Planar Layer Research Articles

The well-defined three-dimensional matrix of a micro-sized silicon/carbon composite promoting lithium-ion transportation.

Micro-sized silicon is a promising anode material due to its high theoretical capacity and low cost. However, its bulk particle size poses a challenge during electrochemical cycling, and the long ion/electron transport paths within it limit the rate capability. Herein, we propose a structural engineering approach for establishing a well-defined three-dimensional (3D) micro-sized silicon/carbon matrix to achieve efficient omnidirectional ionic and electronic conductivity within micro-sized silicon and effectively mitigate the volume changes. The prepared materials, comprising ordered two-dimensional porous silicon nanosheets, offer direct two-dimensional electrolyte transport channels aligned parallel to the layer plane and porous channels oriented perpendicular to the layer plane. These well-defined omnidirectional pathways enable more efficient electrolyte mass transport than the disordered paths within the traditional 3D porous silicon anodes. A robust carbon shell, securely bonded to silicon through dual covalent bonding, effectively shields these pathways, buffering the volume changes and offering an electronically conductive 3D carbon network.

Freely suspended nematic and smectic films and free-standing smectic filaments in the ferroelectric nematic realm.

We show that stable, freely suspended liquid crystal films can be made from the ferroelectric nematic (NF) phase and from the recently discovered polar, lamellar SmZA and SmAF phases. The NF films display two-dimensional, smectic-like parabolic focal conic textures comprising director/polarization bend that are a manifestation of the electrostatic suppression of director splay in the film plane. In the SmZA and SmAF phases, the smectic layers orient preferentially normal to the film surfaces, a condition never found in typical thermotropic or lyotropic lamellar LC phases, with the SmZA films exhibiting focal-conic fan textures mimicking the appearance of typical smectics in glass cells when the layers are oriented normal to the plates, and the SmAF films showing a texture of plaquettes of uniform in-plane orientation where both bend and splay are suppressed, separated by grain boundaries. The SmAF phase can also be drawn into thin filaments, in which X-ray scattering reveals that the smectic layer planes are normal to the filament axis. Remarkably, the filaments are mechanically stable even if they break, forming free-standing, fluid filaments supported only at one end. The unique architectures of these films and filaments are stabilized by the electrostatic self-interaction of the liquid crystal polarization field, which enables the formation of confined, fluid structures that are fundamentally different from those of their counterparts made using previously known liquid crystal phases.

Optimal Strategies for Filament Orientation in Non-Planar 3D Printing

The structural integrity and surface quality of parts produced using traditional fused deposition modeling depend on factors such as layer height, filament and build orientation, print speed, nozzle temperature, and, crucially for this study, both planar and non-planar slicing. Recent research on non-planar slicing techniques has shown significant improvements in surface smoothness and mechanical properties. Key approaches include non-planar slicing for 3-axis printers, adaptive slicing to optimize material placement in critical areas, and post-processing. However, current studies lack a comprehensive method for parameterizing filament direction across both planar and non-planar layers. This work presents an approach to generate optimal trajectories for planar and non-planar layers using contours derived from level set functions. The methodology demonstrates the advantages of non-planar printing, particularly with a filament orientation of 30° for inclined surfaces, ensuring better surface quality, uniformity, and structural integrity. This emphasizes the importance of trajectory planning and filament orientation in achieving high-quality prints on inclined geometries. This research highlights the necessity of a methodology that tailors filament paths based on the load-bearing requirements of each part, demonstrating its potential to enhance surface quality and structural performance, and further the advancement of the 3D printing industry.

Scale Modeling of the Influence of Multiple Localized Defects of Metal Surface on Optical Ellipsometry Results

The work is devoted to the problem of ellipsometric studies of real surfaces and considers the case when surface inhomogeneities are individual localized defects or conglomerates with a size comparable to the wavelength of the probing radiation. Such inhomogeneities lead to angular dependences of ellipsometric parameters that have a non-classical form and cannot be described using conventional well-known models of homogeneous planar layers. This work focuses on the influence of conglomerates of localized defects on the angular dependences of ellipsometric parameters and serves as a continuation of earlier studies in which single localized defects were considered. The dependence of the degree of influence of the distance between defects on the ellipsometric parameters is examined. The parameter “critical distance” between defects is introduced, beyond which they can be considered as localized, and estimates of this parameter for the considered configurations are provided.

