Geometrical Morphologies Research Articles

Heat transfer enhancement characteristics of sinusoidal corrugated tubes fabricated via laser powder bed fusion

Laser powder bed fusion (LPBF) has emerged as a powerful tool to develop heat transfer devices with higher efficiency. Corrugated tubes are commonly used components to achieve enhanced heat transfer in these devices. However, there still lacks a comprehensive study on the thermal-hydraulic performance of LPBF-fabricated corrugated tubes. In this work, we investigated the heat transfer enhancement characteristics of sinusoidal corrugated tubes (SCTs) fabricated via LPBF. SCTs with different amplitude-to-diameter ratios (A/D ratio) and wavelength-to-diameter ratios (S/D ratio) were designed and fabricated. The geometrical morphologies and surface roughness of LPBF-fabricated SCTs were characterized. Numerical simulations were performed to investigate the effects of A/D ratio and S/D ratio on the flow patterns and flow dynamics. A test system was developed to measure the pressure loss and thermal performance. Performance Evaluation Criterion were calculated to characterize the heat transfer enhancement. A/D ratio was found to have more significant impacts on the friction factor and Nusselt numbers than S/D ratio. Correlation models were developed to predict friction factors and Nusselt numbers based on the least square method. Mean prediction errors of ±3.3 % and ±5.3 % and maximum prediction errors of ±11.6 % and ±18.1 % were achieved for Nusselt numbers and friction factor, respectively.

Additive manufacturing multiscale ultrahigh strength and high accuracy nanocrystalline nickel structures and components using ultrafine anode scanning through-mask electrodeposition

Through-mask electrodeposition (TM-ECD) is a widely-used technique for manufacturing mesoscale and microscale precision metal features and components in a mass-production manner. However, in most cases, the traditional TM-ECD processes are very hard to fabricate high-accuracy multiscale (macroscale, mesoscale, microscale) features simultaneously due to the inherent nonuniform distribution of the applied energy fields including electric field, mass transportation field, and temperature field during electrodeposition. Furthermore, nanocrystalline microstructures have not been realized by TM-ECD without additional nonmetallic additives or mechanical stirring. Here, a ultrafine anode scanning through-mask electrodeposition (UASTM-ECD) process operated at DC mode is developed to further trigger the formation of nanocrystalline without additives, in which a ultrafine wire-shaped inert anode embedded in a stirring paddle reciprocates over the top surfaces of the through-masks with a spacing of less than 100 μm. Experimental investigations into this unique TM-ECD were systemically carried out by examining the geometrical profile, surface morphologies, forming accuracy, grain size, and mechanical properties of the fabricated nanocrystalline structures and components. Our findings showed that the UASTM-ECD can facilitate to achieve a significantly improved thickness distribution uniformity and considerably fine nanocrystalline ultrapure microscale and mesoscale complex cross-sectional arrays components over the traditional TM-ECD processes even though the multiscale features and components are simultaneously deposited on the same substrate. These result from the unique deposition manner of the UASTM-ECD in which the metal materials are intermittently filled into the patterned photoresist cavity molds very locally and at the extremely high current densities. This versatile approach eliminates the possible contamination by additives and integration difficulty of mechanical stirring, which can be used to fabricate the multiscale ultrahigh strength and high accuracy ultrapure nanostructured-material features.

Recent Advances in 1D Photonic Crystals: Diverse Morphologies and Distinctive Structural Colors for Multifaceted Applications

Abstract1D photonic crystals (1DPCs) with hierarchically structured lamellar periodic frameworks that enable precise control of light‐matter interactions and contribute robust structural colors represent a groundbreaking advancement in optical materials. The microstructural characteristics and the constituent material properties of these photonic materials play pivotal roles in determining their optical performance and functionality. In recent years, a diverse array of novel 1D photonic structures crafted from various materials emerged, showcasing their tremendous potential in advanced applications. This article provides an in‐depth review of the recent developments in 1DPCs, emphasizing their morphological designs, fabrication strategies, and optical applications. In detail, 1DPCs featuring distinct geometrical morphologies, including lamellar, helical, fibrous, spherical, and nanochained structures are systematically introduced, highlighting the unique optical properties arising from their periodic microstructures. Then, various fabrication methods, involving some innovative techniques utilizing standing‐wave optics, UV dual photopolymerization, and inkjet printing, are succinctly summarized for constructing different photonic structures by using diverse building materials. Subsequently, some typical application examples of 1D photonic materials are listed and discussed involving visual sensing, intelligent displays, anti‐counterfeiting technology, photonic pigments, and optical devices. Finally, the passage addresses the current challenges and presents a forward‐looking perspective on the future fabrication and application of 1DPCs.

