Crystal Plates Research Articles

Liquid crystal micro-Fresnel zone plate with fine variable focusing properties

This study presents a liquid crystal micro-Fresnel zone plate (LC-MFZP) with fine variable focusing properties. The LC-MFZPs are fabricated via photochemical processes without any mechanical process. The focusing properties are investigated through numerical simulations and experiments. LC-MFZPs can generate a focusing spot with a specific incident wavelength such that the transmitted phase difference between their adjacent ring zones is π rad. When this difference is changed by the electrical reorientation of the LCs, the focusing spot disappears because the diffraction condition is no longer satisfied. Subsequently, another focusing spot at a specific incident wavelength is generated to satisfy the diffraction condition. The positions of these focusing spots differ because the focal lengths depend on the incident wavelength. Consequently, LC-MFZPs can be used to electrically control the focal length. This study may find applications in optical manipulation and optical trapping.

Intense ultraviolet–visible–infrared full-spectrum laser

A high-brightness ultrabroadband supercontinuum white laser is desirable for various fields of modern science. Here, we present an intense ultraviolet-visible-infrared full-spectrum femtosecond laser source (with 300–5000 nm 25 dB bandwidth) with 0.54 mJ per pulse. The laser is obtained by sending a 3.9 μm, 3.3 mJ mid-infrared pump pulse into a cascaded architecture of gas-filled hollow-core fiber, a bare lithium niobate crystal plate, and a specially designed chirped periodically poled lithium niobate crystal, under the synergic action of second and third order nonlinearities such as high harmonic generation and self-phase modulation. This full-spectrum femtosecond laser source can provide a revolutionary tool for optical spectroscopy and find potential applications in physics, chemistry, biology, material science, industrial processing, and environment monitoring.

Determination of the polarization plane specific rotation in gyrotropic crystals of the middle category by the spectrophotometric method

A large number of modern functional single crystals of the middle category belong to gyrotropic media. In these crystals, when light propagates along the optical axis, rotation of the plane of its polarization is observed. In this work a spectrophotometric method was used to obtain the dispersion dependences of the rotation angle of the polarization plane. This method is based on measuring the intensity of light passing through the polarizer–crystal–analyzer system, the crystal is a polished plane-parallel plate of a uniaxial gyrotropic crystal cut perpendicular to the optical axis. Measurements were carried out on a UV-Vis-NIR spectrophotometer Cary-5000 in the wavelength range of 200—1200 nm using polarizers — Glan–Taylor prisms. Polished plane-parallel plates of known SiO2 and α-LiIO3 crystals were used as samples. The obtained dispersion dependences of the spectral transmission coefficients are oscillating. Discrete values of the specific angles of rotation of the plane of polarization of light are calculated from the extremes on these dependencies. These discrete values can be approximated by the formulas Drude, Chandrasekhar and Vyshina, depending on what determines the nature of the rotational ability of the plane of polarization of light in each particular material. For the studied crystals, dependences of the modified Drude formula of the form 1/ρ = f(λ2) are plotted, these dependences should have a linear character in the case of an ideal crystal. The obtained experimental results correlate well with the available literature data. The advantages of this method are efficiency, the possibility of obtaining dispersion dependences of the specific rotation angle of the polarization plane, the need for a single sample, the possibility of assessing the nature of the rotational ability of specific crystals, the possibility of evaluating the structural perfection of the studied crystals.

Theoretical and experimental demonstrations of the transversely symmetric and antisymmetric properties of topological edge states

Topological phononics are well known for their topological edge states (TES) due to backscattering immunity and pseudospin-dependent phonon transport. Here, we study two types of TES on valley phononic crystal (PC) plates. We magnify the transversely symmetric and antisymmetric properties by observing the displacement distribution in both simulations and experiments. We underline the theoretical origin of transversely symmetric and antisymmetric properties based on a simplified mass-spring model, i.e. the combination of the phase difference caused by the periodicity of the PC plate and the phase difference between sites p and q in the unit cell. Our results enrich the features of TES and offer the possibility of designing mechanical devices or controlling wave propagation along phonon circuits.

