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Acoustic levitation is widely used in non-container measurement and non-contact manipulation. Particles in the single-axis acoustic levitation are easily unstable in the radial direction under external perturbations. In order to explore the instability in the acoustic levitation during radial perturbations, a nonlinear acoustic levitation model considering the coupling of radial and axial vibration is proposed to analyze the dominant factors influencing the levitation stability, an acoustic levitation system consisting of a transducer and a plane reflector is established, and high-speed photography is used to observe the vibration behavior of the particle with large radial vibration and the levitation stability. The simulation results are compared and verified with the experiments, which indicate that the reduction in axial trapping stiffness due to radial vibration plays a vital role in the levitation instability. The present model can characterize the radial anti-interference ability of different levitators as well as predict the movement trajectories of levitated particles after being disturbed, which is helpful to optimize the design of acoustic levitators and provide guidance for acoustic manipulation. [ABSTRACT FROM AUTHOR]

As the main merits, self-stabilization and no magnetic resistance make the high-temperature superconducting (HTS) magnetic levitation technology a crucial area for high-speed magnetic levitation development. To guarantee a stable operation of superconducting magnetic levitation systems, the dynamic characteristics of superconducting bulk materials occupy a significant place. However, in the previous research, there is still a lack of a simulation method that can describe 6 degree of freedom (DOF) motion of the superconductor. In this paper, an electromagnetic–thermal–dynamic coupling calculation model was established first. Then, the damping characteristics of 5-DOF superconducting levitation were experimentally tested, and the response analysis of the superconductor under 1–20 Hz excitation was carried out to explore the coupled motion relationship between the various degrees of freedom of the superconductor. In addition to the above, the operating conditions and primary resonance intervals that should be avoided by the HTS maglev system were identified. Additionally, a numerical simulation was conducted to investigate the dynamic response of the HTS maglev system under impact loads. All in all, this study explored the temperature rise conditions of superconducting bulk materials under excitation force through magnetic-thermal-force multi-physics coupling research. This 6-DOF model can provide a comprehensive simulation method for superconducting maglev systems in superconductor's motion behavior, attitude, and thermal state monitoring. [ABSTRACT FROM AUTHOR]

Novel transparent glass-ceramics (TGCs) containing cubic α-CaTa 2 O 6 : Ni2+ nanocrystals and their Ni2+ concentration-dependent and temperature-dependent spectroscopic properties were reported. They were obtained from precursor glasses (PGs) with a subsequent heat treatment, in which the PGs of 31CaO-31Ta 2 O 5 -38Al 2 O 3 - x NiO (x = 0.02–1.5 in mol%) were prepared by the aerodynamic levitation technique. A broadband near-infrared (NIR) emission with a full width at half maximum (FWHM) of ∼250 nm was observed at ∼1220 nm under excitation at 980 nm, attributing to the spin-allowed transition of 3T 2g (3F) → 3A 2g (3F) of Ni2+ in octahedral Ta5+ sites in α-CaTa 2 O 6. With the increasing of NiO content, the emission intensity increases at first reaching a maximum at x = 0.3 mol%, and then declines. A red-shifting emission from 1189 to 1258 nm is observed with a broadening FWHM from 218 to 292 nm and a significantly reducing average lifetime from 594.4 to 56.0 μs. When the temperature increased from 298 to 473 K, the emission shows an apparent thermal quenching with a blue shift of 15 nm, where the intensity remained 51 % at 373 K of that at 298 K. Furthermore, it supposes that there are two types of Ni2+ active centers according to the deconvolution of the photoluminescence (PL) spectra, double-exponential fitting of the decay curves and temperature-dependent PL spectra. One shows a stronger concentration quenching, while the other exhibits a more serious thermal quenching. The possible thermal quenching mechanism was also discussed. [ABSTRACT FROM AUTHOR]

Additive manufacturing is critical in modern production with advanced applications across various domains. However, achieving omnidirectional printing that can adapt to varying substrate geometries is still a challenge. Moreover, multi‐material in situ printing without cross‐contamination presents another hurdle. In this study, an acoustophoretic 3D fabrication system capable of omnidirectional and multi‐material in situ 3D printing is reported using acoustic levitation. This system harnesses a phased array of transducers (PAT) to finely tune the ultrasonic field, generating acoustophoretic forces that levitate and transport objects in mid‐air. It allows omnidirectional in situ printing of materials onto complex substrates with diverse orientations in a contactless and voxel‐by‐voxel manner. It is capable of manipulating a broad spectrum of materials, including liquids with zero‐shear viscosities from 1 to 5,000,000 mPa·s, as well as solids. AcoustoFab has successfully printed structural, conductive, and biological materials in varying directions on complex substrates. Additionally, the contactless approach enables in situ printing safely on a delicate surface, as demonstrated by printing on a human hand. The flexibility and versatility of this approach demonstrate promising applications in areas ranging from biomedical engineering to industrial manufacturing. [ABSTRACT FROM AUTHOR]

The magneto‐optical properties of rare‐earth‐rich borate glasses prepared using a levitation technique were thoroughly investigated. Among the series of rare‐earth borate glasses, Tb2O3–B2O3 and Dy2O3–B2O3 glasses displayed remarkably large Faraday effects in the visible region. The Verdet constant of 58Tb2O3–42B2O3 reached −229 rad/T·m at 633 nm, surpassing the value of commercially available single‐crystalline Tb3Ga5O12. Compositions with a higher rare‐earth oxide content (60 mol%) than that of binary glasses facilitated the successful synthesis of Tb2O3–Dy2O3–B2O3 ternary glasses. The Verdet constant linearly increased with increasing Tb2O3 content for the glasses with 40 mol% B2O3. Results indicate that rare‐earth‐rich borate glasses are promising candidates for magneto‐optical applications in the visible region, and that the types and amounts of rare‐earth ion mainly affect these properties. [ABSTRACT FROM AUTHOR]

