Thin Samples Research Articles

Computational study of the performance of a solar dryer for improvement in the shelf life of the food materials.

In this study, the thermal and drying characteristics of a thin layer food sample were investigated. An indirect type, simple, efficient, and economically feasible solar dryer was fabricated and used for food preservation. However, a dynamic model of a fabricated solar dryer was also presented to gain a better insight into the drying and thermal actions. This model consists of thermal modeling of the drying chamber, solar collector, and solar-dried food sample. The law of conservation of energy was applied to evaluate the temperature at different sections of the solar dryer with respect to drying time. All listed model equations were solved in the MATLAB environment. This study helps to examine the influence of solar radiation on the collector plate temperature, drying chamber temperature, food sample temperature, and performance parameters such as thermal efficiency with respect to drying time. Model data was found in good agreement with experimental data within a 4% error. It is concluded that the drying of food material is affected by air temperature, the collector temperature, mode of heat transfer, and material characteristics such as dimension and mass of the food sample.

On the Effect of Interphase Boundary Energy Anisotropy on Morphologies: A New Type of Eutectic Grain Observed in a Three-Phase Eutectic System

AbstractEutectic microstructures are dramatically affected by the anisotropy in interphase boundary energy. Depending on this anisotropy function, different eutectic grains may grow simultaneously at the same experimental conditions. In all reported quasi-isotropic and anisotropic two-phase and three-phase eutectic grains in thin samples, lamellar morphology is observed and the microstructure is essentially two dimensional (2D), since the interphase boundaries are perpendicular to the sample walls. Using the β(In)–In2Bi–γ(Sn) system and real-time solidification experiments in thin samples, we introduce a unique and new type of anisotropic three-phase eutectic grain, entitled here as “Laminated Matrix with Rods (LMR).” In this grain, due to the anisotropy in In2Bi/γ(Sn) interphase boundary, the evolving phases, and hence, the microstructures observed through the two glass plates of the thin sample are completely different, despite the strong confinement effect. During rotating directional solidification (RDS) experiments, the morphology or the aspect ratio of all phases changes periodically and drastically. Specifically, In2Bi, β(In), and γ(Sn) phases evolve from all being lamellar perpendicular to the sample walls to the matrix, elongated/trapezoidal rods, and a lamella parallel to the sample walls, respectively. Our experimental results show that these morphological transitions are due to change in the interphase boundary orientation with respect to the growth direction. Graphical abstract

Ferroelectric Organic-Inorganic Hybrid Ammonium Halogenobismuthate(III) for Piezoelectric Energy Harvesting.

Halogenobismuthate(III) compounds are of recent interest because of their low toxicity and distinct electrical properties. The utility of these materials as ferroelectrics for piezoelectric energy harvesters is still in its early stages. Herein, we report a hybrid ammonium halogenobismuthate(III) [BPBrDMA]2·[BiBr5], crystallizing in a ferroelectrically active polar noncentrosymmetric Pna21 space group. Its noncentrosymmetric structure was confirmed by the detection of the second harmonic generation response. The ferroelectric P-E hysteresis loop measurements on the thin film sample of [BPBrDMA]2·[BiBr5] gave a saturation polarization (Ps) of 5.72 μC cm-2. The piezoresponse force microscopy analysis confirmed its ferroelectric and piezoelectric nature, showing characteristic domain structures and signature hysteresis and butterfly loops. The piezoelectric energy harvesting attributes of [BPBrDMA]2·[BiBr5] were further probed on its polylactic acid (PLA) composites. The 15 wt % [BPBrDMA]2·[BiBr5]-PLA polymer composite resulted in a high output voltage of 26.2 V and power density of 15.47 μW cm-2. The energy harvested from this device was further utilized for charging a 10 μF capacitor within 3 min.

