Spherical Substrate Research Articles

Resonance energy transfer in the presence of a spherical cavity and dispersive substrate

Resonance energy transfer in the presence of a spherical cavity and dispersive substrate

Design and fabrication of metal spherical conformal thin film multisensor for high-temperature environment

Conformal thin-film sensors enable precise monitoring of the operating conditions of components in extreme environments. However, the development of these sensors encounters major challenges, especially in uniformly applying multiple film layers on complex metallic surfaces and accurately capturing diverse operational parameters. This work reports a multi-sensor design and multi-layer additive manufacturing process targeting spherical metallic substrates. The proposed high-temperature dip-coating and self-leveling fabrication process achieves high-temperature thin-film coatings with excellent uniformity, high-temperature electrical insulation, and adhesion properties. The fabricated Ag/Pt thin film thermocouple arrays and a heat flux sensor exhibit a maximum temperature resistance of up to 960 °C, with thermoelectric potential outputs and high-temperature resistance closely mirroring those of wire-based Ag/Pt thermocouples. Harsh environmental testing was conducted using high-power lasers and a flame gun. The results show that the array of thin-film conformal thermocouples more accurately reflected temperature changes at different points on a spherical surface. The heat flux sensors achieve responses within 95 ms and withstand environments with heat fluxes over 1.2 MW/m2. The proposed multi-sensor design and fabrication method offers promising monitoring applications in harsh environments, including aerospace and nuclear power.

Geometry-induced friction at a soft interface

Soft and biological matter come in a variety of shapes and geometries. When soft surfaces that do not fit into each other due to a mismatch in Gaussian curvatures form an interface, beautiful geometry-induced patterns are known to emerge. In this paper, we study the effect of geometry on the dynamical response of soft surfaces moving relative to each other. Using a simple experimental scheme, we measure friction between a highly bendable thin polymer sheet and a hydrogel substrate. At this soft and low-friction interface, we find a strong dependence of friction on the relative geometry of the two surfaces-a flat sheet experiences significantly larger friction on a spherical substrate than on flat or cylindrical substrate. We show that the stress developed in the sheet due to its geometrically incompatible confinement is responsible for the enhanced friction. This mechanism also leads to a transition in the nature of friction as the sheet radius is increased beyond a critical value. Our finding reveals a hitherto unnoticed mechanism based on an interplay between geometry and elasticity that may influence friction significantly in soft, biological, and nanoscale systems. In particular, it provokes us to reexamine our understanding of phenomena such as the curvature dependence of biological cell mobility.

Mechanism of collision and drainage of liquid droplet around sphere placed within a hollow cylinder

It is attempted earnestly to elucidate the mechanism of collision and drainage of liquid mass around the spherical substrate suspended within the hollow cylinder using Gerris open-source code by employing Volume of Fluid (VOF) methodology. Various influencing parameters, namely, sphere-to-droplet diameter ratio (Ds/Do), Weber number(We), Ohnesorge number (Oh), and Bond number(Bo) are employed to observe the drainage mechanism through the constricted path. The pattern of the interfacial morphology of droplet collision and drainage mechanism is presented using numerical contours. It is important to mention herein that the droplet undergoes several important stages like collision, cap formation, engulfment, drainage, and pinch-off. The passage between the sphere and the cylinder is sufficiently wider at a lower value of Ds/Do due to which the liquid mass is drained out completely without any hindrance. The drainage process becomes considerably faster at a higher We compared to a lower We. In addition, the flow of liquid mass through the passage gets delayed at a greater Oh than a lower Oh assuming a given value of We and Ds/Do. The liquid drop requires less time to pass through the constricted path at lower Bo for a given value of Ds/Do and We. We have also attempted to quantify the drainage of liquid volume passes through the passage, which is denoted as (Q*=Q/Qo). One can notice the increasing pattern of Q/Qo with continuous progress of time stamp for all cases of Ds/Do for a fixed value of We.