Effect of Triterpenoids Betulin and Betulinic Acid on Pulmonary Surfactant Membranes.

The purpose of this work is to examine how triterpenoids betulin (BE) and betulinic acid (BA) affect the thermotropic phase behaviour and bilayer packing in pulmonary surfactant membranes. Therefore, the interaction of these triterpenoids with dipalmitoylphosphatidylcholine (DPPC) bilayers is studied by differential scanning calorimetry (DSC), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, atomic force microscopy (AFM), field emission scanning electron microscopy (FE-SEM), and quantum chemical computations with density functional theory (DFT). From DSC data, the effects are more pronounced with BE compared to BA. At BE concentration of 20mol%, the pretransition does not completely disappear and the lamellar phase transition broadens further. There are two indistinguishable peaks in the main phase transition, which may indicate the start of inhomogeneous mixing or phase separation in the gel phase. BA reduces the main transition temperature and almost completely eliminates the pretransition at concentrations of 1-10mol%. Endotherms continue to have a symmetric, broad form that suggests perfect mixing. From ATR-FTIR data, both triterpenoids display the CH2 antisymmetric stretching, C = O stretching, PO2- asymmetric stretching to higher wavenumber in DPPC system. These results indicate an increase in the lateral mobility and dehydration in the polar head group and glycerol-acyl chain interface of DPPC liposomes. From microscopic results, it is found that the addition of high concentration (20mol%) of BE and BA into pure DPPC membranes, single and double planar layers are formed, and the size of the liposomes increases. According to computational studies, the O131-H206 OH group of BE and the P24-O26 head group of DPPC formed a hydrogen bonding of 1.805Å between BE and DPPC in gas phase. This hydrogen bonding is observed between BA and DPPC via the P24-O26 head group of DPPC and the O132-H209 OH group of BA.

Efficient Snell’s law solution for generating robust acoustic tweezers in dual-layered media

Acoustic tweezers can trap and manipulate a target along a desired path without physical contact. Potential applications of this technology may require the propagation of acoustic waves through non-homogeneous media. It is typically assumed that the acoustic impedance of media is the same. However, this assumption leads to reduced efficiency in both the trapping accuracy and strength of the acoustic tweezers. In this study, we propose a method to derive phases driving an 8x8 array of ultrasonic transducers using generalized Snell’s law to account for the variation in the speed of sound between media layers of planar or non-planar interfaces. The results indicate that the tweezers formed with our approach maintain their patterns and trapping capability at selected trapping locations. In addition, our method significantly enhances the trapping accuracy and force, achieving up to ten times greater force and more accurate alignment with the selected trapping points compared to the previous method that assumes a uniform speed of sound.

Development of a universal plug tray seeder for small seeds based on electrostatic adsorption

Addressing the limitations of the traditional air suction plug tray seeder regarding versatility, clogging, noise, and energy consumption, a novel plug tray seeding method suitable for a broader range of small seed sizes has been proposed. A universal plug tray seeder has also been designed based on electrostatic adsorption for small seeds. Key factors affecting seed electrostatic adsorption were analyzed through electrostatic simulation, determining the optimal manufacturing method for the suction needle and the best range for the electrostatic voltage. Leveraging the theory of granular dynamics, a seed vibration box was designed using the principle of microphone vibration to enhance seed flowability and reduce the multiple seeding rate. Furthermore, the control system achieved seed recognition based on YOLOv8n and adaptive matching of seeding parameters, enhancing the universality of the seeder. The seeder was optimized and validated through practical experiments, with a comparative analysis of energy consumption and sound intensity conducted. The results indicated that the electrostatic suction needle, made with a single copper electrode of 1 mm diameter and coated with a 1 mm thick planar epoxy resin adsorption layer, along with an electrostatic voltage of 5 ∼ 10 kV, could effectively adsorb seeds. The vibration box significantly improved the seeding effect by vibrating seeds of tomato, pepper, and muskmelon at frequencies of 10 ∼ 25 Hz, and seeds of broccoli, cabbage, and eggplant at frequencies of 30 ∼ 50 Hz. The combined action of the electrostatic suction needle and the vibrating seed box resulted in an 83.20 % reduction in energy consumption and a significant decrease in sound intensity. Although the single seeding rate for muskmelon and cabbage seeds slightly decreased due to higher rates of leakage seeding and multiple seeding, the single seeding rate for other seeds remained around 90 %. This study provides a theoretical foundation for the universal seeding method of small seeds and offers significant reference value for the design of low-energy, low-noise plug tray seeders.