The distribution of induced current in bulk superconductors plays a crucial role in determining their levitation force and trapped field. To investigate the impact of longitudinally-induced circulation on the magnetic properties of rare-earth barium–copper–oxide (REBCO) bulk superconductors, a single-domain gadolinium–barium–copper–oxide bulk, with a diameter of 30 mm and thickness of 10 mm, was cut horizontally at its semi-height, reaching depths of 0, 5, 10, 15, 20, 25, and 30 mm through a step-cutting method. The bulk's levitation force and trapped field were analyzed in relation to the cutting depth. The results reveal a gradual decrease in both parameters with increasing cutting depth, which can be attributed to the obstruction of longitudinal circulation transmission caused by cutting. This phenomenon has been further elucidated by considering the magnetic characteristics of non-ideal type-II superconductors. Additionally, the local levitation force and trapped field measurements of the bulk further confirmed the conclusion obtained for the bulk considered as a whole. These findings contribute to a better understanding of the magnetic properties of REBCO bulk superconductors. Moreover, this study serves as a valuable reference for future research involving the cutting of bulks, offering significant insights into the practical design of bulk shape and properties through cutting methods. [ABSTRACT FROM AUTHOR]

The most common methodology for performing multiple chemical and biological reactions in parallel is to use microtitre plates with either manual or robotic dispensing of reactants and wash solutions. We envision a paradigm shift where acoustically levitated droplets serve as wells of microtitre plates and are acoustically manipulated to perform chemical and biological reactions in a non-contact fashion. This in turn requires that lines of droplets can be levitated and manipulated simultaneously so that the same operations (merge, mix, and detect) can be performed on them in parallel. However, this has not been demonstrated until this work. Because of the nature of acoustic standing waves, a single focus has more than one trap, and can allow levitation of columns of droplets at the focal point and at half a wavelength above and below that point. Using this approach, we increased the number of acoustically levitated and merged droplets to 6 compared to 2 in the state-of-the-art. We showed that droplets in a column can be moved and merged with droplets in another column simultaneously and in a controlled manner to perform repeats and/or parallelisation of chemical and biological reactions. To demonstrate our approach experimentally, we built an acoustic levitator with top and bottom surfaces made of a 16 × 16 grid of 40 kHz phased array transducers and integrated optical detection system, studied two acoustic trap generation and movement algorithms, and performed an exemplar enzyme assay. This work has made significant steps towards acoustic levitation and manipulation of large numbers of droplets to eventually significantly reduce the use of the current state-of-the-art tools, microtitre plates and robots, for performing parallelised chemical and biological reactions. [ABSTRACT FROM AUTHOR]

Containerless solidification of Al–20wt%Ce is investigated experimentally using the electromagnetic levitation (EML) and impulse atomization (IA) techniques. In the processed EML samples, small primary undercooling and minimal eutectic undercooling are shown. The microstructure consists of large primary Al11Ce3 dendrites surrounded by an α‐Al–Al11Ce3 eutectic. Phase fractions determined by neutron diffraction are similar to the values obtained from a Scheil–Gulliver solidification simulation. Larger IA powders (between 425 and 1000 μm) show a microstructure qualitatively similar to that of EML samples, implying that they follow a similar solidification path. Quantitatively, microstructural features are finer due to the higher cooling rates involved in the solidification process. Atomized particles with a size lower than 425 μm show a strikingly different microstructure, with a very fine eutectic giving way to large intermetallic plates surround by a regular eutectic. Microhardness testing of the structures shows a significant increase in hardness as the sample size decreases, going from 45.8 ± 3.6 HV for the EML sample (lowest cooling rate) to 142.2 ± 12.0 HV for particles in the 106–150 μm range (highest cooling rate). [ABSTRACT FROM AUTHOR]

The radiometric force exerted on a thin perforated membrane and the heat flux from the membrane to a surrounding gas are calculated by the direct simulation Monte Carlo method over wide ranges of the gas rarefaction and membrane porosity. Ab initio potentials are used to model the intermolecular collisions. We find that perforations increase the force several times in the viscous regime of flow but decrease the force in the free-molecular and transitional regimes. The influence of the accommodation coefficients is studied by applying the Cercignani–Lampis model. The effects of gas species, degree of non-equilibrium, and environment temperature are found to have relatively small effects on dimensionless quantities such that the reported results can be applied to wide ranges of these factors and, hence, to numerous practical situations such as the levitation of centimeter-scale membranes at upper atmospheric altitudes. [ABSTRACT FROM AUTHOR]

With the advancement of manufacturing, the precision requirements for various high-precision processing equipment and instruments have further increased. Due to its noncontact nature, simple structure, and controllable performance, electromagnetic levitation has broad application prospects in ultra-precision instruments and ground testing of aerospace equipment. Research on vibration isolation technology using electromagnetic levitation is imperative. This paper reviews the latest research achievements of three types of passive isolators and five active isolation actuators. It also summarizes the current research status of analytical methods for passive isolators and the impact of isolator layout. This study explores current isolators' achievements, such as the development of passive isolators that generate negative stiffness and require mechanical springs for uniaxial translational vibrations, single-function actuators, and control systems focused on position and motion vibration control. Based on the current isolators' characteristics, this review highlights future developments, including focusing on passive isolators for heavy loads and multi-axis isolation, addressing complex vibrations, including rotational ones, and developing methods to calculate forces and torques for arbitrary six-DOF movements while improving speed. Additionally, it emphasizes the importance of multifunctional actuators to simplify system structures and comprehensive control systems that consider more environmental factors. This provides significant reference value for vibration isolation technology using electromagnetic levitation. [ABSTRACT FROM AUTHOR]