Single-Molecule Morphology of Topologically Digested Olympic Networks

The kinetoplast DNA (kDNA) is the archetype of a two-dimensional Olympic network, composed of thousands of DNA minicircles and found in the mitochondrion of certain parasites. The evolution, replication, and self-assembly of this structure are fascinating open questions in biology that can also inform us how to realize synthetic Olympic networks . To obtain a deeper understanding of the structure and assembly of kDNA networks, we sequenced the kDNA genome and performed high-resolution atomic force microscopy and analysis of kDNA networks that had been partially digested by selected restriction enzymes. We discovered that these topological perturbations lead to networks with significantly different geometrical features and morphologies with respect to the unperturbed kDNA, and that these changes are strongly dependent on the class of DNA circles targeted by the restriction enzymes. Specifically, cleaving maxicircles leads to a dramatic reduction in network size once adsorbed onto the surface, while cleaving both maxicircles and a minor class of minicircles yields noncircular and deformed structures. We argue that our results are a consequence of a precise positioning of the maxicircles at the boundary of the network, and we discuss our findings in the context of kDNA biogenesis, design of artificial Olympic networks, and detection of perturbations. Published by the American Physical Society 2024

From core@shell ZnSe/FeSe2@MoSe2 to core@shell@shell magnetic ZnFe2O4@C@MoSe2 flower-like nanocomposites: An effective strategy to boost microwave absorption performance of MoSe2-based nanocomposites

The selenylation/sulfuration of magnetic precursor brings about the great challenges to construct magnetic transition metal dichalcogenides (TMDs)-based multicomponent nanocomposites (MCNCs), which greatly hinders the improvements in magnetic loss ability and impedance matching characteristic. Theoretically speaking, the addition of carbon layer is conducive to protect the magnetic nanoparticles, optimize the impedance matching, strengthen the interfacial polarization and magnetic loss abilities, and so on. In order to verify these ideas, herein, we elaborately designed and produced core@shell ZnSe/FeSe2@MoSe2 and core@shell@shell ZnFe2O4@C@MoSe2 flower-like MCNCs. The results of comparative study indicated that the as-prepared ZnSe/FeSe2@MoSe2 and ZnFe2O4@C@MoSe2 with the different MoSe2 contents and flower-like geometrical morphologies could be synthesized by regulating the amounts of Mo and Se sources. And the introduction of carbon layer not only effectively inhibited the selenylation of ZnFe2O4 precursor, but also greatly improved the impedance matching characteristic, dielectric and magnetic loss capabilities. The obtained ZnFe2O4@C@MoSe2 MCNCs presented the excellent comprehensive microwave absorption properties (MAPs) including strong absorption capability, broad frequency bandwidth and thin matching thickness. Therefore, our findings not only presented a simple and viable route to produce magnetic TMDs-based MCNCs, but also provided an effective strategy to boost their comprehensive MAPs.

Indirect 3D Bioprinting of a Robust Trilobular Hepatic Construct with Decellularized Liver Matrix Hydrogel.

The liver exhibits complex geometrical morphologies of hepatic cells arranged in a hexagonal lobule with an extracellular matrix (ECM) organized in a specific pattern on a multi-scale level. Previous studies have utilized 3D bioprinting and microfluidic perfusion systems with various biomaterials to develop lobule-like constructs. However, they all lack anatomical relevance with weak control over the size and shape of the fabricated structures. Moreover, most biomaterials lack liver-specific ECM components partially or entirely, which might limit their biomimetic mechanical properties and biological functions. Here, we report 3D bioprinting of a sacrificial PVA framework to impart its trilobular hepatic structure to the decellularized liver extracellular matrix (dLM) hydrogel with polyethylene glycol-based crosslinker and tyrosinase to fabricate a robust multi-scale 3D liver construct. The 3D trilobular construct exhibits higher crosslinking, viscosity (182.7 ± 1.6 Pa·s), and storage modulus (2554 ± 82.1 Pa) than non-crosslinked dLM. The co-culture of HepG2 liver cells and NIH 3T3 fibroblast cells exhibited the influence of fibroblasts on liver-specific activity over time (7 days) to show higher viability (90-91.5%), albumin secretion, and increasing activity of four liver-specific genes as compared to the HepG2 monoculture. This technique offers high lumen patency for the perfusion of media to fabricate a densely populated scaled-up liver model, which can also be extended to other tissue types with different biomaterials and multiple cells to support the creation of a large functional complex tissue.