(Invited) A Solvent-Free, Thermally Curable Low-Temperature Organic Planarization Layer for Thin Film Encapsulation

Thin film encapsulation (TFE) is an essential component to ensure reliable operation of environmentally susceptible organic light-emitting diode (OLED)-based display. In order to integrate defect-free TFE on display with complex surface structures, additional planarization layer is imperative to planarize the surface topography. The thickness of conventional planarization layer is as high as tens of µm, but the thickness must be reduced substantially to minimize the light leakage in smaller devices such as micro light- emitting diodes (LEDs). In this study, a thin – less than 2 µm – planarization was achieved via solvent-free process, initiated chemical vapor deposition (iCVD). By adapting copolymer from two soft, but curable monomers, glycidyl acrylate (GA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA), excellent planarization performance was achieved on various nano-grating patterns. With only 1.5 µm-thick iCVD planarization layer, a 600 nm-deep trench polyurethane acrylate (PUA) pattern was flattened completely. The TFE fabricated on planarized pattern exhibit excellent barrier property as fabricated on flat glass substrate, which strongly suggests that iCVD planarization layer can serve as a promising planarization layer to fabricate TFE on various types of complicated device surfaces.

Acetylene Synthesis from CO2 and H2O Via Electrochemical Formation of Metal Carbides in High-Temperature Chloride Melt

Research on CO2 conversion into valuable materials has attracted much attention, aiming to realize carbon neutrality and carbon-negative emission technology. It has been reported that the unique physicochemical properties of high-temperature molten salt, such as high conductivity and wide electrochemical window, make it possible to obtain solid carbon directly from CO2 and metal carbides.In this study, we focused on the electrochemical formation of CaC2 from CO2 in high-temperature chloride melt. CaC2 is the raw material for acetylene, the starting material for various chemical products. This study demonstrated the selective formation of CaC2 from CO2 by an electrochemical process in NaCl-KCl-CaCl2-CaO melt at 823 K to produce C2H2 with high current efficiency. When the inert material for oxygen evolution in the high-temperature melts was used as the anode, the formation of acetylene and oxygen from carbon dioxide and water can be realized as the total reaction.2CO2 + H2O → C2H2 + 5/2O2 On the metal cathode, the CaC2 was formed through two reactions: the carbon electrodeposition from CO2-derived CO3 2− (Step 1) and the electrochemical reduction of Ca(II) ion on the carbon (Step 2). These two reactions could be controlled by conducting potentiostatic electrolysis under CO2 and Ar atmospheres, resulting in acetylene synthesis with a maximum current efficiency of 92%. The electrolysis on carbon electrodes revealed that the higher the crystallinity of carbon, the more selectively CaC2 was formed. The CaC2 formation was induced by the reduction of Ca(II) ions on the basal plane of the graphite layer rather than the edge plane. The unique interfacial phenomenon between high-temperature melt and a carbon electrode surface will contribute to realizing a highly efficient CO2 conversion process to acetylene. It was found that the electrochemical formation of CaC2 tends to proceed at the basal plane of the graphite layer. This reaction mechanism is entirely different from the interlayer reactions that tend to occur in LIBs and is unique to this electrolytic system at the carbon/molten salt interface. The obtained data will provide a highly efficient process for CO2 resource conversion and physicochemical insights into new carbon surface reactions.