Low frequency elastic waves and vibration control mechanism of innovative phononic crystal thin plates

In order to realize the metamaterials that can control low-frequency vibration and be applied to practical engineering, an innovative phononic crystal thin plate is proposed in this paper. The band gap of the thin plate is systematically analyzed according to the existing wave theory and finite element method. According to the design characteristics of thin plate structure, the influence of the thickness and material of the upper and lower plates and intermediate layers of thin plate on the band gap is explored. Then, the energy propagation behavior of the wave in the structure is briefly discussed. Finally, the control effect of thin plate structure on vibration is verified by numerical simulation. The results show that the phononic crystal plate constructed by us is not only simple in structure design and easy to implement, but also has good band gap tuning and vibration attenuation effect.

Geometric eccentricity effect on thickness-shear vibration of an elliptical flexoelectric crystal plate

In this paper, a thickness-shear vibration model for a two-dimensional finite flexoelectric crystal plate with slowly varying thickness and elliptical cross section is presented. The influences of eccentricity and flexoelectricity on the fundamental frequencies of thickness-shear vibration and electric potential distributions under short circuit boundary condition are investigated. The proposed model uses the first order McLaughlin series to approximate the elliptical function and the first derivative of elliptical function is ignored since the plate thickness varies slowly. For the finite plate, the symmetric mode in length and antisymmetric mode in thickness are adopted for the displacement function. In addition, only the shear strain gradient through the thickness is used in the mathematical model for the thin and long flexoelectric crystal plate. By implementing the variational principle, the governing equations are obtained and further solved by the Galerkin method. The obtained frequencies of thickness-shear mode are expressed in terms of eccentricity and length-to-thickness ratio. The results show that the eccentricity has great influence on the nondimensional fundamental frequencies. A small reduction in eccentricity results in significant increment of the nondimensional frequency implying that it is possible to increase the fundamental frequency by changing the cross section of the elliptical flexoelectric plate. The flexoelectric effect is also found to affect the nondimensional frequency and electric potential distribution significantly. Thus, for accurate design of nano/micro scale high precision and high frequency flexoelectric/piezoelectric devices, flexoelectricity must be taken into consideration.

Preparation and Characterization of Metal-Organic Framework Coatings for Improving Protein Crystallization Screening.

Modifying crystallization plates can significantly impact the success rate and quality of protein crystal growth, making it a helpful strategy in protein crystallography. However, appropriate methods for preparing nano-sized particles with a high specific surface area and strategies for applying these nanoparticles to form suitable coatings on crystallization plate surfaces still need to be clarified. Here, we utilized both an ultrasonic crusher and a high-pressure homogenizer to create a nano metal-organic framework (MOF), specifically HKUST-1, and introduced a solvent evaporation method for producing MOF coatings on 96-well crystallization plates to induce protein crystal growth. The morphology of MOF coatings on the resin surface of the plate well was characterized using optical and scanning electron microscopy. Compared to the control group, crystallization screening experiments on nine proteins confirmed the effectiveness of plates with MOF coatings. Applying MOF coatings to crystallization plates is an easy-to-use, time-efficient, and potent tool for initiating crystallization experiments.

Evaluation of Local Stress Distributions and Dislocations Around Petal Patterns Observed in CVD Single Crystal Diamond Plates

Evaluation of Local Stress Distributions and Dislocations Around Petal Patterns Observed in CVD Single Crystal Diamond Plates

Materials in the CaO-K2O-SO3-H2O System Based on Powder Mixtures including Calciolangbeinite K2Ca2(SO4)3 and Calcium Sulfate Anhydrite CaSO4

Materials (cement stone samples) in the CaO-K2O-SO3-H2O system with the target phase compositions, including syngenite K2Ca(SO4)2·H2O and calcium sulfate dihydrate CaSO4·2H2O, were prepared from powder mixtures of calcium sulfate anhydrite CaSO4, and/or calciolangbeinite K2Ca2(SO4)3, and potassium sulfate K2SO4 via hydration reactions at a water/powder ratio within an interval of 0.5–0.9. It was revealed that samples with contents of 25, 50, 75 and 100 mol% of syngenite K2Ca(SO4)2·H2O demonstrated a nonlinear dependence of their respective microstructures on their phase compositions. The microstructures of samples with phase compositions of 25 and 75 mol% of syngenite K2Ca(SO4)2·H2O consisted of pillar crystals. The microstructures of samples with phase compositions of 50 and 100 mol% of syngenite K2Ca(SO4)2·H2O consisted of plate crystals. An explanation of microstructure formation was set forth, taking into account equilibria of the dissolution–crystallization processes during cement stone formation. Materials obtained in the CaO-K2O-SO3-H2O system consisting of biocompatible and resorbable (soluble in water) phases can be recommended for testing as potential substances for bone defect treatments.