Mechanical and fluid characteristics of triply periodic minimal surface bone scaffolds under various functionally graded strategies

Abstract A laser powder bed fusion additive manufacturing has enabled the fabrication of triply periodic minimal surface (TPMS). These structures are widely acknowledged for their suitability in bone implant applications. Nevertheless, although it is essential for TPMS-based implants to exhibit graded features to mimic those of natural bones for desirable functionality, the effect of graded features on mechanical properties, flow behavior, and geometrical morphologies requires further clarification. As a result, this study carried out a comprehensive numerical and experimental assessment on the impact of graded IWP structures on the effective elastic modulus, Gaussian curvature, permeability, and fluid-induced wall shear stress. Among various TPMS architectures, the IWP structure was chosen to be explored in this work owing to its favorable physical responses for bone tissue ingrowth as reported in the literature. Overall, we found that the grading features had a considerable impact on the global response such as the effective modulus and fluid permeability. However, the local response such as Gaussian curvatures and fluid-induced wall shear stress was significantly less affected.

Magnetic modulation of core@shell MoS2-based flower-like multicomponent nanocomposites to improve microwave attenuation

Nanocomposites with a three-dimensional (3D) flower-like geometrical morphology were considered as excellent microwave absorbers (MAs) because of the numerous effective sites for the multiple reflections of electromagnetic (EM) wave. Herein, for optimizing the EM matching characteristic and taking full advantage of interface polarization, a strategy of magnetic modulation was proposed to further improve the EM wave absorption performances (EMWAPs) of MoS2-based nanocomposites. We adopted a simple hydrothermal route and a combined method of hydrothermal treatment/hydrogen reduction to synthesize core@shell CoFe2O4@MoS2 and CoFe@MoO2/MoS2 flower-like nanocomposites, respectively. The obtained results indicated that the hydrogen reduction effectively improved their magnetic properties and magnetic loss capabilities, and their 3D flower-like geometrical morphologies were well maintained during the hydrogen reduction process. The obtained core@shell CoFe@MoO2/MoS2 flower-like nanocomposites presented the extraordinary comprehensive EMWAPs including the optimal reflection loss value of −54.83 dB with the matching thicknesses (dm) value of 2.05 mm and effective absorption bandwidth value of 6.40 GHz with the dm value of 2.59 mm, which were evidently superior to the properties of CoFe2O4@MoS2. Therefore, the findings provided an effective pathway to further improve EMWAPs of MoS2-based core@shell nanocomposites and the as-prepared core@shell CoFe@MoO2/MoS2 flower-like nanocomposites could be utilized as the novel high-efficient MAs.

In Situ Liquid Cell Transmission Electron Microscopy Investigation on the Dissolution-Regrowth Mechanism Dominating the Shape Evolution of Silver Nanoplates

Uniform silver nanostructures with specific geometrical morphologies, such as triangular and hexagonal nanoplates, often exhibit unique physicochemical properties with various potential application...

Experimental Study on Thermal Conductivity and Rectification in Suspended Monolayer MoS2.

Thermal rectification is an attractive phenomenon for thermal management, which refers to a specific behavior in a heat transfer system where heat flow in one direction is stronger than that in the opposite direction under the same conditions. Two-dimensional monolayer molybdenum disulfide (MoS2) synthesized by chemical vapor deposition (CVD) has exhibited exceptional thermal, optical, and electrical properties due to its special structure; however, the thermal rectification in monolayer MoS2 is still not achieved by experimental measurement. Here, we successfully transferred monolayer MoS2 samples with three geometrical morphologies to the suspended microelectrodes by the PMMA approach. Through further heating the suspended microelectrodes with AC power in the opposite directions of these three monolayer MoS2 samples, we experimentally measured the thermal conductivity and first obtained the thermal rectification of monolayer MoS2. The rectification coefficients of monolayer MoS2 with three different geometrical morphologies are 10-13, 11-4, and 69-70%. Moreover, a theoretical model was also applied to discuss the dependence of thermal rectification on the geometrical asymmetry (angle and spacing). The results demonstrate that the monolayer MoS2 has an obvious thermal rectification phenomenon owing to the asymmetric structure, and it would have great potentials in the application of thermal energy control and management.