Solvethermal synthesis and thermochromic properties of CaF2@VO2-based core-shell structure composites

Vanadium oxide (VO2)-based core-shell structures exhibit unique properties due to their reversible metal–insulator transition (MIT). As a result, numerous applications on the device level have been reported in the literature. However, since VO2 are multivalent compounds, the controllable preparation of VO2 core-shell-based particles is quite challenging. Along these lines, in this work, to overcome these limitations, the growth mechanism of VO2 shells on spherical substrates was systematically investigated. More specifically, the CaF2@VO2 core-shell microspheres were fabricated successfully by applying the solvent/hydrothermal-calcination method for the first time, while the phase evolution and morphological characteristics of the preparation process were studied in detail. From the obtained results, it was demonstrated that the composite particle's morphology and phase structure strongly depend on the activator, solvent, annealing atmosphere, and the annealing temperature. In addition, the infrared transmittance of the prepared CaF2@VO2(M) coating exhibited a decrease of 34.08 % during the metal–semiconductor phase transition in the 4–12 μm wavelength. Compared with the VO2 coatings and the uncoated CaF2/VO2 coatings, the transmittance conversion performance (ΔT) of the CaF2@VO2(M) coating was also increased by 22.62 % and 21.22 %, respectively.

Evaluation of an x-ray multilayer mirror for radiography at sub-1-keV photon energies.

An x-ray multilayer mirror on a spherical substrate designed for near-normal incidence with a photon energy of ∼738eV (F Heα) was procured and tested. This device is intended to be used for in-flight radiography of the shell in inertial confinement fusion experiments with cryogenic targets on the OMEGA laser at the Laboratory for Laser Energetics. Experiments in self-emission on a small (∼10J) laser system showed that the reflectivity of the mirror is high enough to record an image at laser energies as low as 0.1J. A second set of tests in backlighting geometry on a larger (kJ)-scale, short-pulse laser yielded usable radiographs with laser energies as low as 40J with a spatial resolution of ∼10μm.

Dual-mode SERS-ECL biosensor for robust detection of circulating miRNAs based on in-situ synthesized probes

A novel dual-mode biosensor integrating surface-enhanced Raman spectroscopy (SERS) and electrochemiluminescence (ECL) was developed for the reliable detection of acute myocardial infarction (AMI) related circulating miRNAs. The DNA walker nucleic acid amplification technique was employed for signal amplification and facilitated in-situ synthesis of ECL luminescent clusters and SERS probes. The alkynyl-modified silver nanocluster (AgNC) template strand and the azido-modified DNA probe on the electrode were connected through linker release facilitated by the continuous rolling and cutting action of the DNA walker on the spherical substrate. Under Cu+ catalysis, the alkynyl and azide groups at the junction undergo conversion into triazole molecules, which can serve as SERS probes. Subsequently, AgNCs were synthesized using a template method, with SERS signals emitted due to plasma resonance effects of triazole molecules situated between Au nanoparticles and AgNCs. The developed dual-mode analysis platform efficiently minimizes the potential for signal leakage, significantly corrects systematic errors, improves detection accuracy and sensitivity, and facilitates dependable identification of circulating miRNA. The detection of miRNA-133a exhibited a linear relationship within the concentration range of 100 aM to 1 nM, with detection limits of 32 aM and 0.17 fM in ECL and SERS modes, respectively. The SERS-ECL dual-mode detection platform may provide forward-looking ideas for the field of biosensing and clinical analysis.