Quantitative phase imaging by gradient retardance optical microscopy

Quantitative phase imaging (QPI) has become a vital tool in bioimaging, offering precise measurements of wavefront distortion and, thus, of key cellular metabolism metrics, such as dry mass and density. However, only a few QPI applications have been demonstrated in optically thick specimens, where scattering increases background and reduces contrast. Building upon the concept of structured illumination interferometry, we introduce Gradient Retardance Optical Microscopy (GROM) for QPI of both thin and thick samples. GROM transforms any standard Differential Interference Contrast (DIC) microscope into a QPI platform by incorporating a liquid crystal retarder into the illumination path, enabling independent phase-shifting of the DIC microscope's sheared beams. GROM greatly simplifies related configurations, reduces costs, and eradicates energy losses in parallel imaging modalities, such as fluorescence. We successfully tested GROM on a diverse range of specimens, from microbes and red blood cells to optically thick (~ 300 μm) plant roots without fixation or clearing.

Effects of Polarizer-Analyzer Configurations for FTIR Spectroscopy: Implications for Multiple Polarization Algorithms.

Polarized Fourier transform infrared (p-FTIR) spectroscopy is a widely used technique for determining orientational information in thin organic materials. Conventionally, a single polarizer is placed in the path of the incident light (termed the polarizer). Occasionally, a second polarizer is also placed after the sample (referred to as the analyzer). However, this polarizer-analyzer configuration has the potential to induce polarization-dependent variances in the final spectra beyond those that are expected, i.e., the squared-cosine relationship of absorptance with respect to polarization angle is no longer accurate. These variances are due to changes in the polarization state of the transmitted light induced by the sample and have yet to be explored in the context of p-FTIR. Consequently, this study employs both theoretical and experimental approaches to identify the effects of including a second polarizer in p-FTIR analyses of anisotropic organic samples. For thin samples, the most significant spectral variance arising from only birefringence is observed on the shoulders of the dichroic peaks. By adopting a crossed polarizer configuration, it is shown that there is potential to identify anisotropy of samples that are generally considered too thick for p-FTIR analysis by exploiting this feature. Furthermore, the squared-cosine relationship of absorptance with respect to the polarization angle is also shown to be inapplicable when a second parallel-oriented polarizer is included. Accordingly, a function that accounts for the second polarizer is proposed for multiple polarization techniques.

Reliable Method for Estimating Nerve Fiber Density in Epidermis Using Routine Histopathologic Tissue Preparation: A Promising Diagnostic Tool for Small Fiber Neuropathy.

Practical yet reliable diagnostic tools for small-fiber neuropathy are needed. We aimed to establish a histopathologic protocol for estimating intraepidermal nerve fiber density (eIENFD) on formalin-fixed, paraffin-embedded tissue (FFPE), evaluate its reliability through intraobserver and interobserver analyses, and provide normative reference values for clinical use. Sixty-eight healthy participants underwent nerve conduction studies and quantitative sensory testing. Skin biopsies from the distal and proximal leg were taken and processed using routine immunohistochemistry (anti-PGP9.5 antibodies) on thin 5 µm sections. eIENFD was assessed with a modified counting protocol. Interobserver and intraobserver reliabilities were excellent (ICC=0.9). eIENFD was higher in females than males (fibers/mm, 14.3±4.4 vs. 11.6±5.8, P <0.05), decreased with age ( r s =-0.47, P <0.001), and was higher proximally than distally (15.0±5.5 vs. 13.0±5.3, P =0.002). Quantile regression equations for the fifth percentile of distal and proximal eIENFD were presented: 13.125-0.161×age (y)-0.932×sex (male=1; female=0) and 17.204-0.192×age (y)-3.313×sex (male=1; female=0), respectively. This study introduces a reliable and reproducible method for estimating epidermal nerve fiber density through immunostaining on 5-µm thin FFPE tissue samples. Normative data on eIENFD is provided. Regression equations help identify abnormal decreases in small nerve fiber density.

Expanding the Palette of SWIR Emitting Nanoparticles Based on Au Nanoclusters for Single-Particle Tracking Microscopy.