Outer Helmholtz plane adsorption regulation to achieve low-concentration of pure propylene carbonate solvent electrolytes compatible with graphite anode

The low melting point and high polarity of propylene carbonate (PC) make it an ideal solvent for electrolytes of lithium-ion batteries (LIBs), but the incompatibility with graphite anode hinders the application. In the present study, a new method is developed to solve this problem from a new viewpoint. Introduction of saturated LiNO3 (0.14 mol L‒1) into pure PC electrolyte containing lithium salt with normal concentration (1.38 mol L‒1) leads to a perfect compatibility with graphite anode. Li/Graphite cell using this pure PC electrolyte shows a reversible capacity of 350.0 mAh g‒1 and a 200-cycle capacity retention of 96.3 %. Further mechanism study and theoretical computation indicate that the NO3‒ anions are adsorbed to outer Helmholtz plane of the electric double layer at the graphite anode interface. This changes the Li+ solvation structure in the electric double layer, facilitating the Li+ desolvation process hence resulting in high compatibility with the graphite anode. The most prominent advantage of the present strategy is that, because of the adsorption of NO3‒ anions to the outer Helmholtz plane, the compatibility with graphite anode could be improved by introduction of tiny amount of Li salt without large change of the bulk phase properties of the electrolyte. This work provides a new understanding of the compatibility from the viewpoint of outer Helmholtz plane, which might deliver new insights for the optimization of electrolytes for LIBs.

Fabrication and Characterization of Biocompatible Multilayered Elastomer Hybrid with Enhanced Water Permeation Resistance for Packaging of Implantable Biomedical Devices.

This study presents the synthesis and characterization of hexadecyl-modified SiO2 (HD-SiO2) nanoparticles and their application in the fabrication of a multilayered elastomer hybrid sheet to enhance water resistance in implantable biomedical devices. The surface modification of SiO2 nanoparticles was confirmed via FT-IR and TGA analyses, showing the successful grafting of hydrophobic hexadecyl groups. FE-SEM and DLS analyses revealed spherical HD-SiO2 nanoparticles with an average size of 360 nm. A multilayered elastomer hybrid sheet, consisting of a PDMS-based circuit-protecting body, a water resistance layer of HD-SiO2, a planarization layer, and a biocompatible layer of polydopamine, was fabricated and characterized. The water resistance layer exhibited superhydrophobic properties, with a water contact angle of 154.7° and a 27% reduction in water vapor transmission rate (WVTR) compared to the circuit-protecting body alone. The device packaged with both the circuit-protecting body and water resistance layer demonstrated a tenfold increase in operational lifespan in water medium compared to the device without the water resistance layer. Cytotoxicity and cell proliferation tests on human dermal fibroblast cells (HDFn) confirmed the biocompatibility of the multilayered sheet, with no significant cytotoxicity observed over 48 h.

Effects of Anisotropy, Convection, and Relaxation on Nonlinear Reaction-Diffusion Systems

The effects of relaxation, convection, and anisotropy on a two-dimensional, two-equation system of nonlinearly coupled, second-order hyperbolic, advection–reaction–diffusion equations are studied numerically by means of a three-time-level linearized finite difference method. The formulation utilizes a frame-indifferent constitutive equation for the heat and mass diffusion fluxes, taking into account the tensorial character of the thermal diffusivity of heat and mass diffusion. This approach results in a large system of linear algebraic equations at each time level. It is shown that the effects of relaxation are small although they may be noticeable initially if the relaxation times are smaller than the characteristic residence, diffusion, and reaction times. It is also shown that the anisotropy associated with one of the dependent variables does not have an important role in the reaction wave dynamics, whereas the anisotropy of the other dependent variable results in transitions from spiral waves to either large or small curvature reaction fronts. Convection is found to play an important role in the reaction front dynamics depending on the vortex circulation and radius and the anisotropy of the two dependent variables. For clockwise-rotating vortices of large diameter, patterns similar to those observed in planar mixing layers have been found for anisotropic diffusion tensors.

