Unit Cell Size Research Articles

TPMS-Gyroid Scaffold-Mediated Up-Regulation of ITGB1 for Enhanced Cell Adhesion and Immune-Modulatory Osteogenesis.

The porous structure is crucial in bone tissue engineering for promoting osseointegration. Among various structures, triply periodic minimal surfaces (TPMS) -Gyroid has been extensively studied due to its superior mechanical and biological properties. However, previous studies have given limited attention to the impact of unit cell size on the biological performance of scaffolds. In this research, four TPMS-Gyroid titanium scaffolds with different unit cell sizes (TG15, TG20, TG25, and TG30) are fabricated using Selective Laser Melting (SLM) to explore their effects on osseointegration. Mechanical tests revealed that TG15 and TG20 exhibited superior compressive strength. In vitro experiments demonstrated that TG20 facilitated better cell adhesion through robust integrin protein expression initially, which subsequently enhanced cell proliferation and osteogenic differentiation. Furthermore, macrophages on TG20 showed higher Integrin β1 (ITGB1) expression, promoting their polarization to the M2 phenotype, which suppressed inflammation, fostered bone integration, and angiogenesis. In vivo studies confirmed TG20's effectiveness in promoting bone ingrowth by reducing inflammation. This study highlights TG20's structural advantages, making it a promising bone scaffold with exceptional osteogenic and angiogenic properties through osteoimmune microenvironment modulation. Therefore, TG20 holds significant potential for applications in bone tissue engineering.

High-Quality Factor Ultrathin Polarization-Insensitive Wide Angular Stable Elliptical-Shaped Microwave Absorber with Reconfigurability Features

This paper introduces an ultrathin, polarization-insensitive, wide angular stable microwave absorber characterized by a high-Quality (Q) factor. The absorber consists of elliptical metallic rings with a thickness of 0.035 mm on the top of Roger’s RT 5880 substrate with a thickness of 0.51 mm and a metallic ground plane with a thickness of 0.035 mm at the bottom. The proposed structure is fourfold symmetric which makes it polarization insensitive. The structure offers angular stability till 60° for the angle of incidence for both Transverse Electric (TE) and Transverse Magnetic (TM) modes under oblique incidence. The structure provides a high-quality factor of 155 at an operating frequency of 7.75 GHz. Also, the structure provides reconfigurability with a change in the axis ratio of the elliptical structure from 7.30 to 9.48 GHz when the axis ratio changes from 0.26 to 0.36 without any change in the unit cell size. The unit cell dimension is 1.07 λg x 1.07 λg x 0.022 λg. With its high Q-factor, thin size, structural simplicity, insensitivity to polarization, and incident angle stability suggested prototype is apt for microwave sensors and antennas to reduce Radar cross-section and X-band satellite communication.

MXene-based multilayered and ultrawideband absorber for solar cell and photovoltaic applications

We proposed the ultrawideband solar absorber using the multisized metal resonator oriented on the top of the multilayered Metal-SiO₂-MXene-MgF₂-Tungsten structure. We have carried out a numerical investigation of this structure for the 100–2500 THz frequency, which covers the infrared, visible, and UV spectra. The proposed solar absorber is numerically investigated for the different physical parameters, such as the height of the layers, unit cell size, and resonator orientation, to identify optimized results for the high absorption capacity. The structure presented in the study shows promise, with an average absorption of 80% over the large frequency spectrum of 100–2500 THz. This structure was also investigated for the variation in oblique incident angle, which showcases the absorption stability up to 60⁰ of the incident angle. We have also reported the comparative analysis for this proposed absorber structure with other designs, demonstrating the absorption efficiency over infrared, visible, and UV spectra. The proposed structure and discrete resonator length can offer a better solution for trapping the different frequency ranges, resulting in high absorption over a wideband frequency. This study can be applied to designing highly efficient parasitic solar absorber structures, which are essential to highly efficient photovoltaic and solar cell design.