The time delay (TD) in the levitation control system significantly affects the dynamic performance of the closed-loop system in electromagnetic suspension (EMS) maglev vehicles. Excessive TD can cause levitation instability, making it essential to explore effective mitigation methods. To address this issue, a Smith Predictor (SP) is integrated into the traditional PID levitation control system. The combination of theoretical analysis and numerical simulation is employed to assess the stability of the time-delay levitation control system after the integration of the Smith Predictor. Theoretical analysis reveals that when TD exceeds a critical threshold, the levitation system becomes unstable. The addition of SP alters the root trajectory of the system characteristic equation from positive to negative, and recovers the levitation system to stable status. Assuming complete knowledge of the dynamic system, the TD compensation value in the SP becomes a key parameter that determines its performance. A minimum effective value (MEV) for TD compensation is identified, correlating with the system's stability region. Under the influence of TD, more complex systems and higher running speeds of the maglev vehicle lead to a narrower stable region and a larger MEV for TD compensation. Given the simulation parameters in this paper, with a system TD of 15 ms and a maximum vehicle speed of 160 km/h, the MEV for TD compensation in the SP should be set at 12 ms. • Smith Predictor is introduced into maglev control system to mitigate the adverse impact from TD. • Analyzed application value of Smith Predictor in levitation control system with time delay. • Provided suggestions for the broader implementation of Smith Predictor in practical engineering. [ABSTRACT FROM AUTHOR]

Magnetic springs, which can be used to replace traditional mechanical springs, have many advantages, such as necessitating no physical contact, generating no friction, no vibration or noise, and having a long lifespan. Nevertheless, their strong nonlinearity limits their widespread application. In this study, we developed a novel permanent magnet spring to address this issue: a Halbach permanent magnetic spring, with a large levitation force and an approximately linear force characteristic curve. First, we introduce the structure and the parameters of the Halbach permanent magnetic spring. Second, we describe the levitation force performance and the stiffness performance of the Halbach permanent magnetic spring using finite element analysis. Third, we analyze the trends through which different parameters influence the levitation force performance and stiffness performance. Finally, we provide recommendations for the future design of and improvement in the Halbach permanent magnetic spring. [ABSTRACT FROM AUTHOR]

Sessile drops are ubiquitous and important in technological applications. While dynamics of liquid drops have been studied under confinement, the possibility of creating sessile drops with reduced dimensionality has not been explored. Here, we demonstrate a quasi-two-dimensional (Q2D) analogy for axisymmetric sessile three-dimensional (3D) drops. The Q2D drops are created by confining liquids between parallel vertical walls, forming low aspect ratio capillary bridges deformed by gravity. Stationary Q2D drops adopt projected shapes analogous to 3D sessile drops, ranging from circular drops to puddles. When moving, the Q2D drops exhibit capillary and fluid mechanical behaviours conceptually analogous to 3D drops, including impacts and sliding. The Q2D drops also exhibit more complex phenomena such as levitation, various instabilities and pattern formation when subjected to external electric, magnetic and flow fields. The 3D-Q2D analogy suggests that the diverse and often complicated phenomena observed in 3D drops can be studied in the simplified Q2D geometry. Additionally, the Q2D confinement analogy allows exploring phenomena arising from the reduced dimensionality and the altered boundary conditions. Axisymmetric sessile liquid drops are everywhere around us and important in numerous technological applications. Here the authors experimentally prepare quasi-two-dimensional sessile drops and show that they display many similar features as the traditional axisymmetric sessile drops, including analogous equilibrium shape, dynamics, and instabilities. [ABSTRACT FROM AUTHOR]

In this study, the microstructure, hardness, density, viscosity, and surface tension of molten pure Ti with TiC particles were studied via electrostatic levitation experiments, where the electrostatic levitation experiment involved container-less processing, which can suppress heterogeneous nucleation via crucibles. Microstructural observation revealed long needle-shaped α-grains across the whole area in the pure Ti sample. On the other hand, smaller needle-shaped α-grains were found in the samples with TiC particles. However, the detailed microstructural analysis of Ti + 0.7vo l%TiC sample revealed that the fine α-grains observed in the Ti + 0.7vo l%TiC are transformed from single grain of prior β phase. This is because the TiC particles dissolve into the molten Ti during the electrostatic levitation experiment. Instead, Ti–rich TiC precipitates formed by cooling can act as pinning sites rather than heterogeneous nucleation sites, which results in a finer microstructure for the samples with TiC particles during the electrostatic levitation experiment. The density of the samples is linearly related to the temperature, and it decreases with increasing temperature. In addition, a higher density is observed for the samples with TiC particles. Although linear relationships between the surface tension and temperature were found, the addition of TiC particles had no notable effect on the viscosity of the molten pure Ti. [ABSTRACT FROM AUTHOR]

The levitation of Leidenfrost droplets on liquid pool is fascinating, but its final stage is lack of understanding. Here, we found that a droplet levitated on liquid layer eventually deviated from Leidenfrost state once its radius was lower than a critical radius due to evaporation. The critical radius of ethanol droplet deviated from Leidenfrost state on silicone oils with a thickness ranging from 2.0 to 15.0 mm was determined by experiment. The influences of the initial radius of droplet, viscosity, and thickness of liquid layer on critical radius were analyzed. In addition, the critical radius decreases with increase in superheat for ΔT lower than 25.0 °C, whereas it does not significantly vary after ΔT exceeding 25.0 °C. The bottom temperature Tb of droplet does not approach to saturation temperature even under a high superheat. The experiment found that Marangoni convection existed inside droplet. Based on a theoretical model considering Marangoni convection, the reason for droplet deviated from Leidenfrost state was explained. These findings are helpful for understanding the final state of Leidenfrost droplet on liquid layer and would provide a potential practical application such as extinction of oil pool fires with liquids. [ABSTRACT FROM AUTHOR]