Design of a Functionally Graded Material Phonon Crystal Plate and Its Application in a Bridge

In order to alleviate the structural vibrations induced by traffic loads, in this paper, a phonon crystal plate with functionally graded materials is designed based on local resonance theory. The vibration damping performance of the phonon crystal plate is studied via finite element numerical simulation and the band gap is verified via vibration transmission response analysis. Finally, the engineering application mode is simulated to make it have practical engineering application value. The results show that the phonon crystal plate has two complete bandgaps within 0~150 Hz, the initial bandgap frequency is 0.00 Hz, the cut-off frequency is 128.32 Hz, and the internal ratio of 0~100 Hz is 94.13%, which can effectively reduce the structural vibration caused by traffic loads. Finally, stress analysis of the phonon crystal plate is carried out. The results show that phonon crystals of functionally graded materials can reduce stress concentration through adjusting the band gap. The phonon crystal plate designed in this paper can effectively suppress the structural vibration caused by traffic loads, provides a new method for the vibration reduction of traffic infrastructure, and can be applied to the vibration reduction of bridges and their auxiliary facilities.

Vibrational loss analysis of a new type of phononic crystal with a tungsten block embedded inside a rubber matrix

Vibration and noise pollution is one of the main pollution in modern society. In order to obtain good vibration damping effect, more effective phononic crystals should be designed. Based on the theory of elastic wave propagation in solids, three types of phononic crystals are designed in this paper using tungsten blocks embedded in a rubber matrix, which are cup-shaped phononic crystal, solid cylindrical phononic crystal, and hollow cylindrical phononic crystal. Firstly, the band gap characteristics and vibration losses of the three phononic crystals are analyzed by using the finite element method. Secondly, the physical mechanism of band gap formation is explored by vibration modes. Finally, the cup-shaped phononic crystal was introduced into the core layer of the sandwich plate to form the cup-shaped phononic crystal sandwich plate, and its vibration damping performance was analyzed. The results show that the three phononic crystals can form three band gaps in the range of 0–800 Hz, and the first low-frequency band gap starts at about 140 Hz and is all wider than 200 Hz. It is noteworthy that the average loss of vibration transmission of the three types of phononic crystals is more than 69 dB, which possesses stronger damping capability and wider low- and middle-frequency band gaps than the flat plate type phononic crystals. The vibration direction of the phononic crystal is at an angle of 90° to the wave vector, which prevents the propagation of elastic waves. The phononic crystal embedded in the sandwich panel plate is more in line with the actual demand of vibration damping and obtains good vibration damping effect. The research in this paper can provide more feasibility for phononic crystal damping.

Analysis of Vibration-Damping Characteristics and Parameter Optimization of Cylindrical Cavity Double-Plate Phononic Crystal.

For the application of low-frequency vibration damping in industry, a cylindrical cavity double-layer plate-type local resonance phononic crystal structure is proposed to solve low-frequency vibration in mechanical equipment. Initially, using COMSOL 5.4 software, the bending wave band gap is calculated in conjunction with elastic dynamics theory and the BOLOCH theorem to be 127-384 Hz. Then the mechanism of bending wave gap is analyzed by combining element mode shape and an equivalent model. Subsequently, the bending vibration transmission characteristics of the crystal plate are explained, and the vibration-damping characteristics are illustrated in combination with the time-frequency domain. An experimental system is constructed to verify the vibration-damping properties of crystal plates; the experimental results and simulation results are verified with each other. Finally, the element structural parameters are optimized using the RSM. Fifty-four sets of experiments are designed based on six structural factors and three levels, and the expressions between the bending wave band gap and six structural factors are obtained. Combining the particle swarm algorithm, the optimization is performed with the band gap width as the target. This method is shown to be more accurate than the commonly used interior point method. The structure of cylindrical-cavity-type phononic crystal and the parameter optimization method proposed in this paper provide a certain reference for the design of local-resonance-type phononic crystal.

Fabrication of azimuthally/radially symmetric liquid crystal plates using two-step photoalignments.