High-strength of additive-manufactured PEEK and Ti6Al4V structure via warm isostatic pressing: applications in medical implants and injection moulds

ABSTRACT Polymer–metal hybrid structures offer synergistic benefits in mechanical property control and lightweight design, making them valuable across various industries. In this study, we designed and developed a warm isostatic pressing (WIP) to fabricate a hybrid structure using additive-manufactured polyetheretherketone (PEEK) and Ti-6Al-4V (Ti64) with an octet-truss lattice structure (OT). The effects of the WIP temperature on the mechanical properties of PEEK were examined by subjecting the parts to different temperatures during the WIP and performing tensile tests. Additionally, to confirm the mechanical properties of Ti64 with OT, we performed a compression test according to the unit cell size (1, 2, 3 mm) at a density of 30% before and after the WIP. Accordingly, we joined a PEEK with superior tensile strength and Ti64 with OT using a WIP under the condition (330°C and 90 bar). Furthermore, we confirmed the superior joint strength of approximately 71.6–74.8% in terms of the tensile and shear strengths of the PEEK-Ti64 hybrid structures compared to the warm isostatic pressed PEEK. Finally, we demonstrated the feasibility of applying PEEK-Ti64 hybrid structures to biomedical implants such as spinal cages and lightweight injection moulds highlighting the potential in advanced manufacturing.

Comprehensive analysis of the compressive behavior of Fischer-Koch-S, F-RD, and neovius TPMS cellular structures in 3D-printed PLA specimens

This paper investigates the compression-tested mechanical properties of 3D Polylactic acid (PLA) printed Triply Periodic Minimal Surfaces (TPMS) lattice structures, exploring the impact of varying input parameters. The input parameters included in this study are cellular structure, printing speed, and unit cell size. This study serves as a valuable guide for achieving specific mechanical properties through the selection of optimal parameters. The three input parameters would have a major effect in the overall mechanical properties of the specimens. Four output parameters were studied in this experiment elastic modulus, yield stress, plateau stress, and toughness. A Desirability Function Analysis (DFA) was implanted to achieve the most optimal parameter combination and it was compared to the original parameters. By comparing the mechanical properties of the original nine samples against the predicted optimized parameter, the toughness was increased by 2.15%, elastic modulus increased by 108.33%, yield stress increased by 4% and plateau stress increased by 3.97%.

Bandwidth enhancement of resonating absorber using a lossy dielectric layer for RCS reduction in X-band

Abstract In this paper, a resonating absorber is proposed for radar cross section reduction in the X-band, with the inclusion of a high loss dielectric layer. The absorber consists of a pair of co-centered resonating Jerusalem cross printed on a FR4 substrate cascaded with a high-loss dielectric layer and a metallic back plane. The designed absorber offers 90 % absorption from 7.8–12 GHz with a fractional bandwidth of 42.42 %. The designed absorber is 0.106λ L thick with a compact square unit cell of size 0.076λ L (wavelength at the lowest frequency). An equivalent circuit model is developed to analyze the proposed absorber. The absorber is angularly stable for varying angle of incidences up to 40°–60° for TE and TM polarizations respectively. The planar as well as the conformal structure of the proposed absorber offer a minimum 10 dB radar cross section reduction in the X-band. The conventional approach which involves complex fabrication process of soldering thousands of lumped resistors to increase the bandwidth, whereas the proposed absorber is realized to offer wide absorption using simple PCB etching technique. To validate the design prototype is fabricated and the measurement is carried out.

Defect Crystal Formation and Thermal-Induced Structural Ordering of Semicrystalline Copolymers Induced by Comonomer Inclusion/Exclusion.

Comonomer defects can induce semicrystalline polymers to form unique crystalline structures (e.g., defect crystals), which can greatly influence the materials' physical properties. However, the formation mechanism and structural evolution of defect polymer crystals are not yet well understood. Herein, we chose the poly(l-lactic acid) (PLA) containing glycolic acid (GA) units as the model defect-containing polymer and investigated its crystallization structure and phase transition. The presence of GA units reduces the crystallizability of PLA and leads to the formation of unique defect crystals with enlarged unit cell size. The formation of defect crystals is favored at a low crystallization temperature or high content of GA units due to the inclusion of more comonomer defects. The defect crystals are metastable and undergo structural ordering to form thermally stable α-crystals upon heating and high-temperature annealing, as governed by the exclusion of comonomer defects. This work sheds light on the crystallization and phase transition of defect-containing polymers.