Efficient equivalent-layer technique for processing irregularly spaced magnetic data on uneven surfaces

We present a new rapid and robust equivalent layer method for processing large magnetic data sets that can deal with irregularly spaced data points on undulating surfaces. Our method estimates an equivalent layer by numerically solving the upward continuation integral for a given set of magnetic data. While this estimated layer allows performing specific spatial transformations such as interpolation and continuations of any potential-field data, it cannot be used to perform conventional phase transformations on magnetic data, such as the reduction to the pole, because it requires a magnetic moment distribution over the equivalent layer of dipoles. To overcome this drawback, we transform the estimated equivalent layer into a planar equivalent layer of dipoles that equally reproduces the observed magnetic data. To carry out this transformation, we first use the fact that the estimated layer obtained by solving the upward continuation integral is a scaled version of the magnetic data on the layer plane, i.e., it can be considered a harmonic function. Then we use the upward continuation integral to continue the estimated layer into a planar and regular grid, which results in a second equivalent layer. Finally, we apply a fast 2D discrete convolution to transform this second layer into a planar equivalent layer of dipoles that also fits the observed magnetic data. Applications to synthetic and real data show that our methodology is able to efficiently process magnetic data, combining the robustness of accommodating irregularly spaced data with the ability to perform phase transformations.

Half-metallic behavior and anisotropy of two-dimensional MoSi2N4/ScSi2N4 heterojunction

Heterojunctions formed by stacking different two-dimensional monolayer materials typically have tunable electronic properties, which will greatly broaden the application prospects of 2D materials in electron devices. In this paper, the structures, electron properties, and anisotropy of MoSi2N4/ScSi2N4 heterojunctions formed by stacking MoSi2N4 monolayer with semiconductor properties and ScSi2N4 monolayer with half-metallic properties have been systematically studied. The results show that Type-Ⅰ configuration has the most stable structure in terms of total energy, binding energy, phonon spectrum and molecular dynamics among the three configurations formed by MoSi2N4/ScSi2N4 heterojunctions. The MoSi2N4/ScSi2N4 heterojunction has robust half-metallic behavior and tensile anisotropy at equilibrium. At the same time, MoSi2N4/ScSi2N4 heterojunction can still maintain stable ferromagnetic and half-metallic properties under large interlayer distance changes. Studies of magnetic anisotropy show that the direction of hard axis for MoSi2N4/ScSi2N4 heterojunction is perpendicular to the 2D layer plane. The tunable properties of MoSi2N4/ScSi2N4 heterojunction provides promising exploration for novel 2D materials.

Local Orientation Transitions to a Lying Helix State in Negative Dielectric Anisotropy Cholesteric Liquid Crystal

Orientation transitions in a cholesteric liquid crystal (CLC) layer with negative dielectric anisotropy, under the influence of a non-uniform spatially periodic electric field created using a planar system of interdigitated electrodes, were studied experimentally and numerically. In the interelectrode space, transitions are observed from a planar Grandjean texture, with the helix axis perpendicular to the layer plane, to states with a lying helix, when the helix axis is parallel to the layer plane and perpendicular to the electrode stripes. It was found that the relaxation time of the induced state in the Grandjean zones, corresponding to two or more half-turns of the helix, significantly exceeded the relaxation time for the first Grandjean zone with one half-turn. An analysis of experimentally observed and numerically simulated textures shows that slow relaxation to the initial state in the second Grandjean zone, as well as in higher-order zones, is associated with the formation of local topologically equivalent states. In these states, the helix has a reduced integer number of helix half-turns throughout the layer thickness or unwound into the planar alignment state.

Solvent-vapor-assisted crystallization of covalent organic framework films for CO2/CH4 separation

Abstract Covalent organic framework films were prepared using alternating vapor deposition of precursors followed by solvent vapor annealing. When an as-deposited film was annealed in appropriate solvent vapors, the prepared covalent organic framework film exhibited an “onion-like” structure. This result opens a way to synthesize covalent organic framework films with highly ordered planar layers through the interaction between layers. The CO2/CH4 separation performance of covalent organic framework film was significantly improved due to the decrease in defects caused by crystallization.