Single-molecule localization microscopy has proved promising to unravel the dynamics and molecular architecture of thin biological samples down to nanoscales. For applications in complex, thick biological tissues shifting single-particle emission wavelengths to the shortwave infrared (SWIR also called NIR II) region between 900 to 2100nm, where biological tissues are more transparent is key. To date, mainly single-walled carbon nanotubes (SWCNTs) enable such applications, but they are inherently 1D objects. Here, 0D ultra-small luminescent gold nanoclusters (AuNCs, <3nm) and ≈25nm AuNC-loaded-polymeric particles that can be detected at the single-particle level in the SWIR are presented. Thanks to high brightness and excellent photostability, it is shown that the dynamics of the spherical polymeric particles can be followed at the single-particle level in solution at video rates for minutes. We compared single particle tracking of AuNC-loaded-polymeric particles with that of SWCNT diffusing in agarose gels demonstrating the specificity and complementarity of diffusion properties of these SWIR-emitting nano-objects when exploring a complex environment. This extends the library of photostable SWIR emitting nanomaterials to 0D nano-objects of variable size for single-molecule localization microscopy in the second biological window, opening unprecedented possibilities for mapping the structure and dynamics of complex biological systems.

Finite-size effects in hyperuniform vortex matter

Novel hyperuniform materials are emerging as an active field of applied and basic research since they can be designed to have exceptional physical properties. This ubiquitous state of matter presents a hidden order that is characterized by the density of constituents of the system being uniform at large scales, as in a perfect crystal, although they can be isotropic and disordered like a liquid. In the quest for synthesizing hyperuniform materials in experimental conditions, the impact of finite-size effects remains as an open question to be addressed. We use vortex matter in type-II superconductors as a toy model system to study this issue. We previously reported that vortex matter nucleated in samples with point disorder is effectively hyperuniform and thus presents the interesting physical properties inherent to hyperuniform systems. In this work we present experimental evidence that on decreasing the thickness of the vortex system its hyperuniform order is depleted. By means of hydrodynamic arguments we show that the experimentally observed depletion can be associated to two crossovers that we describe within a hydrodynamic approximation. The first crossover length is thickness-dependent and separates a class-II hyperuniform regime at intermediate lengthscales from a regime that can become asymptotically non-hyperuniform for large wavelengths in very thin samples. The second crossover takes place at smaller lengthscales and marks the onset of a faster increase of density fluctuations due to the dispersivity of the elastic constants. Our work points to a novel mechanism of emerging hyperuniformity controlled by the thickness of the host sample, an issue that has to be taken into account when growing hyperuniform structures for technological applications.

Azimuthal Scanning Excitation Surface Plasmon Resonance Holographic Microscopy

AbstractSurface plasmon resonance (SPR) holographic microscopy exploits surface plasmon wave as illumination and acquires both SPR intensity and phase images. It detects extremely tiny variations of weakly interacting objects owing to high sensitivity and has been applied in cell biology, material science, surface chemistry, etc. However, it is very challenging to solve the problem of poor spatial resolution due to the transverse propagation of surface plasmon wave. In this paper, an azimuthal scanning excitation method is proposed in SPR holographic microscopy to improve the spatial resolution by engineering the Fourier spectra of SPR images from dual‐arc to circular shape. The study modulates the light field with spatial position, wavevector, and polarization to realize azimuthal scanning excitation of SPR. Systematic experiments of dielectric spheres, nanowires, two‐dimension materials, and complex nanostructure are conducted to show the resolution improvement with one order of magnitude, the higher detection sensitivity of SPR phase than that of SPR intensity, and the necessities of both of high‐resolution SPR intensity and phase images to retrieve sample information in certain scenarios. Benefiting from the high detection sensitivity and spatial resolution, the proposed microscopy will find wide applications in nanoparticle analysis, low‐dimensional material characterization, and imaging extremely thin or transparent samples.

A Study of Nanostructured FeO Thin Film-Based Allure Red and Direct Blue 15 Azo Dyes Sensing Scheme

This study reports on the amperometric sensing properties of FeO/Fe2O3 thin films for the detection of Allura Red (AR) and Direct Blue 15 (DB15) Azo dyes. The FeO/Fe2O3 thin films were produced using the Sequential Ionic Layer Adsorption and Reaction (SILAR) method and Na+-doping. The morphological and structural properties of the nanocomposites produced at pH of 10.5 showed good properties for the detection of azo dyes. The linear curve fit equations for AR and DB15 droplet applications onto Na+-doped FeO nanocomposite thin film samples were found to be y = -0.0002x + 0.0043 (R² = 0.9143) and y = -7E-05x + 0.0005 (R² = 0.9809), respectively. The findings reveal that adding Na+ doping to FeO/Fe2O3 thin films can effectively increase the detection response for the target azo dyes and enhance the sensitivity of the sensing system. The results suggest that the SILAR method can be used to produce low-cost and reusable FeO/Fe2O3 thin film devices, which can be promising candidates for the detection of toxic azo dyes in liquid samples.