In this study, the effect of the pre-infiltration temperature (Ti) on the liquid-phase infiltration characteristics and its effect on the magnetic properties of single-domain GdBCO bulks prepared by the top-seeded infiltration growth (TSIG) method are comprehensively investigated. The results reveal that (1) the liquid Ba-Cu-O phase (LP) did not uniformly infiltrate into the Gd2BaCuO5 (Gd-211) solid-phase pellet (SPP). (2) The initial melting and infiltration of the LP occurred at approximately 920 °C. The average infiltration depth and amount of LP that infiltrated the SPP increased with increasing Ti accompanied by the shrinkage and depletion of the LP pellet. (3) The LP penetrated up to the top surface of the SPP and uniformly infiltrated throughout the SPP when the Ti was approximately 960 °C and 1020 °C, respectively. (4) The mean Gd-211 particle size of the pre-infiltrated SPP increased from 1.94 µm at 920 °C to 2.52 µm at 1040 °C as the Ti rose. (5) The magnetic properties and microstructure of the single-domain GdBCO bulks were significantly influenced by the microstructure of the pre-infiltrated SPP. The largest levitation force of 35.64 N and trapped field of 0.23 T were obtained in the single-domain GdBCO bulks at an infiltration Ti of 960 °C. [ABSTRACT FROM AUTHOR]

We present the levitation and residing at particular places of human breast cancer (T47D) cells on a magnetic microsystem quickly fabricated by printing. The microsystem consists of arrays of soft magnetic elements and is put adjacent to a bulk magnet. Under a magnetic field generated by the magnet, elements are magnetized, obtaining a significant magnetic field strength and a high magnetic field gradient in the micro-space above them. The field applies a magnetic force on the cells as they are dropped to the surfaces of the elements. As a result, levitation and a stable position for each cell are observed. The levitation and position of a cell can be predicted by a theory that takes into account the magnetic, buoyant, and gravitational forces on the cells. Our theoretical and experimental results agree well with one another, and the microsystem is capable of efficient cell manipulation. [ABSTRACT FROM AUTHOR]

It is widely recognized that the application of nanoparticles has the potential to improve the dielectric properties of transformer oil. Nevertheless, there is a scarcity of studies that have utilized pure nanofluids, and in practical applications, it is inevitable for transformer oil to become contaminated. Therefore, this study conducted tests to investigate how the shape and size of metal contaminants impact the dielectric performance of Fe3O4 nanofluids. The findings from the levitation voltage test indicate that as the size and diameter of the particle increase, the levitation voltage value measured also increases, and conversely. Moreover, a higher concentration of nanoparticles leads to a higher measured levitation voltage value. On the other hand, the breakdown voltage test results demonstrate that larger and sharper particles result in lower measured breakdown voltage values, and vice versa. The simulation outcomes regarding electric field distribution reveal that larger and sharper particles correspond to higher measured electric field values, while the opposite is true for smaller and less sharp particles. [ABSTRACT FROM AUTHOR]

When a YBaCuO bulk superconductor (SC) is subdivided, its levitation force may not be significantly reduced after this partitioning process. The force will decrease even less if the sectional surface introduced by partitioning is parallel to the induced current loop. Moreover, the levitation force can be maintained because the partitioning makes the SC more magnetizable. These findings have implications for longitudinal maglev technology. A method for calculating levitation forces in nonuniform fields based on critical-state theory is proposed. In this method, an SC is divided into several regions where the external field is approximately uniform within each subvolume. To minimize the force degradation introduced by partitioning, the cutting surfaces should be parallel to the induced current. This approximate approach can effectively reproduce the experiment and improve the calculation accuracy. Another application of combining and recovering discrete SCs is demonstrated, and it is shown that a recombined SC according to the small-loss partitioning condition can achieve 68% of the levitation capacity of an intact sample. In addition, the invisible cracks inside the bulk sample can be predicted by comparing its levitation force with that of the intact sample. [ABSTRACT FROM AUTHOR]

Acoustic levitation is the only method capable of suspending samples with different material properties and geometries, even in the liquid phase. Despite its widespread applications, droplet levitation still has a problem controlling the droplet’s position due to initial oscillations before reaching stability. This research investigates the effects of droplet physical properties, such as viscosity, radius, and density, on droplet oscillation amplitude. For this purpose, numerical simulations that apply the effect of the mentioned properties with acceptable accuracy and precision results were conducted using COMSOL Multiphysics 6.1 commercial software. The unique feature of using a simulation is the ability to study the effect of each parameter independently from the rest of the properties, which is not directly possible in experimental tests. The results emphasize the direct influence of viscosity on droplet oscillation amplitude. They also demonstrated that elevated viscosity leads to a decrease in droplet oscillation amplitude. In addition, increasing the density because of the added weight decreases the droplet amplitude. The droplet radius effect is more complicated because it is associated with two opposite effects. Increased droplet radius has the same effect as viscosity because of weight addition. On the other hand, a larger droplet's radius enlarges the cross-section and leads to a weak increase in droplet amplitude.

Acoustic levitation is an attractive and versatile technique that offers several advantages in terms of particle size, range, reconfigurability, and ease of use with respect to alternative levitating techniques. In this paper, we study the use of active damping to improve the response time and positioning precision of an acoustic levitator operating in air. We use a laser Doppler vibrometer to measure the velocity of a levitated particle. Using this information, a control algorithm is designed and implemented to provide active damping. By system identification and modeling, we demonstrate that the active damper mechanism is well-predictable by models and can be electronically reconfigured and controlled. [ABSTRACT FROM AUTHOR]

Maglev vehicles apply the entire vehicle load uniformly onto bridges through levitation forces. In assessing the dynamic characteristics of the maglev train–bridge coupling system, it is reasonable to simplify the distributed levitation force as a concentrated force. This article theoretically derives the analytical response of bridge dynamics under the action of a single constant force and conducts numerical simulations for a moving single constant force and a series of equally spaced constant forces passing over simply supported beams and two-span continuous beams, respectively. The topic of discussion is the response of bridge dynamics when different degrees of force concentration are involved. High-precision displacement and acceleration sensors were utilized to conduct tests on the Shanghai maglev line to verify the accuracy of the simulation results. The results indicate that when simplifying the distributed levitation force into a concentrated force model, a frequency ratio can be used to analyze the conditions for resonance between the train and the bridge and to calculate the critical speed of the train; the levitation distribution force of a high-speed maglev vehicle can be simplified into four groups of concentrated forces based on the number of levitation frames to achieve sufficient accuracy, with the dynamic response of the bridge being close to that under distributed loads. [ABSTRACT FROM AUTHOR]