Examination of mullite ceramic specimens made by conventional casting method from kaolin and sawdust

Using relatively low-cost raw materials (conventional kaolin and sawdust powders) and simple technology, the authors have developed new ceramic composite materials which can successfully meet different industrial requirements. Casting masses (slurries) were made by mixing and milling different compositions of the powders with distilled water. The ceramic specimens were made by conventional gravitation slipcasting method, after drying of the green specimens, the samples were sintered in an electric kiln under oxidation and reduction atmosphere at 1250°C. The prepared and sintered specimens were tested based on geometrical sizes, microstructures and morphologies using scanning electron microscopy. In this work, the authors present some parts of the results of their research and investigation.

Advances in metal-organic framework coatings: versatile synthesis and broad applications.

Metal-organic frameworks (MOFs) as a new kind of porous crystalline materials have attracted much interest in many applications due to their high porosity, diverse structures, and controllable chemical structures. However, the specific geometrical morphologies, limited functions and unsatisfactory performances of pure MOFs hinder their further applications. In recent years, an efficient approach to synthesize new composites to overcome the above issues has been achieved, by integrating MOF coatings with other functional materials, which have synergistic advantages in many potential applications, including batteries, supercapacitors, catalysis, gas storage and separation, sensors, drug delivery/cytoprotection and so on. Nevertheless, the systemic synthesis strategies and the relationships between their structures and application performances have not been reviewed comprehensively yet. This review emphasizes the recent advances in versatile synthesis strategies and broad applications of MOF coatings. A comprehensive discussion of the fundamental chemistry, classifications and functions of MOF coatings is provided first. Next, by modulating the different states (e.g. solid, liquid, and gas) of metal ion sources and organic ligands, the synthesis methods for MOF coatings on functional materials are systematically summarized. Then, many potential applications of MOF coatings are highlighted and their structure-property correlations are discussed. Finally, the opportunities and challenges for the future research of MOF coatings are proposed. This review on the deep understanding of MOF coatings will bring better directions into the rational design of high-performance MOF-based materials and open up new opportunities for MOF applications.

Laser Induced Nano and Micro Structures of Molybdenum Surface Applied in Multistage Depressed Collector for Secondary Electron Suppression

The laser processing molybdenum metal surface method was first proposed to enhance the efficiency of multistage depressed collectors (MDCs). In this study, the secondary electron yield (SEY), surface geometrical morphologies and chemical states of laser processed Mo metal samples were characterized. For the first time, the effects of laser parameters and incident angle of primary electrons on the SEY property of laser induced nano and micro structures of molybdenum surface were investigated. The influence rule of laser processing patterns, power, pitch spacing, scanning speed on surface morphologies and SEY were systematically explored. A maximum SEY of laser processed Mo metal less than one was achieved. The Mo 3d and O 1s core level spectra of Mo metal before and after laser processing were analyzed in this study. Furthermore, the corresponding oxidation states of Mo as well as the relative distribution were elucidated.

Microstructural investigation of different nanopore types in marine-continental transitional shales: Examples from the Longtan formation in Southern Sichuan Basin, south China