Film thickness characterization in dual-axis spin coating of a sphere

The versatility of spin coating technology makes it a preferred method for producing the thin film layers used to manufacture products from solar panels and smartphones to sunglasses and CDs. However, the process requires a flat, rigid substrate to produce uniform films, which limits its use to planar devices. A novel multi-axis manipulator has been developed to extend the application of spin coating, enabling controlled thin film deposition onto curved surfaces. Various rotational schemes were studied to link the flow of a liquid film over a curved surface to forces induced by complex rotational dynamics. When the angular velocity exceeds a threshold, centrifugal force dominates the flow, pushing the fluid away from the instantaneous axis of rotation. This produces axisymmetric coating profiles when using consistent single or dual-axis rotation. Areas of near uniformity present around the spin axis poles for single-axis rotation and around the substrate’s equator for dual-axis schemes. Sensitivities between the spherical substrate dynamics and the evolving fluid flow were investigated, exploring the parameters that promoted the production of uniform curved film layers for microfabrication processes. This enabled the evolution of the spin coating technique to effectively form curved polymer coatings with improved thickness control. The presented research outlines the capabilities of a multi-axis spin coating machine when used to coat spherical substrates. Therefore, enabling the use of fluid mechanics models to identify the optimal motion kinematics required to create uniform curved films.

Magnetron sputter deposition of ultrathick boron carbide coatings on spherical substrates for inertial confinement fusion

Most designs of inertial confinement fusion (ICF) targets require ablators in the form of hollow spherical shells with an outer diameter of ∼1−3 mm and a wall thickness of ∼20−200 microns. Vapor deposition onto rolling spherical substrates (templates) is the generally preferred method for the fabrication of ICF ablators. Amorphous boron carbide (B4C) is a promising material for use as an ablator due to its favorable properties. However, the challenge lies in creating ultrathick B4C coatings with submicron-scale density uniformity on rolling spherical substrates. Here, we show examples from our ongoing systematic study of the deposition of B4C onto 2-mm-diameter Si spheres by radio-frequency magnetron sputtering (RFMS). We start with a RFMS recipe developed for depositing planar amorphous B4C films with close-to-zero residual stress and transfer the deposition process from stationary planar substrates to rolling spherical substrates. A major challenge of the deposition onto rolling spheres is preventing the formation of so-called nodular defects, attributed to the incorporation of particulates into the growing film. To address this challenge, we explore ways to minimize the generation and accumulation of particulates on the substrate holder by a combination of enhanced film adhesion to the substrate holder surface and removal of particulates from the holder area where spherical substrates are rolling. With this approach, we demonstrate the deposition of an ∼75-micron-thick B4C coating on a Si sphere.

Experimental-Theoretical Method for Assessing the Stiffness and Adhesion of the Coating on a Spherical Substrate

Experimental-Theoretical Method for Assessing the Stiffness and Adhesion of the Coating on a Spherical Substrate

Adhesion and morphology of mammalian cells on nanoporous and nonporous spherical carbon substrates

Three spherical activated carbons (SACs) were used as substrates for mammalian cell proliferation. SACs were obtained by carbonizing styrene-co-divinylbenzene ion exchangers 35WET, XAD4, or 1200H. The new materials (XAD_C, WET_C, and H_C) were characterized by adsorption–desorption nitrogen isotherms and mercury intrusion porosimetry. XAD_C and WET_C exhibited well-developed BET surface areas, similar total pore volumes, and highly different pore size distributions. H_C was nonporous spherical material—reference material. The XAD_C was meso-macroporous, but the WET_C was micro-mesoporous. All SACs were not cytotoxic toward Leydig TM3 cells. The differences in porous structure and morphology of the carbon scaffolds led to morphological differences in adhered cells. The monolayer of cells was distributed flat over the entire WET_C and H_C surfaces. Leydig TM3 cells adhered to nonporous SAC but were easily washed out due to weak adhesion. The cells adhered in clusters to XAD_C and proliferated in clusters. As microscopic techniques and viability tests demonstrated, only nanoporous carbons provided a good surface for the attachment and proliferation of eukaryotic cells.

Oviposition preference for spherical surfaces is shared among multiple Drosophila species except D. melanogaster (Diptera: Drosophilidae)

AbstractOviposition preference for spherical substrates has been reported in some insects but not in Drosophila species until the recent finding that Drosophila suzukii preferentially lays eggs on spherical surfaces with a smaller radius, whereas D. melanogaster does not. This finding raised two questions: (i) Was this trait specifically acquired in D. suzukii or lost in D. melanogaster? (ii) In the latter case, is it due to the long‐term laboratory culture using oviposition substrates with flat surfaces? To answer these questions, we examined the oviposition preference of three Drosophila species using the stocks recently established from wild individuals. As with D. suzukii, D. simulans and D. takahashii showed significant preference for spherical surfaces with a smaller radius, suggesting that this trait is shared by multiple Drosophila species. In contrast, D. melanogaster did not show any preference for either smaller or larger radii, showing that the preference already has been lost in the natural population of D. melanogaster. It may be possible that the loss of oviposition preference for spherical surfaces is involved in the evolutionary process of D. melanogaster becoming a human commensal.