Research on the miniaturization method of the broadband linear-to-circular polarization conversion metasurface based on genetic algorithm

The size of the metasurface unit cell increases with the decrease of its center working frequency (CF). This is not conducive to the integrated design of the metasurface. To address the problem, a miniaturization design method based on genetic algorithm (GA) is proposed. Firstly, an element library is established. By randomly selecting and combining these elements, various structures are generated as the initial population of GA. Secondly, a Python-CST joint simulation program is constructed to automatically model the metasurface unit cells and extract their electromagnetic parameters. Finally, after multiple iterations of optimization, the optimized unit cell is obtained. This paper takes the transmissive-type linear-to-circular polarization conversion metasurface (LTCPCM) as a research object. The simulation results show that the size of the designed unit cell is only 0.18 λ of the CF (3.86 GHz). The LTCPCM exhibits broadband and wide-angle characteristics, with a fractional bandwidth (FB) of 71% (incident angle θ = 0°) and an angular stability (AS) of 45°. The experimental validation and the simulation result are consistent, proving the effectiveness of the proposed method. The research results can provide a reference for further miniaturization design of metasurface unit cells.

Achromatizing photolithographically patterned metasurfaces with arbitrary, variable unit cell size

In recent years, across many fields, a large emphasis has been placed on the development of optical materials that can realize arbitrary control over the phase, transmission, and polarization of light, particularly across a broad wavelength range. Metasurface optics, or arrays of subwavelength structures with highly tailorable geometry and composition on a thin substrate, have emerged as a promising contender to fulfill these needs. Several methods for the achromatization of metasurfaces have been demonstrated, including the use of amorphous nanopost shapes as well as multiple, simple nanopost shapes. We present what we believe to be a novel technique that can be used separately or in conjunction with these techniques to provide achromatic phase control: arbitrary aperiodicity. By varying the period, or spacing between adjacent nanoposts, metasurfaces can be demonstrated that achieve desirable phase behavior and high transmission over a relatively large bandwidth. We detail the design and fabrication of such a device, in the form of a 1 cm diameter polarization insensitive metasurface with a vortex phase profile that exhibits achromatic behavior over a ∼12% bandwidth centered at 1650 nm. We demonstrate simulated phase residuals below 0.4 rad and transmission above 85% for this bandwidth, as well as measured phase residuals below 0.6 rad and transmission above 88% for this bandwidth. By showing that we can create such a device with deep-UV photolithographic fabrication techniques, we make clear the fidelity of our aperiodic technique in realizing mass-manufactureable, large-area achromatic metasurfaces for the near-infrared.

Photopatterned Anchoring Stabilizing Monodomain Blue Phases.

Blue phase liquid crystals (BPLCs) are chiral self-assembled three-dimensional (3D) periodic structures which have attracted a lot of attention due to their electro-optical properties, relevant for tunable soft photonic crystals and fast-response displays. However, to realize this application potential, controlling the BPLC alignment at the surfaces is crucial, and one way to obtain the desired alignment is by photoalignment patterning. In this article, monodomain BPLC samples with controlled orientation are achieved by imposing different alignment patterns that have a periodicity that is compatible with the size of the BPLC unit cell, using two-step photoalignment with polarized ultraviolet (UV) light. Experiments are complemented by numerical simulations to design striped surface alignment patterns, which induce specific director orientations on the boundary layer of the confined BPLC. By designing the patterns and matching the periodicity to a specific BP material, we can control the orientation of the blue phase unit cell lattice in the sample, including the azimuthal angle. The orientation is measured by the Kossel patterns and matches the optimal configuration predicted by stability analysis using Landau-de Gennes free energy modeling. The detailed structure and reduced symmetry of the BP near the surface are investigated, and the corresponding (meta)stable structures are demonstrated. Overall, we demonstrate that two-step photoalignment patterning is a reliable, relatively simple, and reconfigurable method to achieve a high-quality monodomain BP with controlled and tunable crystalline orientation.

Design and optimization of additive manufactured Fischer-Koch-structured heat exchanger for enhanced heat transfer efficiency

The study explores using triply periodic minimal surfaces (TPMS) to enhance heat exchanger efficiency and reduce flow resistance. By leveraging TPMS's high surface area and minimal curvature, a range of compact heat exchangers with different unit cell sizes was developed for thermal-hydraulic analysis. The Fischer-Koch (FK) S structure, a TPMS model, was used to precisely control design parameters like porosity and surface area. Selective Laser Melting (SLM) facilitated the creation of complex geometries, which were analyzed through numerical simulations and experiments. Results showed a strong link between Nusselt (Nu) and Reynolds (Re) numbers for the FK structure. The smallest unit cell (6 mm) achieved the highest heat transfer rate and specific volume heat transfer of 140 W/cm3, a notable industry advancement. A “Light” configuration reduced the heat exchanger's volume by 28 % without affecting thermal performance, indicating a new direction for efficient, lightweight designs.