Variations in pore types, the complexity of pore structures, and strong heterogeneity complicate the thorough characterization of pore networks in marine–continental shales. In this study, a novel 2D image processing method was proposed, expounded, and verified to clarify the geometrical morphologies, formation mechanisms, the size distributions, proportions and the fractal characteristics of different types of pores in marine–continental shales. Six types of pores (inter-particle, intra-particle, organic matter (OM), inter-crystalline, dissolved pores, and micro-fractures) were classified and morphologically characterized. The different types of shale pores had distinct relatively restricted morphologies, formation mechanisms, and size ranges. Nano- and micron-sized pores were controlled by OM pores and micro-fractures, with the size ranging of 6–80 nm and 200–350 nm and 6–10 μm, respectively. Furthermore, the fractal dimension characteristics were investigated on the basis of the 2D binary images, and the results were verified by the fractal findings obtained from the N2 adsorption data. These fracture dimension results demonstrated that the Longtan shale pore structures had strong complexity and heterogeneity, which was strongly and positively controlled by micro-fractures, inter-crystalline and OM pores. In addition, the total organic carbon content strongly and positively influences the development and anisotropy of the nanoscopic pores, which were dominated by OM pores; while the clay minerals content has a minor effect on the total pore development and heterogeneity of shales but a significant effect on the dissolved pore development of shales, whereas brittle minerals inhibit total pore development and heterogeneity of shales but contribute greatly to the development of the inter-crystalline pores.

Geometrical Morphology of Inkjet-Printed Finger Electrodes on Untreated Multi-Crystalline Silicon Solar Cells

The geometrical morphologies fabricated by continuous and interlacing printing modes on untreated multi-crystalline solar cells are quantitively explored for uniform and high aspect-ratio finger electrodes. The voltage waveform of printhead is well modulated by in-house developed inkjet prototype printer for optimizing the droplet volume and velocity. As the fingers are fabricated with continuous printing mode by varying printing parameters, the bulging and coffee ring morphologies could not be eliminated resulting from the rough and anisotropic features. The interlacing printing mode is first introduced for finger electrodes fabrication. Results show that the width of the printed finger is not influenced by the printing layers and maintains the stable values of ∼60 μ m with pre-heating temperature 80 °C. Moreover, the interlacing printing mode has a high tolerance of droplet spacing variance (30–45 μ m) and suppresses the coffee ring morphology which obtains uniform finger electrodes. The study not only offers good guidance of finger electrodes fabrication for multi-crystalline solar cell manufacturing, but also proposes in-depth insights for the three-dimensional circuit structures fabrication of the emerging printed electronics.

Thermal conductivity and tortuosity of porous composites considering percolation of porous network: From spherical to polyhedral pores

Understanding the effect of percolation behavior of complex geometrical pores on the tortuosity and thermal conductivity of porous composites is very crucial to the design and optimization of porous composites. In this work, we adopt the continuum percolation theory to accurately determine the nonlinear thermal conductivity and tortuosity of porous composites composed of homogeneous solid matrix and three-dimensional pores of geometrical morphologies from the isotropic sphere to anisotropic polyhedra. Through extensive Monte Carlo simulations and the finite-size scaling analysis, the percolation threshold of spherical and polyhedral pores is obtained. Two continuum percolation-based models are respectively presented to derive the tortuosity and thermal conductivity of porous composites over the whole porosities range, including near the percolation threshold. Comparison with extensive experimental, numerical and theoretical results confirms that the present models are capable of accurately determining the percolation threshold and tortuosity of complex geometrical porous networks and the effective thermal conductivity of porous composites as conductor-superconductor and insulator-conductor media. Furthermore, we use the proposed models to probe the influences of pore shape and porosity on the tortuosity and thermal conductivity of porous composites. The results elucidate the intrinsic interplay of component, structure, and thermal conductivity of porous composites, which can provide sound guidance for porous composite design and evaluation.

Experimental comparison of the flow rate and cooling performance of internal cooling channels fabricated via selective laser melting and conventional drilling process

Injection molds with conformal cooling channels have been deemed increasingly important in the mold manufacturing industry. Selective laser melting (SLM) has proven to be an effective process to fabricate conformal cooling molds. However, the surface quality and morphologies of SLM-fabricated cooling channels are different from that of conventional drilled channels. To investigate the differences in the coolant flow rate and cooling performance between SLM-fabricated and drilled cooling channels, test molds with cooling channel diameters of φ2 mm, φ3 mm, and φ4 mm were fabricated via SLM and the computer numerical control (CNC) process. A test system was designed and set up to investigate the flow rate and cooling performance of two types of test molds. The geometrical shape, dimensional accuracy, and surface morphologies of the SLM-fabricated cooling channels were characterized using optical microscopy and laser microscopy. The results indicated that the SLM-fabricated cooling channel exhibited an elliptic shape due to the lack of support along the building direction. The flow rate of the SLM-fabricated cooling channels was smaller than that of the drilled channels due to the low dimensional accuracy and roughness surface. The cooling performance of the SLM-fabricated cooling channels was also poorer than that of the drilled channels due to the presence of unmolten particles and a loose layer on the SLM-fabricated surface. Theoretical analysis was conducted on the influence of surface roughness on the flow rate and cooling performance of two types of channels and the friction factor; Nusselt number and heat transfer coefficient were obtained.