Magnetic suspension balance systems (MSBSs) need to allow vehicle models to levitate stably in different attitudes, so it is difficult to ensure the stable performance of the system under different levitation gaps using a controller designed with single balance point linearization. In this paper, a levitation controller based on linear model predictive control and a back-propagation neural network (LMPC-BP) is proposed and simulated for single-point magnetic levitation. The deviation of the BP network is observed and compensated by an expansion state observer (ESO). The iterative BP neural network model is further updated using current data and feedback data from the ESO, and then the performance of the LMPC-BP controller is evaluated before and after the update. The simulation results show that the LMPC-BP controller can achieve stable levitation at different gaps of the single-point magnetic levitation system. With further updating and iteration of the BP network, the controller anti-jamming performance is improved. [ABSTRACT FROM AUTHOR]

Acoustic levitation is an interesting technique used for levitating small objects/materials using sound waves. In this study, lateral movement of levitating particles is demonstrated experimentally and numerically. The method can simultaneously move multiple particles and the paper demonstrates levitation for three particles. Initially, an ultrasonic tweezer with a resonance frequency of 40 kHz is used to levitate three particles of average weight of 0.15 mg each. The experimental design is based on numerical simulation. Further, the levitated particles are moved in a lateral direction using two ultrasonic tweezers setup by manipulating the phase of one of the tweezers using Arduino Nano. As evident by simulations, the movement takes place due to the interference of waves leading to the movement of pressure node. The lateral movement of particles can be controlled and even reversed by changing the phase difference. [ABSTRACT FROM AUTHOR]

Electromagnetic levitation (EML) is a promising technique allowing to melt various materials, including refractive metals, while avoiding physical contact between the molten material and components of the melting system, thus avoiding contamination of the molten material. EML coils act both as a container and a heating source for a conductive sample placed within it. EML systems are difficult to optimize for specific tasks and computational simulations are often used to aid the process. Development of simulations of EML processes is an ongoing field of research. Obtaining precise experimental measurement data of EML processes is important for development and verification of computational simulations. This study aims to provide experimental data of simultaneous measurements for magnetic field, Joule heating and lift force in different conical EML coils with a counterturn. [ABSTRACT FROM AUTHOR]

Near-field ultrasonic levitation (NFUL) technology is increasingly attracting attention for its advantages of non-contact nature, compactness, and environmental friendliness. Nevertheless, the development of NFUL is hindered by challenges such as carrying capacity and stability. To date, most studies have focused on the static stability of NFUL, primarily through analysis of the restoring force. However, there remains a significant gap in the literature regarding the motion prediction of levitated objects, which is the focus of this paper. A numerical model coupling the levitated object and the squeeze film is established, and then, the Reynolds equation considering the motion parameters of the levitator is derived. Since the misalignment and inclination of the levitator are concurrent cases, its inclination needs to be considered in the film thickness expression. Subsequently, due to the introduction of an imaginary levitator with a groove, the eight-point discrete method is applied to solve the discontinuous film thickness problem. Thereupon, the pressure profile is obtained by determining the inclination angle of the levitator using the spline interpolation. The motion trajectory and frequency of the levitator are estimated utilizing the time-marching method and corroborated through experimental measurements. Both numerical and experimental results indicate that the motion frequency initially increases sharply with rising the preset eccentricity, before gradually diminishing. Additionally, higher motion frequencies are observed at larger amplitudes of the vibrator and lower weights of the levitator. Comparatively, the motion frequency of a levitator under a flexible vibrator is also found to be higher than that under a rigid vibrator. [ABSTRACT FROM AUTHOR]

To understand the effects of convection and a temperature gradient on solidification behavior, Ti–6Al–4V alloy samples were melted and solidified using three levitation methods: electrostatic levitation (ESL), electromagnetic levitation (EML) with severe convection, and aerodynamic levitation (ADL) with a large temperature gradient. Titanium carbide (TiC) particles were added to Ti–6Al–4V as heterogeneous nucleation site particles to make differences in microstructures obvious. The cross sections of the levitated samples were analyzed using electron backscatter diffraction (EBSD) to obtain prior-β grain maps. The grains in the ESL sample were relatively isotropic in shape, whereas the grains and dendrite structures of the EML sample were radially arranged throughout the cross section. Therefore, under significant convection, such as in the EML sample, as grain growth is suppressed downstream, grain growth in the direction perpendicular to the melt flow is accelerated. In the ADL sample with a large temperature gradient in a vertical direction, columnar and equiaxed grains were formed in the lower and upper parts of the sample, respectively. Therefore, during unidirectional solidification due to a large temperature gradient, the shape of the grains changes from columnar to equiaxed as constitutional undercooling increases. [ABSTRACT FROM AUTHOR]

Clarifying the dissolution behavior of titanium carbide (TiC) during heating is crucial for establishing suitable heating conditions for prior-β grain refinement of Ti–6Al–4V induced by TiC particles. This study aims to reveal the effects of heating in the electrostatic levitation (ESL) experiments on the dissolution of TiC by establishing the dissolution kinetics of TiC in liquid Ti–6Al–4V. The sintered mixture of Ti–6Al–4V powder and TiC particles was melted and solidified in ESL. The integral value of heating, I (T, t), with the temperature and heating time serves as a valuable index of the amount of heating. The amount of residual TiC, MR, decreases exponentially with the increase of I (T, t), indicating the symmetry of the Johnson–Mehl–Avrami–Kolmogorov equation. A phase field simulation of TiC dissolution revealed that the dissolution time increases in proportion to the 1.8th power of the initial particle diameter. Additionally, the value of MR calculated using the dissolution equation based on the diffusion theory was consistent with the results of the ESL experiments at a diffusion coefficient, D, of about 1 – 3 × 10−11 m2 s−1, which is an intermediate value of D in multiple diffusion forms. The dissolution model also estimates the number of TiC particles which work as the nucleation sites (Active-TiC). [ABSTRACT FROM AUTHOR]