Fabrication of Hyperbranched Photomechanical Crystals Composed of a Photochromic Diarylethene.

We report the fabrication of hyperbranched hollow crystals of 1,2-bis(2,5-dimethyl-3-thienyl)perfluorocyclopentene on a concave surface of the spherical glass substrate by sublimation and their practical photomechanical behaviors. The number of units of the branched structure of the hollow crystals composed of this compound is proportional to the substrate curvature of the substrate. Compared with the sublimation process of the same compound on the flat glass substrate, two kinds of the thin film domains are generated separately in the center and around the edge of the spherical glass substrate. Especially under the high relative humidity condition, the boundaries between these thin film domains move gradually around the edge through the center during as long as 6 h of sublimation time so that the hyperbranched hollow crystals are densely produced on the entire surface of the substrate. These hyperbranched hollow crystals can be prepared with the highly ordered molecular packing due to the very slow formation process of the crystalline walls of the hollow structures. Furthermore, the photo-induced bending behaviors in the few- and highly-branched hollow crystals have the practical roles in moving and bending the minute objects according to their characteristics of these branched shapes.

Magnetic MOF Substrates for the Rapid and Sensitive Surface-Enhanced Raman Scattering Detection of Uranyl.

With the widespread use of uranium in the nuclear industry, achieving rapid and sensitive detection of uranium contaminants is critical for reducing environmental pollution. Surface-enhanced Raman scattering (SERS), with its high sensitivity and unique fingerprint properties, has been used for the analysis of uranyl. However, the weak affinity of Au for uranyl remains a challenge in the development of spherical Au-based SERS substrates. The metal-organic framework (MOF) material ZIF-8 exhibits excellent adsorption capacity for uranyl and could overcome this limitation. In this study, ZIF-8 porous structures were modified on a magnetic SERS substrate, Fe3O4@SiO2@Au (FA), for the rapid and sensitive detection and analysis of the uranyl species. Uranyl was adsorbed by ZIF-8, allowing ready access to the hot spots in the interstices of Au nanoparticles (AuNPs). Symmetrically stretched vibrating bonds of O═U═O were detected at 829 cm-1 as the characteristic peak of uranyl by surface plasmon resonance between the AuNPs. The ZIF-8 coating had minimal influence on target detection as the detection limit for 4-MPY was only half an order of magnitude lower than before modification. The enhancement factor for uranyl reached 106. The substrate showed excellent sensing performance in a neutral or alkaline environment. It was used to detect uranyl in tap water and river water; rapid separation of the species from the water samples was achieved using an external magnet to extract radioactive waste. The proposed substrate offers a route for monitoring and detecting uranyl contamination and an approach for achieving rapid on-site detection, providing a promising application for environmental contaminant detection.

Geomorphometry and microelectronic metrology: Converged realms

AbstractThis article discusses the application of geomorphometric methods in microelectronic metrology. Six typical microelectronic items were geomorphometrically analyzed using their digital elevation models with nano‐ and micrometer‐range resolution and elevation difference: (1) a silicon–quartz structure; (2) a mechanically polished silicon wafer; (3) a photovoltaic blend sample; (4) an X‐ray optical element (a fused quartz spherical concave substrate); (5) a Bosch process‐formed, 20 aluminum layered membrane; and (6) a silicon–glass assembly with a volumetric defect. Geomorphometric modeling increases significantly the visibility and informativeness of data presentation, allowing to identify effectively the spatial distribution of nano‐ and microforms of the surface of microelectronic items. Geomorphometric methods provide an opportunity to study the size, location, and characteristic features of nano‐ and microtopographic inhomogeneities of microelectronic items using maps of minimum, maximum, mean, and unsphericity curvatures as well as other morphometric variables.