Kernel polynomial method for linear spin wave theory

Calculating dynamical spin correlations is essential for matching model magnetic exchange Hamiltonians to momentum-resolved spectroscopic measurements. A major numerical bottleneck is the diagonalization of the dynamical matrix, especially in systems with large magnetic unit cells, such as those with incommensurate magnetic structures or quenched disorder. In this paper, we demonstrate an efficient scheme based on the kernel polynomial method for calculating dynamical correlations of relevance to inelastic neutron scattering experiments. This method reduces the scaling of numerical cost from cubic to linear in the magnetic unit cell size.

Mechanical behavior of reinforced Al2O3 lattice structures: Effects of structural parameters from experiments and simulations

The pressure hull is one of the core components of autonomous underwater vehicles (AUVs), necessitating a new structural material with improved mechanical and lightweight properties. For this purpose, a novel type of reinforced lattice structure (RLS) that integrates Al2O3 lattice structures (ALSs) with phenol-formaldehyde (PF) resin was designed and fabricated via stereolithography (SL)-based additive manufacturing and infiltration processes. The responses of the RLSs with different structural configurations, relative densities, and unit cell sizes under compressive loading were systematically characterized. Additionally, numerical simulations were conducted to further predict and study the mechanical behavior of the RLSs using Johnson-Holmquist-II (JH-2) model. The results revealed that the mechanical properties of the RLSs from superior to inferior were simple cubic (SC), body-centered cubic (BCC), Gyroid, octet truss (Oct), and SchwarzP (Sch). As the relative density and the unit cell size increased, the mechanical properties of the RLSs increased. Furthermore, the results of the numerical simulations closely aligned with the experimental results, which provided an in-depth analysis of internal damage and crack propagation in the RLSs under compression. A comparison of the mechanical properties also demonstrated that RLSs exhibit superior compressive strength and energy absorption performance than traditional ALSs do. After this investigation, this type of RLS is anticipated to facilitate lightweighting of AUVs, advancing the development of deep-sea scientific research.

Influence of Transition-Metal Order of Lnmo Spinel on Li Ion Diffusion and Thermodynamics of LNMO

A key strategy to enhance the energy density and improve the sustainability of cathode active materials for lithium-ion batteries (LIBs) is to develop more cost-effective, cobalt-free, higher-energy-density alternatives. The LiNi0.5Mn1.5O4 (LNMO) spinel phase is a promising cathode active material for LIBs as it is Co-free chemistry and exhibits a high specific energy density of 650 Wh/kg, which is attributed to its high operating voltage of approximately 4.7 V vs. Li+/Li. LNMO exists in two phases depending on the ordering of transition metals (TM) in the crystal lattice. In the disordered phase, Ni and Mn ions are randomly distributed on the 16d sites of the Fd3̅m cubic unit cell, whereas in the ordered phase, the Ni and Mn atoms occupy the 4b and 12d sites of the P4332 cubic cell, respectively. In this work, a commercially available, disordered LNMO sample was used as the starting point of the investigations. To initiate the ordering of the Ni and Mn ions, the disordered LNMO was subjected to heat-treatment at 650°C in air. The impact of transition metal (TM) ordering on fundamental parameters such as the unit cell size, electrode expansion, and Li-ion diffusion coefficients at different states of charge were explored using in-operando x-ray diffraction (XRD), in-situ dilatometry, galvanostatic intermittent titration technique (GITT), and electrochemical impedance spectroscopy (EIS) measurements. The electrodes for these studies were prepared using both PVDF and water-based binders in order to gain key insights into the effect of aqueous electrode processing on the Li+-ion transport parameters, interface resistances, and electrode expansion during cycling.Furthermore, a thermodynamic dataset containing the Gibbs free energy description of the LNMO phase was used to calculate the open circuit voltages and lattice parameters of crystalline LNMO as a function of state of charge and Ni and Mn contents in LNMO. The results of the calculations were compared to those from our experimental investigations to assess the predictive quality of the thermodynamic simulations. Our results show a good agreement between the calculated and quasi-equilibrium open circuit voltages measured by GITT and during cycling. In addition, the experimentally determined volume change of the crystal lattice during intercalation and de-intercalation of Li, as measured by in-operando XRD, was well reproduced by the thermodynamic simulation. Therefore, the second aspect of this work, focused on the thermodynamics of LNMO, shows that Gibbs free energy descriptions of cathode active materials can be used to model and assess their electrochemical performance and structural behaviour during cycling.