Electroadhesive forces are crucial in various applications, including grasping devices, electro-sticky boards, electrostatic levitation, and climbing robots. However, the design of electroadhesive devices relies on speculative or empirical error approaches. Therefore, we present a theoretical model comprising predictive coplanar electrodes and protective layers for analyzing the electrostatic fields between an object and electroadhesive device. The model considers the role of protective layer and the air gap between the electrode surface and the object. To exert a higher electroadhesive force, the higher permeability of the protective layer is required. However, a high permeability of the protective layer is hard to withstand high applied voltage. To overcome this, two materials with different permeabilities were employed as protective layers—a low-permeability inner layer and a high-permeability outer layer—to maintain a high voltage and generate a large electroadhesive force. Because a low-permeability inner layer material was selected, a more permeable outer layer material was considered. A theoretical analysis revealed complex relationships between various design parameters. The impact of key design parameters and working environments on the electroadhesion behavior was further investigated. This study reveals the fundamental principles of electroadhesion and proposes prospective methods to enhance the design of electroadhesive devices for various engineering applications. [ABSTRACT FROM AUTHOR]

Both density and surface tension were systematically investigated over a wide temperature and compositional range for the liquid Al–V alloy system. The thermophysical properties were measured in an electromagnetic levitation device. A linear decrease in surface tension and density with increasing temperature was observed for every alloy composition investigated. Additionally, a decrease in density and surface tension was observed for increasing aluminum content among the different probed samples. This decrease is, a strong deviation from an ideal mixing behavior which was experienced for both properties. Different models, including variants of the well-established Butler model, were employed to better describe the compositional dependence of density and surface tension in the liquid Al–V system. The advantages and disadvantages were discussed for each model describing the measured thermophysical property data. Strong similarities were observed when comparing the mixing behavior and segregation effects of the investigated Al–V system with already established works for the liquid Al–Ti system. The results suggest that both vanadium and titanium show similar mixing behavior when alloyed with aluminum. [ABSTRACT FROM AUTHOR]

This study employs the transmitter part of an ultrasonic proximity sensor to generate a powerful ultrasonic field for medical humidification. This field is created using an arrangement of small ultrasonic transmitter transducers configured in an acoustic levitator-style setup. As droplets pass through this ultrasonic field, they undergo disintegration, leading to an accelerated evaporation process. The research findings highlight a significant change in droplet size distribution due to ultrasonics, resulting in a notable increase in the rate of evaporation. As a result, this study presents a conceptual framework for reimagining humidification devices for lung therapeutic purposes through the utilization of simple sensor technology. [ABSTRACT FROM AUTHOR]

To reduce the vehicle-bridge coupled vibration of a new-type maglev vehicle with mid-mounted suspension (MVMS) on a curve and increase its curve-passing speed, the forced guidance device (FGD) for MVMS is designed and the effectiveness of the FGD is proved. Firstly, on the basis of the FGD for HSST (High Speed Surface Transport) maglev vehicle and the geometric relationship between the movable sliders and the cabin as MVMS passes through a curved track, the FGD scheme for MVMS was designed. Secondly, the dynamic models with 5-bogies MVMSs (with and without FGD), control system, 11 flexible bridges, and track irregularities were established. Finally, the vehicle-bridge coupled vibration response of MVMSs on the curved track was analysed. Results show that the accelerations of the bridges, levitation modules, and cabin can be reduced significantly by installing FGD, especially at higher speeds. Compared to the accelerations without FGD, the maximum lateral and vertical accelerations of each bridge midspan can be reduced respectively by 56% and 43% at the speed of 45 km/h, those of the levitation modules can be reduced by 48% and 90%, respectively, and those of the cabin can be reduced by 37% and 53%, respectively. [ABSTRACT FROM AUTHOR]

Electromagnetic levitation (EML) is a good method for high-temperature processing of reactive materials such as titanium–aluminum (Ti–Al) alloys. In this study, the oscillation and deformation processes of Ti-48Al-2Cr alloy specimens at different high-frequency currents during the EML process were simulated using the Finite Element Method and Arbitrary Lagrangian–Eulerian (ALE) methods. The data of oscillation, stabilization time, deformation, and distribution of electromagnetic–thermal–fluid fields were finally obtained. The accuracy of the simulation results was verified by EML experiments. The results show the following: the strength and distribution of the induced magnetic field inside the molten droplet are determined by the high-frequency current; under the coupling effect of the electromagnetic field, thermal field, and fluid field, the temperature rise of electromagnetic heating is rapid, and accompanied by strong stirring, resulting in a uniform distribution of the internal temperature and a small temperature difference. Under the joint action of gravity and Lorentz force, the molten droplets are first within a damped oscillation and then tend to stabilize with time, and finally maintain the "near rhombus" shape. [ABSTRACT FROM AUTHOR]

In this research, a novel method to improve the particle size and content of Y2BaCuO5 (Y-211) in YBa2Cu3O7 − x (YBCO) bulks was demonstrated. The single-domain YBCO bulks (20 mm in diameter) have been fabricated employing the RE+011 TSIG technique with different heating rates during the liquid phase infiltration (LPI) stage. The various heating rates on Y-211 size and its content in the final YBCO samples has been investigated in detail. The findings suggest that the average size of the Y-211 particles in the Y-123 matrix initially decreases followed by an increase, while its volume fraction gradually decreases with increasing heating rate. Furthermore, it is observed that the levitation force and the trapped fields exhibit an initial increase followed by a subsequent decrease as the heating rate increases. Among all the samples, sample S3 (heating rate of 30 °C/h) has the best magnetic levitation force and trapped field performances at 77 K, i.e., the largest values are of 45.3 N and 0.41 T, respectively. The results suggest that, while employing the RE+011 TSIG technique for YBCO bulk fabrication, the average size and volume fraction of Y-211 particles in the final sample can be further enhanced by controlling the heating rates during the LPI stage, obviating any need for chemical refining agents. [ABSTRACT FROM AUTHOR]

