energy-based damage evolution for the fiber tow and cohesive zone modeling for the interface failure were employed. The failure behaviors of the different damage models were compared, and the progressive failure analysis model was verified by comparing it with the test results. The results of the progressive failure analysis, considering manufacturing defects, were similar to the test results.

Compressive strength prediction of composite lattice structure using compression test results of subelement specimens

A cylindrical structure used in a space launch vehicle should endure the compressive load and it must satisfy the requirement of compressive strength. For the light-weight of the structure and improving the performance of launch vehicle, a cylindrical structure reinforced by composite lattice can be used. Therefore, a compressive strength prediction technique of the cylindrical composite lattice structure is required. In this paper, the failure criterion was proposed using the compression test of a composite lattice subelement and a simple finite element analysis for the subelement. The failure criterion was introduced using the effect of the out-of-plane and in-plane bending deformation of the rib constituting the grid of structure on the compressive strength. The subelement specimen was prepared from two different structures and the compression test was performed using several fixture jigs which can generate various deformation of the specimen. The test results and finite element model were used to examine the effect of out-of-plane and in-plane bending deformation of the rib on the compressive strength and the failure criterion which can predict the compressive strength was derived using the relationships between each parameter. The compressive failure load of the cylindrical composite lattice structure was predicted by using the proposed method and the validity and accuracy of this method were verified through a comparison of the predicted results with the test results. It was possible to predict the compressive strength within a 5% error of the experimental result.

Determining of composite cylindrical lattice equivalent stiffness characteristics considering ribs bending and shear strain

Determining of composite cylindrical lattice equivalent stiffness characteristics considering ribs bending and shear strain

Mechanical Properties of LPBF-Built Titanium Lattice Structures—A Comparative Study of As-Built and Hot Isostatic Pressed Structures for Medical Implants

We compare different lattice structures with various elementary cell sizes built by laser powder bed fusion with and without hot isostatic pressing as post treatment. Cylindrical lattice structures are mechanically tested upon static and dynamic load in order to achieve high elasticity, high fracture strength and a high number of cycles to failure with respect to applications as medical implants. Evaluating the Young’s modulus, a high stiffness for the body diagonal structure and a low fracture stress for the G-structure are measured. Hot isostatic pressing results in a higher Young’s modulus and is ambiguous in terms of fractural stress. While samples without hot isostatic pressing reveal a shear fracture, the hot isostatic pressed samples have a high ductile area where the lattice layers are wrapped and pressed into the underlying layers without a fracture. Under dynamic load, the samples without hot isostatic pressing mostly are unable withstand 106 cycles at typical loads of the human body. Hot isostatic pressing has no significant influence on the strength at high loads and low cycle numbers, but at low loads all samples survived 106 cycles. As a consequence, dode-thick and rhombic dodecahedrons with 2 mm and 1.5 mm lattice size after hot isostatic pressing are recommended for medical implants because of the high elasticity, high fracture stress and high resistance against dynamic loads, which fulfill implant requirements.

Curvature as an external field in mechanical antiferromagnets

A puckered sheet is a freestanding crystalline membrane with an embedded array of bistable buckled units. Recent work has shown that the bistable units behave like spins in a two-dimensional compressible Ising antiferromagnet with, however, a coupling to flexural phonons. At finite temperature, this purely mechanical system displays Ising-like phase transitions, which drive anomalous thermal expansion. Here, we show that geometry can be used to control phase behavior: curvature produces a radius-dependent "external field" that encourages alignment between neighboring "spins," disrupting the ordered checkerboard ground state of antialigned neighbors. The effective field strength scales as the inverse of the radius of curvature. We identify this effective field theoretically with both a discrete real space model and a nonlinear continuum elastic model. We then present molecular dynamics simulations of puckered sheets in cylindrical geometries at zero and finite temperature, probing the influence of curvature on the stability of configurations and phase transitions. Our work demonstrates how curvature and temperature can be used to design and operate a responsive and tunable metamaterial at either the macroscale or nanoscale.

Cost-effective micro-CT system for non-destructive testing of titanium 3D printed medical components

Micro-CT imaging can be used as an effective method for non-destructive testing (NDT) of metal 3D printed parts-including titanium biomedical components fabricated using laser powder-bed-fusion (LPBF). Unfortunately, the cost of commercially available micro-CT scanners renders routine NDT for biomedical applications prohibitively expensive. This study describes the design, manufacturing, and implementation of a cost-effective scanner tailored for NDT of medium-size titanium 3D printed biomedical components. The main elements of the scanner; which include a low-energy (80 kVp) portable x-ray unit, and a low-cost lens-coupled detector; can be acquired with a budget less than $ 11000 USD. The low-cost detector system uses a rare-earth phosphor screen, lens-coupled to a dSLR camera (Nikon D800) in a front-lit tilted configuration. This strategy takes advantage of the improved light-sensitivity of modern full-frame CMOS camera sensors and minimizes source-to-detector distance to maximize x-ray flux. The imaging performance of the system is characterized using a comprehensive CT quality-assurance phantom, and two titanium 3D-printed test specimens. Results show that the cost-effective scanner can survey the porosity and cracks in titanium parts with thicknesses of up to 13 mm of solid metal. Quantitatively, the scanner produced geometrically stable reconstructions, with a voxel size of 118 μm, and noise levels under 55 HU. The cost-effective scanner was able to estimate the porosity of a 17 mm diameter titanium 3D-printed cylindrical lattice structure, with a 0.3% relative error. The proposed scanner will facilitate the implementation of titanium LPBF-printed components for biomedical applications by incorporating routine cost-effective NDT as part of the process control and validation steps of medical-device quality-management systems. By reducing the cost of the x-ray detector and shielding, the scan cost will be commensurate with the overall cost of the validated component.