Single Electron Self-coherence and Its Wave/Particle Duality in the Electron Microscope.

Intensities in high-resolution phase-contrast images from electron microscopes build up discretely in time by detecting single electrons. A wave description of pulse-like coherent-inelastic interaction of an electron with matter implies a time-dependent coexistence of coherent partial waves. Their superposition forms a wave package by phase decoherence of 0.5 - 1 radian with Heisenbergs energy uncertainty ΔEH = ħ/2 Δt-1 matching the energy loss ΔE of a coherent-inelastic interaction and sets the interaction time Δt. In these circumstances, the product of Planck's constant and the speed of light hc is given by the product of the expression for temporal coherence λ2/Δλ and the energy loss ΔE. Experimentally, the self-coherence length was measured by detecting the energy-dependent localization of scattered, plane matter waves in surface proximity exploiting the Goos-Hänchen shift. Chromatic-aberration Cc-corrected electron microscopy on boron nitride (BN) proves that the coherent crystal illumination and phase contrast are lost if the self-coherence length shrinks below the size of the crystal unit cell at ΔE > 200 eV. In perspective, the interaction time of any matter wave compares with the lifetime of a virtual particle of any elemental interaction, suggesting the present concept of coherent-inelastic interactions of matter waves might be generalizable.

A high-performance ultra-compact plasmonic metamaterial structure for optical THz absorption

This study presents the design and analysis of a high-performance metamaterial absorber for the optical terahertz (THz) regime. The proposed absorber utilizes a unique nested flower-shaped structure composed of nickel (Ni) and silicon dioxide (SiO2), achieving an average absorption exceeding 97.91% with a broad bandwidth of 1320 THz (180 THz − 1500 THz). A unit cell size of 66 nm × 66 nm × 24 nm makes this design highly attractive for miniaturized devices. Strong absorption originates from localized surface plasmon resonance (LSPR), where light interacts with the electrons on the Ni surface. Notably, the design maintains excellent absorption performance even at oblique incident angles up to 60° with polarization insensitivity. These results highlight the Ultra-Compact Plasmonic Metamaterial (UCPM) absorber’s potential for diverse applications due to its broad spectral response, high absorption efficiency, and minimal footprint, making it valuable for energy harvesting, infrared imaging, and electromagnetic stealth technologies.

Mechanical properties of diamond-type triply periodic minimal surface structures fabricated by photo-curing 3D printing

Triply periodic minimal surface (TPMS) structures have attracted significant attention owing to their smooth surface configuration and parametric modeling properties. In this study, photo-curing 3D printing was employed to generate diamond-type TPMS structures, and micro-CT scanning revealed the presence of internal defects within the 3D printed TPMS structures. Two key design variables were explored: volume fraction and unit cell size. Quasi-static compression experiments were conducted to delve into the compression properties and energy absorption capabilities of the 3D printed TPMS structures. The findings reveal that increasing the volume fraction significantly enhances the compressive modulus, ultimate strength, and energy absorption capacity of TPMS structures. Additionally, increasing the cell size improves compression properties and energy absorption per unit volume. To predict the coupling effect of volume fraction and unit cell size on the compression performance of TPMS structures, a bivariate quadratic regression model was established. In addition, TPMS structures were subjected to load-unload cyclic experiments, shedding light on the evolution patterns of residual strain and hysteresis energy during cyclic loading. It provides insights into the design of reusable and fatigue-resistant diamond-type TPMS structures for various engineering applications.

Crystal structure of nickel orthovanadate (Ni3V2O8) at 299 (3) K and 1323 (8) K: an X-ray diffraction study.