Mechanical response of spiral interconnect arrays for highly stretchable electronics

A spiral interconnect array is a commonly used architecture for stretchable electronics, which accommodates large deformations during stretching. Here, we show the effect of different geometrical morphologies on the deformation behavior of the spiral island network. We use numerical modeling to calculate the stresses and strains in the spiral interconnects under the prescribed displacement of 1000 μm. Our result shows that spiral arm elongation depends on the angular position of that particular spiral in the array. We also introduce the concept of a unit-cell, which fairly replicates the deformation mechanism for full complex hexagon, diamond, and square shaped arrays. The spiral interconnects which are axially connected between displaced and fixed islands attain higher stretchability and thus experience the maximum deformations. We perform tensile testing of 3D printed replica and find that experimental observations corroborate with theoretical study.

Varied crystalline orientation of anatase TiO2 nanotubes from [101] to [001] promoted by TiF6 2− ions and their enhanced photoelectrochemical performance

Herein, we report an ionic cross-linkage process of synthesizing [001] preferred oriented anatase TiO2 nanowires and nanotubes hybrid structure (TWTs) based on anodization method wherein varied amounts of TiF6 2− ions are added in synthetic process. We show how the TiF6 2− ions switch the growth direction of TWTs from [101] to [001] (denoted as T101WTs and T001WTs, respectively) and change their geometrical morphologies, i.e., small ionic radii TiF6 2− ions migrate and partly replace the TiO6 2− octahedra under electric field, which separate out and leave vacancies during annealing process, resulting in a reconstruction of TiO2. Importantly, absorption property and photoelectrochemical (PEC) performance of T001WTs exceed those of T101WTs. Furthermore, CdS QDs are assembled onto TWTs photoelectrodes by successive ionic layer adsorption and reaction technique. Likewise, T001WT/CdS presents superior absorption capability and enhanced PEC performance to those of T101WT/CdS. This could be attributed to their preponderances of improved light absorption capability and decreased electron recombination.

Different optical properties in different periodic slot cavity geometrical morphologies**Project supported by the National Natural Science Foundation of China (Grant No. 61178044), the Natural Science Foundation of Jiangsu Province, China (Grant No. BK20160969), and the University Postgraduate Research and Innovation Project of Jiangsu Province, China (Grant No. KYLX_0723).

In this paper, optical properties of two-dimensional periodic annular slot cavity arrays in hexagonal close-packing on a silica substrate are theoretically characterized by finite difference time domain (FDTD) simulation method. By simulating reflectance spectra, electric field distribution, and charge distribution, we confirm that multiple cylindrical surface plasmon resonances can be excited in annular inclined slot cavities by linearly polarized light, in which the four reflectance dips are attributed to Fabry–Perot cavity resonances in the coaxial cavity. A coaxial waveguide mode TE11 will exist in these annular cavities, and the wavelengths of these reflectance dips are effectively tailored by changing the geometrical pattern of slot cavity and the dielectric materials filled in the cavities. These resonant wavelengths are localized in annular cavities with large electric field enhancement and dissipate gradually due to metal loss. The formation of an absorption peak can be explained from the aspect of phase matching conditions. We observed that the proposed structure can be tuned over the broad spectral range of 600–4000 nm by changing the outer and inner radii of the annular gaps, gap surface topography. Meanwhile, different lengths of the cavity may cause the shift of resonance dips. Also, we study the field enhancement at different vertical locations of the slit. In addition, dielectric materials filling in the annular gaps will result in a shift of the resonance wavelengths, which make the annular cavities good candidates for refractive index sensors. The refractive index sensitivity of annular cavities can also be tuned by the geometry size and the media around the cavity. Annular cavities with novel applications can be implied as surface enhanced Raman spectra substrates, refractive index sensors, nano-lasers, and optical trappers.