Design, characterization, and implementation of Diffuse Reflectance Integrating Ellipsoids (DRIE) for spectroscopic analysis

Integrating ellipsoids in diffuse reflectance spectroscopy is unusual; few are constructed in just one piece. In diffuse reflectance spectroscopy, integrating spheres are used to determine the optical properties of biological tissues in diagnosis or disease detection. The disadvantages of using integrating spheres in the biological field lie in the dimensions of their apertures, which, being small, prevent the analysis of a complete biological tissue or organ. In this work, we propose the construction, calibration, and use of diffuse reflecting integrating ellipsoid (DRIE) for spectral analysis, elaborated as a body without couplings, not implemented so far for clinical diagnosis. A hyperboloid calibrator was designed and coupled to the ellipsoid to measure the volumetric spectra of samples instead of thin samples with small surfaces to measure whole organs or samples with larger sizes than habitual. We developed a radiometric theory for the ellipsoid using the shape factor to calculate its flux or radiant energy. With spectra acquired by the device from different chicken tissues (brain, bone, muscle, digestive tract, and skin) and with support vector machines (SVM), spectra of the tissues were classified for dimensions from 19.14 mm2 to 4600 mm2, resulting in a correlation (0.98), demonstrating the high sensitivity and low noise of our device to classify.

High-strength 91W-6Ni-2Co-1Fe tungsten heavy alloys prepared by laser melting deposition using granulated powder

This study introduces a new approach for fabricating high-strength 91W-6Ni-2Co-1Fe tungsten heavy alloys (WHAs) using laser melting deposition (LMD) with a specially formulated granulated powder, characterized by near-spherical particles and a dense structure with fine W grains (2.6 μm). Thin plate samples were prepared using laser powers from 500 W to 900 W, revealing increased density at higher laser power, while the W grain size remains relatively stable. A near-fully dense sample (99% density) with the finest W grain size of 2.8 μm is obtained at a laser power of 900 W, while the highest hardness of 482 HV is achieved at 700 W. The contributions of the high cooling rate of LMD, the Co addition, as well as the use of fine-grained granulated powder to enhance the high strength are discussed. These findings offer significant insights into optimizing WHA fabrication using LMD, highlighting its potential in advanced materials engineering.

Accelerated corrosion of low carbon steel by oscillatory acidic streams generated with a bio-inspired claw device.

A mechanical device inspired by the pistol shrimp snapper claw was developed. This technology features a claw characterized by a periodic opening/closing motion, at a controlled frequency, capable of producing oscillating flows at transitional Reynolds numbers. An innovative method was also proposed for determining the corrosion rate of carbon steel samples under oscillating acidic streams (aqueous solution of HCl). By employing very-thin carbon steel specimens (25 μm thickness), with one side coated with Zn and not exposed to the stream, it became possible to electrochemically sense the Zn surface once the steel sample was perforated, thus providing the average dissolution rate into the most relevant pit on the steel surface. Furthermore, a laser light positioned beneath the metallic sample, along with a camera programmed to periodically capture images of the steel surface, facilitated the accurate counting of the number of newly formed pits. The system consisting of the thin steel sample and the Zn coating can be seen as a type of corrosion sensor. Furthermore, the proposed laser illumination method allows corroborating the electrochemical detection of pits and also establishing their location. The techniques crafted in this study pave the way for developing alternative corrosion sensors that boast appealing attributes: affordability, compactness, and acceptable accuracy to detect in time and space localized damage.