Nickel orthovanadate is a promising material with potential applications in energy storage and photocatalytic devices. The crystal structure of Ni3V2O8 at 299 (3) K and 1323 (8) K was studied using X-ray powder diffraction. The sample was a single-phase orthorhombic kagome-staircase-Ni3(VO4)2-type structure (space group Cmca) at both temperatures. The phase purity and morphology was studied using energy-dispersive X-ray spectroscopy and scanning electron microscopy. The refined unit-cell parameters at 299 (3) K are a = 5.93384 (4) Å, b = 11.38318 (7) Å and c = 8.23818 (5) Å, and at 1323 (8) K are a= 6.02077 (7) Å, b = 11.48838 (7) Å and c = 8.32611 (9) Å. The obtained results indicate thermal expansion anisotropy, with a largest expansivity along a. Variations in Ni-O and V-O bonds with temperature are observed. The variation in the Ni-O bond is about one order higher in magnitude than that of the V-O bond, signifying the high rigidity of V-O bonds. The unit-cell size variations with rising effective ionic volume of the divalent A ion in the A3B2O8 family [A = Ni, Mg, Zn, Co, Mn (experimental data) and also A = Cu, Cd (theoretical data), B = V or As] are analyzed. Based on experimental and theoretical data, trends within the family are observed and the unit-cell size for reported solid solution of nickel (87%) and copper (13%) mixture in (Ni1-xCux)3V2O8 are predicted. Predictions are also provided for some hypothetical A3B2O8 ternary compound and solid solutions.

An Ultra‐Thin Dual‐Polarized Bandpass Frequency Selective Surface for 2.45‐/5.8‐GHz ISM Bands

ABSTRACTThis paper presents the design of a single‐layer, double‐sided frequency selective surface (FSS) with bandpass characteristics at the S‐band (2.45 GHz) and C band (5.8 GHz) for sub‐6‐GHz Industrial Scientific and Medical (ISM) bands. The proposed FSS is based on the concept of complementary FSS that produces additional resonant modes. The FSS is constructed using an ultra‐thin microwave laminate with a thickness of 0.00076λeff calculated at the C‐band. The solid patch on the front side of the FSS unit cell is composed of an octagonal ring connected to four spiral arms while the slotted region on the rear side is complementary to the geometry on the front side. The unit cell size of the proposed FSS element is 0.087λeff × 0.087λeff. The FSS has an ultra‐low profile with at least 40% size reduction compared to the state‐of‐the‐art. The FSS element offers 11.12% (288 MHz) and 11.45% (650 MHz) at 2.45 GHz and 5.8 GHz, respectively, at x‐polarization while 5.8% (142 MHz) and 5.9% (342 MHz) bandwidth in the y‐polarization. The FSS element has a rotational symmetric structure offering enhanced polarization stability and angular independent operation for oblique incidences up to 80°. Furthermore, FSS operation is stable, which is evaluated and presented. The prototype bandpass FSS is fabricated, and the simulation results are validated in real‐time using experiments.

Boosting Energy-Storage in High-Entropy Pb-Free Relaxors Engineered by Local Lattice Distortion.

The high-entropy strategy has shown potential in advancing the energy-storage performance of dielectric capacitors, offering benefits to a range of electronic and electrical systems. However, designing high-performance high-entropy relaxor ferroelectrics (RFEs) presents challenges due to the unclear correlation between their core effects and local polarization heterogeneity. Here, we demonstrate that by engineering the local lattice distortion, a core effect in high-entropy systems, to manipulate the local polarization configuration, a giant energy density (Wrec) of 18.7 J cm-3 and high efficiency (η) of 85% can be achieved in (Bi0.5K0.5)TiO3-based high-entropy bulk RFE ceramics. Atomic-level local structural analysis unveils that the local lattice distortion field can be flattened by introducing ions with less size mismatch. The increase in configurational entropy from 1.54 to 2.06R is associated with a smoother polar displacement vector field and a reduction in the size of polar clusters to several unit-cell sizes with weak coupling. Consequently, a substantial decrease in hysteresis and an enhancement in the breakdown field strength can be obtained, leading to a significant improvement in energy density by over 6 times and efficiency by 3 times. Our research establishes a relationship between local lattice distortion, atomic polar displacement, and energy-storage performance in complex high-entropy systems, providing insights for enhancing energy-storage performance via a local structure design.