Fabrication of azimuthally/radially symmetric liquid crystal plates (A/RSLCPs) using two-step photoalignments with the two dichroic dyes methyl red (MR) and brilliant yellow (BY) is demonstrated. BY molecules coated onto a substrate and MR molecules doped in LCs in a cell can azimuthally and radially align LCs by illuminating radially and azimuthally symmetric polarized light with specific wavelengths, respectively. In contrast to the previous fabrication methods, the fabrication method proposed here can prevent the contamination/damage of photoalignment films on substrates. A method to improve the proposed fabrication to avoid generating undesirable patterns is also elucidated.

Effects of Flotation Reagents on the Morphology of Magnesium Hydroxide: Experimental and Simulation Study

The flotation process to extract potassium salt from carnallite ores could produce the MgCl2 mother liquor with flotation reagents─octadecyl amine hydrochloride (ODA) and dodecyl morpholine (DMP). The organic impurities would further affect MgCl2 resource-integrated utilization for preparing magnesium hydroxide (MH). In this study, the effects of flotation reagents with different concentrations on the morphology of MH were investigated at a hydrothermal temperature of 200 °C for 6 h with the hydrothermal medium of a 4 mol/L NaOH solution. It was observed that the average thickness of MH crystal plates increased and the morphology of crystals changed from regular hexagonal plates to irregular polygonal plates with the increase of ODA and DMP concentrations. Molecular dynamics (MD) simulation was applied to further explain the effect mechanism. The results indicated that ODA and DMP molecules were more likely to be adsorbed on the (1 1 0) plane in contrast to the (0 0 1) plane due to the larger absolute values of adsorption energy on the (1 1 0) plane. The long carbon chains far away from the (1 1 0) plane would form steric hindrance to affect the growth rate of MH crystals in the [1 1 0] direction.

Crystal search - feasibility study of a real-time deep learning process for crystallization well images.

To avoid the time-consuming and often monotonous task of manual inspection of crystallization plates, a Python-based program to automatically detect crystals in crystallization wells employing deep learning techniques was developed. The program uses manually scored crystallization trials deposited in a database of an in-house crystallization robot as a training set. Since the success rate of such a system is able to catch up with manual inspection by trained persons, it will become an important tool for crystallographers working on biological samples. Four network architectures were compared and the SqueezeNet architecture performed best. In detecting crystals AlexNet accomplished a better result, but with a lower threshold the mean value for crystal detection was improved for SqueezeNet. Two assumptions were made about the imaging rate. With these two extremes it was found that an image processing rate of at least two times, but up to 58 times in the worst case, would be needed to reach the maximum imaging rate according to the deep learning network architecture employed for real-time classification. To avoid high workloads for the control computer of the CrystalMation system, the computing is distributed over several workstations, participating voluntarily, by the grid programming system from the Berkeley Open Infrastructure for Network Computing (BOINC). The outcome of the program is redistributed into the database as automatic real-time scores (ARTscore). These are immediately visible as colored frames around each crystallization well image of the inspection program. In addition, regions of droplets with the highest scoring probability found by the system are also available as images.

Surface Roughness Effects on the Vibration Characteristics of AT-Cut Quartz Crystal Plate.

With the miniaturization and high-frequency requirements of quartz crystal sensors, microscopic issues affecting operating performance, e.g., the surface roughness, are receiving more and more attention. In this study, the activity dip caused by surface roughness is revealed, with the physical mechanism clearly demonstrated. Firstly, the surface roughness is considered as a Gaussian distribution, and the mode coupling properties of an AT-cut quartz crystal plate are systematically investigated under different temperature environments with the aid of two-dimensional thermal field equations. The resonant frequency, frequency-temperature curves, and mode shapes of the quartz crystal plate are obtained through the partial differential equation (PDE) module of COMSOL Multiphysics software for free vibration analysis. For forced vibration analysis, the admittance response and phase response curves of quartz crystal plate are calculated via the piezoelectric module. The results from both free and forced vibration analyses demonstrate that surface roughness reduces the resonant frequency of quartz crystal plate. Additionally, mode coupling is more likely to occur in a crystal plate with a surface roughness, leading to activity dip when temperature varies, which decreases the stability of quartz crystal sensors and should be avoided in device fabrication.

Pure- and Pseudo-Lateral-Field-Excitation Characteristics of Relaxor Ferroelectric Single Crystal PMN-PT.