In-situ confined growth of defective MIL-100(Fe) in macroporous polyacrylate spherical substrate at room temperature for high-efficient toluene removal

The hazard caused by toluene has attracted worldwide attention, and it is of practical significance to study the efficient adsorption of toluene for environmental governance. In this work, a hierarchical metal–organic framework (MOF), MIL-100(Fe), was crystallized on the surface of a macroporous polyacrylate (PAA) spherical substrate at room temperature through an in-situ confinement growth strategy to form MIL-100(Fe)@PAA composite. By decreasing the nucleation energy barrier, the average size of MIL-100(Fe) crystals was reduced from 400 nm to 55 nm and defects as adsorption sites for toluene were able to install in the crystal lattices. Therefore, the composite provided excellent static and dynamic adsorption properties for toluene, much better than the pristine MIL-100(Fe). The potential mechanism for crystal defects to significantly improve the adsorption performance was subsequently explored through kinetic fitting and density functional theory (DFT) calculation. All results indicated that the innovative MIL-100(Fe)@PAA prepared using defect engineering and effective molding technology was potent in both toluene removal and regeneration, which was expected to provide a new avenue for the facile synthesis of molded MOF composites.

A Versatile Extended Stöber Approach to Monodisperse Sub-40nm Carbon Nanospheres for Stabilizing Atomically Dispersed Fe─N4 Sites Toward Efficient Oxygen Reduction Electrocatalysis.

The development of atomically dispersed iron-nitrogen-carbon (Fe─N─C) catalysts as an alternative to precious platinum holds great potential for the substantial progress of a variety of oxygen reduction reaction (ORR)-associated energy conversion technologies. Nevertheless, the precise synthesis of Fe─N─C single atomic catalysts (SACs) with a high density of accessible active sites and pronounced electrocatalytic performance still remains an enormous challenge. Herein, an innovative extended Stöber method is designed for the controllable preparation of monodisperse small-sized N-doped carbon colloidal nanospheres (≈40nm) anchoring atomically isolated Fe─N4 sites (abbreviated as Fe-SA@N-CNSs hereafter) with a narrow size distribution and high uniformity. Benefiting from the single Fe─N4 moieties and the unique spherical carbon substrate, the resultant Fe-SA@N-CNSs exhibit excellent ORR activity, outstanding long-term durability, and methanol tolerance in KOH electrolyte. More impressively, when further assembled into a flexible solid-state rechargeable zinc-air battery (ZAB), the Fe-SA@N-CNSs-driven ZAB delivers a higher open circuit voltage, a larger power density, and robust cycling/mechanical stability, outperforming the state-of-the-art Pt/C-based counterpart and further testifying the great potential of the as-prepared Fe-SA@N-CNSs in diverse ORR-related practical energy devices. The developed extended Stöber method provides an efficient and versatile avenue toward the preparation of a series of well-defined SACs for diverse electrocatalytic systems.

Influence of the Deposition Parameters on the Properties of TiO2 Thin Films on Spherical Substrates.