Near‐Infrared Imaging Highly Enhanced by Pixel‐Level Integrated Plasmonic Metasurfaces on CMOS Image Sensors

AbstractNear‐infrared (NIR) photodetection and imaging have sparked significant interests across a wide range of applications. While silicon photodiodes are commonly employed, the small light absorption coefficients of Si in NIR severely limit the performance, especially in the case of thin active Si layers. Although various light harvesting techniques are proposed to increase light absorption of Si, pixel‐level strategy for enhanced NIR imaging is still challenging in CMOS image sensors (CISs) with a pixel size in only a micron scale. In this paper, plasmonic metasurfaces are intimately integrated on top of 2.3 µm thick Si active regions of the pixels of a backside illumination (BI)‐CIS for NIR imaging for the first time. 200% improved photoresponsivity is obtained in experiments in such a planar Si layer rather than patterning the Si layer with potential damage to the active region. Numerical simulation results reveal highly enhanced light intensity in the thin active Si layer due to the presence of plasmonic metasurfaces. Significantly improved imaging brightness and signal‐to‐noise ratio of NIR imaging are demonstrated under both laser and LED illumination. This CMOS‐compatible technique is expected to hold promising potentials in applications including machine vision, iris certification, light detection and ranging (LiDAR), and optical communication in data centers.

Epitaxy of GaSe Coupled to Graphene: From In Situ Band Engineering to Photon Sensing.

2D semiconductors can drive advances in quantum science and technologies. However, they should be free of any contamination; also, the crystallographic ordering and coupling of adjacent layers and their electronic properties should be well-controlled, tunable, and scalable. Here, these challenges are addressed by a new approach, which combines molecular beam epitaxy and in situ band engineering in ultra-high vacuum of semiconducting gallium selenide (GaSe) on graphene. In situ studies by electron diffraction, scanning probe microscopy, and angle-resolved photoelectron spectroscopy reveal that atomically-thin layers of GaSe align in the layer plane with the underlying lattice of graphene. The GaSe/graphene heterostructure, referred to as 2semgraphene, features a centrosymmetric (group symmetry D3d) polymorph of GaSe, a charge dipole at the GaSe/graphene interface, and a band structure tunable by the layer thickness. The newly-developed, scalable 2semgraphene is used in optical sensors that exploit the photoactive GaSe layer and the built-in potential at its interface with the graphene channel. This proof of concept has the potential for further advances and device architectures that exploit 2semgraphene as a functional building block.

Oscillatory excitation of Faraday waves on the interface of immiscible fluids in a slotted channel

Recent studies of the oscillatory dynamics of the interface between fluids in Hele–Shaw cells have revealed a new type of instability termed the “oscillatory Saffman instability” in the case of fluids with high-viscosity contrast. The present study is dedicated to the experimental investigation of the dynamics of the interface between low-viscosity fluids of different densities oscillating in a vertical narrow channel. It is discovered that as the amplitude of oscillations increases, a threshold excitation of parametric oscillations of the interface in the form of a standing wave is observed in the plane of the fluid layer. This phenomenon bears a resemblance to Faraday waves, but the dependence of the standing wave wavelength on the oscillation frequency does not align with the classical dispersion relation for low-viscosity fluids. The damping effect of viscous boundary layers near the cell walls and the out-of-plane curvature of the oscillating interface leads to a decrease in the natural frequency of oscillations. The experiments demonstrate a significant role of the dimensionless layer thickness. With its decrease (increase in the dimensionless out-of-plane interface curvature), the threshold oscillation acceleration rises in accordance with a power law. To the best of the authors' knowledge, this type of instability has been discovered and studied for the first time. Another important finding is the excitation of intense time-averaged vortical flows in the channel plane within the supercritical region. The physical mechanism underlying the excitation of the time-averaged vortices is clarified, and the dimensionless parameters that govern their intensity are identified.

Effect of surface alignment on electric-field-induced phase transitions in blue phases

This study investigates the critical electric field thresholds required for phase transitions in the blue phases of liquid crystals (BPs) confined within vertical field switching cells. BPs are attractive for electro-optical applications due to their polarization-independent response and fast switching times; however; challenges remain regarding their limited temperature stability and previously reported high operational voltages. We employ a combined approach of polarized optical microscopy and electrical impedance analysis to identify the electric field thresholds triggering BP transitions to focal conic domains in cells with and without planar polyimide alignment layers. We show that surface alignment layers stabilize the blue phases and allow for higher applied electric fields before transitioning into the focal conic state. This suggests the possibility of a wider operational voltage range in thinner cells with alignment layers. These findings significantly improve our understanding of BPs, addressing key challenges and paving the way for their integration into advanced photonic devices, based on the CMOS technology.