The relaxor ferroelectric single crystal (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT) has high piezoelectric constants, and thus has a good application prospect in the field of highly sensitive piezoelectric sensors. In this paper, for relaxor ferroelectric single crystal PMN-PT, the bulk acoustic wave characteristics on pure- and pseudo-lateral-field-excitation (pure- and pseudo-LFE) modes are investigated. LFE piezoelectric coupling coefficients and acoustic wave phase velocities for PMN-PT crystals in different cuts and electric field directions are calculated. On this basis, the optimal cuts of pure-LFE and pseudo-LFE modes of relaxor ferroelectric single crystal PMN-PT are obtained, namely, (zxt)45° and (zxtl)90°/90°, respectively. Finally, finite element simulations are carried out to verify the cuts of pure-LFE and pseudo-LFE modes. The simulation results show that the PMN-PT acoustic wave devices in pure-LFE mode have good energy-trapping effects. For PMN-PT acoustic wave devices in pseudo-LFE mode, when the device is in air, no obvious energy-trapping emerges; when the water (as a virtual electrode) is added to the surface of the crystal plate, an obvious resonance peak and the energy-trapping effect appears. Therefore, the PMN-PT pure-LFE device is suitable for gas-phase detections. While the PMN-PT pseudo-LFE device is suitable for liquid-phase detections. The above results verify the correctness of the cuts of the two modes. The research results provide an important basis for the development of highly sensitive LFE piezoelectric sensors based on relaxor ferroelectric single crystal PMN-PT.

Ultra-wideband valley transmission on elastic topological phononic crystals

The Valley Hall effect and topological chiral boundary states play a crucial role in investigating elastic wave transmission properties. In this study, to construct the phononic crystal plate structure, periodic scatterer structures are arranged on the bottom plate at a certain thickness. Simulation analysis reveal that modulating the edge states of the designed elastic phononic crystal plate achieves greater degrees of freedom and enhanced backscattering suppression capabilities. Straight boundary, right-angle turning boundary, and valley topological transport with defect and disordered boundary are achieved by utilizing edge states. Experimental validation confirm the robustness against immunodeficiency and holes. The relative width of the topological band gap in the elastic wave system examined in this study exceeds 60%, offering significant advantages and potential for practical applications. This research contributes new insights for engineering applications of ultra-wideband acoustic antennas, acoustic logic control, and other devices.

Low Frequency Attenuation Characteristics of Two-Dimensional Hollow Scatterer Locally Resonant Phonon Crystals.

The finite element method (FEM) was applied to study the low frequency band gap characteristics of a designed phonon crystal plate formed by embedding a hollow lead cylinder coated with silicone rubber into four epoxy resin short connecting plates. The energy band structure, transmission loss and displacement field were analyzed. Compared to the band gap characteristics of three traditional phonon crystal plates, namely, the square connecting plate adhesive structure, embedded structure and fine short connecting plate adhesive structure, the phonon crystal plate of the short connecting plate structure with a wrapping layer was more likely to generate low frequency broadband. The vibration mode of the displacement vector field was observed, and the mechanism of band gap formation was explained based on the spring mass model. By discussing the effects of the width of the connecting plate, the inner and outer radii and height of the scatterer on the first complete band gap, it indicated that the narrower the width of the connecting plate, the smaller the thickness; the smaller the inner radius of the scatterer, the larger the outer radius; and the higher the height, the more conducive it is to the expansion of the band gap.

Protein-to-structure pipeline for ambient-temperature in situ crystallography at VMXi.

The utility of X-ray crystal structures determined under ambient-temperature conditions is becoming increasingly recognized. Such experiments can allow protein dynamics to be characterized and are particularly well suited to challenging protein targets that may form fragile crystals that are difficult to cryo-cool. Room-temperature data collection also enables time-resolved experiments. In contrast to the high-throughput highly automated pipelines for determination of structures at cryogenic temperatures widely available at synchrotron beamlines, room-temperature methodology is less mature. Here, the current status of the fully automated ambient-temperature beamline VMXi at Diamond Light Source is described, and a highly efficient pipeline from protein sample to final multi-crystal data analysis and structure determination is shown. The capability of the pipeline is illustrated using a range of user case studies representing different challenges, and from high and lower symmetry space groups and varied crystal sizes. It is also demonstrated that very rapid structure determination from crystals in situ within crystallization plates is now routine with minimal user intervention.