Wastewater treatment targeting reuse may limit water scarcity. Photocatalysis is an advanced oxidation process that may be employed in the removal of traces of organic pollutants, where the material choice is important. Titanium dioxide (TiO2) is a highly efficient photocatalyst with good aqueous stability. TiO2 powder has a high surface area, thus allowing good pollutant adsorption, but it is difficult to filter for reuse. Thin films have a significantly lower surface area but are easier to regenerate and reuse. In this paper, we report on obtaining sol-gel TiO2 thin films on spherical beads (2 mm diameter) with high surface area and easy recovery from wastewater. The complex influence of the substrate morphology (etched up to 48 h in concentrated H2SO4), of the sol dilution with ethanol (1:0 or 1:1), and the number of layers (1 or 2) on the structure, morphology, chemical composition, and photocatalytic performance of the TiO2 thin films is investigated. Etching the substrate for 2 h in H2SO4 leads to uniform, smooth surfaces on which crystalline, homogeneous TiO2 thin films are grown. Films deposited using an undiluted sol are stable in water, with some surface reorganization of the TiO2 aggregates occurring, while the films obtained using diluted sol are partially washed out. By increasing the film thickness through the deposition of a second layer, the roughness increases (from ~50 nm to ~100 nm), but this increase is not high enough to promote higher adsorption or overall photocatalytic efficiency in methylene blue photodegradation (both about 40% after 8 h of UV-Vis irradiation at 55 W/m2). The most promising thin film, deposited on spherical bead substrates (etched for 2 h in H2SO4) using the undiluted sol, with one layer, is highly crystalline, uniform, water-stable, and proves to have good photocatalytic activity.

Fabrication of hyperbranched polyamidoamine immobilized mesocellular siliceous foam for rapid decontamination of lead(II) from aqueous solution

Developing of adsorbents with merits of higher adsorption capacity and quicker adsorption equilibrium through facile method merits more attention. Generally, large specific surface area porous adsorbent coupled with multi functional groups is a wise option. In the current work, a feasible protocol of preparing efficient adsorbent toward Pb2+ was established via integrating amino abundant hyperbranched polyamidoamine and bimodal pore structured mesocellular siliceous foam. The polyamidoamine was synthesized through a vacuum thermo polymerization method by gradually elevating temperature. The uniform spherical mesocellular siliceous foam substrate was prepared via inorganic salt-assisted soft-template method, and the pore structure and particle morphology were adjusted through post hydrothermal treatment. The obtained hyperbranched polyamidoamine immobilized mesocellular siliceous foam was characterized using FT-IR, SAXS, BET, SEM, TEM, TGA and zeta potential measurement techniques. Large specific surface area, unique bimodal pore structure with interconnected spherical and window pore and ultra large pore diameter rendered the adsorbent high adsorption capacity and efficient elimination. Batch experiment results elucidated that various operating parameters including pH, contact time, initial Pb2+ concentration, temperature and ionic strength deemed to be at play in adsorption behavior. The measured experimental maximum adsorption capacity at 298.15 K was 142.87 mg·g−1. The equilibrium data fitted well by pseudo second order kinetic model unveiled that the rate determining step might be chemical adsorption. The adsorption behavior was found to more suitable described with Langmuir isotherm model, implying the formation of adsorbate monolayer, and thus a maximum adsorption capacity of 315.46 mg·g−1 at 298.15 K was estimated. An underlying spontaneous entropy increased endothermic nature of adsorption of Pb2+ by the as-prepared adsorbent was conceived through adsorption thermodynamics study. Furthermore, a possible adsorption mechanism of comprehensive interaction of chemical chelation and ion exchange was proposed. This study supports the prospect that hyperbranched polyamidoamine immobilized mesocellular siliceous foam can serve as a candidate for efficiently removing Pb2+ from aqueous solution.

Preparation of Micron-Sized TS-1 Spherical Membrane Catalysts and Their Performance in the Epoxidation of Chloropropene.

Titanium silica (TS-1) membrane catalysts grown on the surfaces of spherical substrates can both exploit the high catalytic performance and facilitate their separation from products after the reaction. In this work, a simple static crystallization method was used to perform the in situ construction of a TS-1 membrane on the surfaces of micron-sized spherical carriers. The shortcomings of the TS-1 membrane under static crystallization conditions were overcome by in situ dynamic crystallization, and the effect of rotation speed on the formation of the molecular sieve membrane was investigated. The results showed that the molecular sieve membrane was smooth and homogeneous, with a higher synthesis efficiency at a slow rotational speed. The micron TS-1 spherical membrane catalytic chloropropene epoxidation reaction was investigated in a fixed bed, and the conversion of hydrogen peroxide and selectivity of epichlorohydrin reached 99.4 and 96.8%, respectively. After being reused twice, the catalyst still maintained a stable catalytic performance.