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The viscous friction of a ferrofluid in the coaxial gap between a stationary outer nonmagnetic tube and a uniformly and rectilinearly moving inner cylindrical permanent magnet was investigated experimentally and theoretically. An analytical expression for the effective coefficient of friction was proposed within the framework of the model concepts of the Couette–Poiseuille flow profile with zero flow rate and was confirmed in a laboratory experiment. [ABSTRACT FROM AUTHOR]

Varying the chemical consistency of acoustically levitated droplets opens up an in situ study of chemical and biochemical reactions in small volumes. However, the optimization of the mixing time and the minimization of the positional instability induced by solution dispensing are necessary for practical applications such as the study of the transient state of macromolecules crystallography during the ligand binding processes. For this purpose, we study the inertial mixing in a configuration compatible with the room‐temperature crystallography using the acoustic levitation diffractometer, therein solution drops ejected at high velocity collide and coalesce with droplets dispensed on acoustically levitated and rotating polymer thin‐film sample holders. With the proposed method, we are able to achieve the mixing time of ∼0.1 s for sub‐micro and a few microliter droplets. The observed short mixing time is ascribed to the rapid penetration of the solution into the droplets and confirmed by a computational fluid dynamic simulation. The demonstrated accelerated solution mixing is tested in a pilot time‐lapse protein crystallography experiment using the acoustic levitation diffractometer. The results indicate the detection of transient ligand binding state within 2 s after the solution dispensing, suggesting the feasibility of the proposed method for studying slow biochemical processes. [ABSTRACT FROM AUTHOR]

This paper presents a study on a push-down electromagnetic levitation system designed for suspending an object, counteracting gravity. The object is embedded with a magnet that allows its support using the electromagnetic levitation system. It involves a coupled electromagnetic field problem with a mechanical problem. Improving the levitation force and increasing the distance between the emitter and reflector are necessary for the correct positioning of the object. This paper proposes the use of a standing wave levitator to suspend and maintain a certain distance for an object using the electromagnetic levitation state.

Rare earth and barium titanates are useful as ferroelectric, dielectric, and optical materials. Measurements of their thermophysical properties in the liquid state can help guide melt processing technologies for their manufacture and advance understanding of fragile liquids' behavior and glass formation. Here, we report the density, thermal expansion, viscosity, and surface tension of molten BaTi2O5, BaTi4O9, and 83TiO2-17RE2O3 (RE = La or Nd). Measurements were made using electrostatic levitation and droplet oscillation techniques in microgravity, which provide access to quiescent liquid droplets and deep supercooling of 510–815 K below the equilibrium melting points. Densities were measured over 900–2400 K. Viscosities were similar for all four compositions, increasing from ∼10 mPa s near 2100 K to ∼30 mPa s near 1750 K. Surface tensions were 450–490 dyn cm−1 for the rare earth titanates and 383–395 dyn cm−1 for the barium titanates; surface tensions of all compositions had small or negligible temperature dependence over 1700–2200 K. For solids recovered after melt quenching, x-ray microtomography revealed the fracture mechanics in crystalline products and minimal internal porosity in glass products, likely arising from entrapped gas bubbles. Internal microstructures were generally similar for products processed either in microgravity or in a terrestrial aerodynamic levitator. [ABSTRACT FROM AUTHOR]

In this study, we have developed an electrostatically suspended accelerometer (ESA) specifically designed for ground use. To ensure sufficient overload capacity and minimize noise resulting from high suspension voltage, we introduced a proof mass design featuring a hollow, thin-walled cylinder with a thin flange fixed at the center, offering the highest surface-area-to-mass ratio compared to various typical proof mass structures. Preload voltage is directly applied to the proof mass via a golden wire, effectively reducing the maximum supply voltage for suspension. The arrangement of suspension electrodes, offering five degrees of freedom and minimizing cross-talk, was designed to prioritize simplicity and maximize the utilization of electrode area for suspension purposes. The displacement detection and electrostatic suspension force were accurately modeled based on the structure. A controller incorporating an inverse winding mechanism was developed and simulated using Simulink. The simulation results unequivocally demonstrate the successful completion of the stable initial levitation process and suspension under ± 1 g overload. [ABSTRACT FROM AUTHOR]

The work examines the main technical indicators of electromechanical converters callers with levitation elements, a generalized design method has been developed tions, as well as design diagrams and functional dependencies of the main varieties of electromechanical devices with elements of levitation. Analytical expressions for the levitation coefficient as a function of the dimensions of the magnetic core and coefficient factor of force multiplicity, technical characteristics of levitation material element, set superheat temperature. A mathematical model has been compiled for based on the parameters of the current mode and forces from the equations of electrical, magnetic, mechanical and thermal circuits of the magnetic system. As a result, the main dimensions of the magnetic system and dimensionless quantities. Analytic expressions for the main dimensions, the specified values of the winding overheating temperature are taken into account, input and output parameters, the condition of uniformity of the magnetic field in the working air nom gap. The optimal values of the dimensions of the magnetic circuit, active resistors have been determined winding voltages are minimal, resulting in minimization of losses active capacities. [ABSTRACT FROM AUTHOR]