Improved detection of nonlinear waves in thin solid materials using a pulse-echo method based on nonlinear modeling of wave fields

The nonlinearity parameter is a powerful tool for nondestructive evaluation, as it provides a measure of the state of damage of structural components. When carrying out nonlinearity parameter measurements of solid structures, the pulse-echo method is more suitable than the through-transmission method; however, a planar stress-free boundary is known to destructively alter the nonlinear wave generation process, including the second harmonic component, meaning that the pulse-echo nonlinear method is limited for practical applications, especially for thin solids. In this work, an improved detection method is proposed for the enhancement of nonlinear wave measurement in thin solids using a pulse-echo method with a dual-element transducer consisting of an outer ring transmitter and an inner disk receiver. A multi-Gaussian beam model is developed for the ring transmitter to fast simulate the pulse-echo nonlinear wave fields, and based on the results, improvements for the received nonlinear waves are achieved by optimizing the driving frequency. The advantages of the proposed method are that solid samples with different thicknesses can be evaluated using a dual-element transducer, and a high measurement accuracy can also be achieved for thin solid samples. Experiments are performed to investigate the harmonic waves measured in fatigue-damaged thin steel samples, and the results verify the effectiveness of the proposed method.

Pinning/depinning dynamics of trijunction lines during faceted/nonfaceted eutectic growth

We present an in situ experimental study of decoupled- and coupled-growth patterns in a binary faceted/ nonfaceted (f/nf) eutectic alloy. Real-time optical observation is carried out at low growth velocity V (<0.3μms−1) during directional solidification of the transparent AminoMethylPropaneDiol-Succinonitrile (AMPD-SCN) eutectic in thin samples. On a large scale, the two-phase growth front mostly exhibits irregularly spaced decoupled-growth patterns involving faceted fiber-like AMPD crystals that protrude in the liquid ahead of, and in weak diffusive interaction with the nonfaceted SCN solid. The morphological stability of low-velocity, steady-state decoupled-growth patterns is evidenced. In addition, three types of (f/nf) coupled-growth patterns with fiber-like, tubular (or “hollow”) and C-shaped morphologies, respectively, are identified. New light is cast on the pinning dynamics of trijunctions at which the two solid phases and the liquid meet in equilibrium. A discussion is initiated on the interplay between the interfacial kinetics of the more or less mobile facets and the solute diffusion field, and on the stability of triple junctions with strongly anisotropic interfaces.

Aberration correction for deformable-mirror-based remote focusing enables high-accuracy whole-cell super-resolution imaging

Single-molecule localization microscopy (SMLM) enables three-dimensional (3D) investigation of nanoscale structures in biological samples, offering unique insights into their organization. However, traditional 3D super-resolution microscopy using high numerical aperture (NA) objectives is limited by imaging depth of field (DOF), restricting their practical application to relatively thin biological samples. Here, we developed a unified solution for thick sample super-resolution imaging using a deformable mirror (DM) which served for fast remote focusing, optimized point spread function (PSF) engineering, and accurate aberration correction. By effectively correcting the system aberrations introduced during remote focusing and sample aberrations at different imaging depths, we achieved high-accuracy, large DOF imaging ( ∼8  μm ) of the whole-cell organelles [i.e., nuclear pore complex (NPC), microtubules, and mitochondria] with a nearly uniform resolution of approximately 35 nm across the entire cellular volume.

Investigation on thermoelectric properties of SnSe thin films as prepared by RF magnetron sputtering

In this work, we investigated the thermoelectric properties of SnSe (Tin Selenide) thin films onto SiO2/Si-wafer substrates as prepared by RF (radio frequency) magnetron sputtering technique. The sputtering conditions used base pressure below 5.5 10-4 Pa and working pressure at 0.93 Pa within the Ar atmosphere as a flow rate fixed 40 sccm. The RF sputtering power was applied at 80 W and sputtering time for 30 min. After thin film deposition, as-deposited thin films were annealed by the vacuum annealing method at 300-450 oC. The crystal structure, morphology and film thickness, and atomic composition of SnSe thin film were carried out by X-ray diffraction (XRD), the field emission scanning electron microscope (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) techniques, respectively. The thermoelectric properties (electrical resistivity; ρ) and Seebeck coefficient; S) were measured by the ZEM-3 method to calculate the power factor (PF) value. The results showed that the as-deposited thin films had improved the crystallography of SnSe from amorphous to crystalline phases after thin films were annealed at a temperature range of 300-400 oC. At room temperature, the maximum power factor of 0.35 mW m˗1 K˗2 (ρ = 202 mΩ m and S = 165 μV K˗1) could be found to estimate the dimensionless Figure of Merit (ZT) values around 0.44 for annealing thin film sample at 400 oC.