Acoustic levitation can provide significant benefits for many fundamental research questions. However, it is important to consider that the acoustic field influences the measurement environment. This work focuses on the dissolution of immobilised drops using acoustic levitation in liquid–liquid systems. Previous work demonstrated that the acoustic field of standing waves impacts mass transfer by affecting the spread of dissolved substances in the continuous phase in two distinct ways: (I) solutes may either pass through nodal planes of the standing waves or (II) not pass. The binary systems examined for case (I) are 1-hexanol–water and 1-butanol–water, and for case (II), n-butyl acetate–water and toluene–water. This work quantifies the intensification effect of acoustic levitation on dissolution for the two types of behaviour, by comparing them with reference measurements of mechanically attached dissolving drops. The system was designed to ensure minimal intensification. The minimum intensification of mass transfer for levitating drops in the used setup of case (I) was 25%, and for case (II), it was 65%, both increasing with decreasing surface-equivalent diameter. With this understanding, acoustic levitation can be used more accurately in the field of mass transfer studies. [ABSTRACT FROM AUTHOR]

This paper analyzes the viability of different solutions to passively augment the axial stiffness of a horizontal axis radial levitation passive magnetic bearing (PMB) with a previously studied topology. The zero-field cooling (ZFC) of high-temperature superconductor (HTS) bulks promotes higher magnetic impulsion and levitation forces and lower electromagnetic losses than those with field-cooling (FC) but, on the other hand, the guiding stability is much lower than those with FC. Because of stability reasons, FC was adopted in most superconducting maglev systems. The trend of this research group has been to develop a horizontal axis HTS ZFC radial levitation PMB presenting notable levitation forces with reduced electromagnetic losses, defined by a topology that creates guiding stability. Previous work has shown that optimizing the bearing geometry to maximize magnetic guidance forces might not be enough to guarantee the axial stiffness required for many applications. First, the extent to which guidance forces are augmented by increasing the number of HTS bulks in the stator is evaluated. Then, the axial stiffness augmentation by passively adding two limiting permanent magnet (PM) rings is evaluated. The results show that the axial stiffness is highly augmented by adding limiting PM rings with no significant additional investment. This change enables the use of the studied ZFC superconducting PMB in high-precision axial stability applications, such as precision gyroscopes, horizontal axis propellers, and turbines. [ABSTRACT FROM AUTHOR]

The crystallization of paramagnetic species in a magnetic field gradient under microgravity-like conditions is an area of interest for both fundamental and applied science. In this paper, a setup for the crystallization of paramagnetic species in the magnetic field up to 7 T generated by a superconducting magnet is described. The research includes calculations of the conditions necessary to compensate for the gravitational force for several types of paramagnetic substances using the magnetic field of superconducting magnets (4.7 T, 7 T, 9.4 T, and 16.4 T). Additionally, for the first time, the crystallization of copper sulfate and cobalt sulfate, as well as a mixture of copper sulfate and cobalt sulfate under gravitational force compensation in a superconducting magnet, was performed. This paper experimentally demonstrates the feasibility of growing paramagnetic crystals within the volume of a test tube on the example of copper and cobalt sulfate crystals. A comparison of crystals grown from the solution of a mixture of copper and cobalt sulfates under the same conditions, with and without the presence of a magnetic field, showed changes in both the number and size of crystals. [ABSTRACT FROM AUTHOR]

Controllably regulating the electrostatic bilayer of nanogold colloids is a significant premise for synthesizing spherical nucleic acid (SNA) and building ordered plasmonic architectures. We develop a facile acoustic levitation reactor to universally synthesize SNAs with an ultra‐high density of DNA strands, which is even higher than those of various state‐of‐the‐art methods. Results reveal a new mechanism of DNA grafting via acoustic wave that can reconfigure the ligands on colloidal surfaces. The acoustic levitation reactor enables substrate‐free three‐dimentional (3D) spatial assembly of SNAs with controllable interparticle nanogaps through regulating DNA lengths. This kind of architecture may overcome the plasmonic enhancement limits by blocking electron tunneling and breaking electrostatic shielding in dried aggregations. Finite element simulations support the architecture with 3D spatial plasmonic hotspot matrix, and its ultrahigh surface‐enhanced Raman scattering (SERS) capability is evidenced by in situ untargeted tracking of biomolecular events during photothermal stimulation (PTS)‐induced cell death process. For biomarker diagnosis, the conjugation of adenosine triphosphate (ATP) aptamer onto SNAs enables in situ targeted tracking of ATP during PTS‐induced cell death process. Particularly, the CD71 receptor and integrin α3β1 protein on PL45 cell membrance could be well distinguished by label‐free SERS fingerprints when using specific XQ‐2d and DML‐7 aptamers, respectively, to synthesize SNA architectures. Our current acoustic levitation reactor offers a new method for synthesizing SNAs and enables both targeted and untargeted SERS analysis for tracking molecular events in living systems. It promises great potentials in biochemical synthesis and sensing in future. [ABSTRACT FROM AUTHOR]

A body immersed in a supersaturated fluid like carbonated water can accumulate a dynamic field of bubbles upon its surface. If the body is mobile, the attached bubbles can lift it upward against gravity, but a fluid-air interface can clean the surface of these lifting agents and the body may plummet. The process then begins anew, and continues for as long as the concentration of gas in the fluid supports it. In this work, experiments using fixed and free immersed bodies reveal fundamental features of force development and gas escape. A continuum model which incorporates the dynamics of a surface buoyancy field is used to predict the ranges of body mass and size, and fluid properties, for which the system is most dynamic, and those for which body excursions are suppressed. Simulations are then used to probe systems which are dominated by a small number of large bubbles. Body rotations at the surface are critical for driving periodic vertical motions of large bodies, which in turn can produce body wobbling, rolling, and damped surface 'bouncing' dynamics. When a solid object is placed in a supersaturated environment, it can exhibit interesting dynamics. Spagnolie et al. conducted an experiment using raisins and 3D-printed bodies in carbonated water and found that the motion of the solid object is influenced by the accumulation and release of bubbles as they reach the surface. [ABSTRACT FROM AUTHOR]