Enhancing electromagnetic properties in nickel hydroxide modified graphene composites via secondary reactions for improving multi-polarization electromagnetic absorption efficiency

Carbon-based materials exhibit excellent dielectric absorption properties, among which graphene has received particular attention in research of electromagnetic wave absorbing materials because of its high electrical conductivity and unique large-area, thin-layer two-dimensional structural features. However, the electromagnetic absorption performance of the material is hindered from further improvement due to its single component composition. It is influenced by the conductive network of graphene, making it challenging to achieve a balance in impedance matching and electromagnetic loss, thereby restricting its broader application. To address these challenges, we developed a series of nickel hydroxide-modified graphene composites. Through a structural composite design, we optimized overall impedance matching, introduced diverse loss mechanisms to enhance electromagnetic loss performance, and utilized a secondary reaction control method to precisely regulate the deposition of nickel hydroxide on the graphene surface, thereby achieving regulate of the composite material's electromagnetic parameters within a defined range. Under low sample filling ratios and a thin sample thickness of 1.8 mm, the effective absorption bandwidth reaches 6.5 GHz, demonstrating excellent electromagnetic absorption performance. This study provides a controllable design approach for modulating material electromagnetic parameters by influencing the reaction process. It also offers a design method for composites with an outstanding electromagnetic loss mechanism.

Interferometric characterization of high-frequency piezoelectric effects in hydroxyapatite thin films

Hydroxyapatite (HAp) qualities such as biocompatibility and piezoelectricity make it an excellent material for biomedical applications. Here, HAp thin film samples were fabricated onto silica substrates to study their piezoelectric behavior with optical interference. Thin solid films were deposited using previously synthesized HAp powder, sol-gel, and spin-coating techniques. The samples were characterized by scanning electron microscopy, energy dispersive X-ray, Raman, and UV-Vis spectroscopies. The statical piezoelectric effect of the samples was studied by using a finite element method and computational software. Additionally, an experimental Bode analysis allows computing the internal electrical components of the films using high-frequency AC voltage. The electrical behavior is related to the equivalent circuit of a piezoelectric crystal, which indicates the range of frequencies where the electromechanical effect is maximum. A Sagnac interferometer was used to characterize the strain in the HAp as a function of the electrical input frequency. The displacement of the interferometric fringe pattern allows us to estimate the change in the thickness of the sample and compute the piezoelectric constant. The synthesis of HAp thin films with piezoelectric properties provides an effective way to produce sensors and actuators for technological applications.

Synthesis of Iron Copper Sulphide (FeCuS) Thin Film and its Characterization

The Influence of SILAR cycle on the optical, morphological as well as compositional properties of Iron Copper Sulphide (FeCuS) thin film was reported. Utilizing the straightforward and reasonably priced SILAR technique, the deposition was carried out by the use of soda lime glass (SLG) substrates. With a concentration of 1.0M for Iron (Fe) ions, the deposition process was repeated 50, 60, and 70 times, with an 80-seconds dip time per cycle. Morphological characterization of the thin film was analyzed with Scanning Electron Microscopy (SEM) instrument. The compositional properties were analyzed with Energy Dispersive X-Ray machine. A UV-VIS Spectrophotometer was utilized to examine the thin film's optical characteristics. The presence of deposited thin film samples is confirmed by the SEM results, which display higher peaks for the elements Fe, Cu, and S. The results of the EDX analysis demonstrated that an increase in concentration enhances the homogeneity and adhesion of the deposited films in addition to their crystallinity. It was discovered that the thin film's energy band gap for each SILAR cycle was 0.9 eV, 1.3 eV, and 2.99 eV respectively.