Levitation Of Objects Research Articles

Using an electrically charged mist to visualize the potential wells in “sonomaglev,” a combined diamagnetic-acoustic levitator

We use a water mist to experimentally visualize the wells in the potential energy of material levitated by a combined diamagnetic-acoustic levitator. The levitator consists of an 18.5 T superconducting magnet, which can levitate diamagnetic material, such as water, plastics, and organic materials, by applying a magnetic body force counteracting the force of gravity. Low-power ultrasound transducers operated at 37.5 kHz generate an acoustic field that spatially modulates the net force acting on the diamagnetically levitated material, making “sonomaglev” capable of levitating multiple objects in stable equilibrium. In these experiments, we levitate a mist of water droplets that are electrically charged so that they repel each other, preventing them from coalescing as a single drop in each of the local potential minima. The shapes of the potential wells are revealed by the shapes of clusters of droplets, which conform to the isosurfaces of the sum of the magnetic, gravitational, and acoustic potentials. The spacing of the droplets in a cluster is shown to depend on their charge, volume, and the force constant of the well in a simple model. Compared to acoustic levitation alone, the combination of diamagnetic and acoustic levitation allows more scope for the manipulation of levitated objects, since the acoustic field is not constrained by the requirement to balance the force of gravity. The method demonstrated here allows the influence on the potential energy of switching on the acoustic field to be observed directly.

Characterization of a levitated sub-milligram ferromagnetic cube in a planar alternating-current magnetic Paul trap

Microscopic levitated objects are a promising platform for inertial sensing, testing gravity at small scales, optomechanics in the quantum regime, and large-mass superpositions. However, existing levitation techniques harnessing optical and electrical fields suffer from noise induced by elevated internal temperatures and charge noise, respectively. Meissner-based magnetic levitation circumvents both sources of decoherence but requires cryogenic environments. Here, we characterize a sub-milligram ferromagnetic cube levitated in an alternating-current planar magnetic Paul trap at room temperature. We show behavior in line with the Mathieu equations and quality factors of up to 2500 for the librational modes. Besides technological sensing applications, this technique sets out a path for megahertz librational modes in the micrometer-sized particle limit and can be extended by implementing superconducting traps in cryogenic environments, allowing for magnetic coupling to superconducting circuits and spin-based quantum systems.

Direct measurement of forces in air-based acoustic levitation systems.

Acoustic levitation is frequently used for non-contact manipulation of objects and to study the impact of microgravity on physical and biological processes. While the force field produced by sound pressure lifts particles against gravity (primary acoustic force), multiple levitating objects in the same acoustic cavity interact via forces that arise from scattered sound (secondary acoustic forces). Current experimental techniques for obtaining these force fields are not well-suited for mapping the primary force field at high spatial resolution and cannot directly measure the secondary scattering force. Here, we introduce a method that can measure both acoustic forces in situ, including secondary forces in the near-field limit between arbitrarily shaped, closely spaced objects. Operating similarly to an atomic force microscope, the method inserts into the acoustic cavity a suitably shaped probe tip at the end of a long, flexible cantilever and optically detects its deflection. This makes it possible to measure forces with a resolution better than 50 nN and also to apply stress or strain in a controlled manner to manipulate levitated objects. We demonstrate this by extracting the acoustic potential present in a levitation cavity, directly measuring the acoustic scattering force between two objects, and applying tension to a levitated granular raft of acoustically bound particles in order to obtain the force-displacement curve for its deformation.

Customized and high-performing acoustic levitators for contact-free experiments

Acoustic levitators are becoming increasingly common research instrumentation for contact-free, lab-in-a-droplet studies. Recently, levitators that employ multiple, small, ultrasonic transducers have gained popularity, given their low price, temperature and spatial stability, low voltage, and accessibility. Yet, the current state-of-the-art device, TinyLev, presents limitations for certain applications in terms of stability, strength, and compactness. Herein, we developed three new levitators and evaluated the effect of the construction parameters (e.g., distance of opposing arrays, number and arrangement of transducers, etc.) on their performance. The best performing levitator from this work had half the number of transducers, compared to TinyLev, though presented 1.7 and 3.5 times higher levitation capacity along the horizontal and vertical configurations, respectively, and 4.7 and 2.0 times higher horizontal and vertical stability of a levitated object, respectively. Additionally, we present a direct means to evaluate the acoustic radiation net force acting on a deformable object for uniaxial levitators, without the use of a microphone or a schlieren deflectometer for this type of levitators. The theoretical and experimental observations provide insights for adapting the acoustic levitator design for specific applications. Finally, we developed an open-source software which allows the evaluation of the acoustic pressure field generated by customized designs and provides the necessary files for 3D printing the scaffold of the levitator. This study aims to increase accessibility and promote further developments in contact-free experiments.

Magnetic levitation of nanoscale materials: the critical role of effective density

The magnetic levitation (MagLev) of diamagnetic materials in a paramagnetic solution is a robust technique for the density-based separation, measurements, and analysis of bulk materials/objects (e.g., beads and plastics). There is a debate in the literature, however, about whether a MagLev technique is reliable for the separation and/or density measurements of nanoscale objects. Here, we show that MagLev can levitate nanoparticles; however, the transition from the bulk to an ‘effective’ density must be acknowledged and considered in density measurements at the nanoscale regime. We performed a proof-of-concept study on MagLev’s capability in measuring the ‘effective density’ of multiscale silver particles (i.e. microparticles, nanopowder, and nanoemulsion). In addition, we probed the effective density of nanoscale biomolecules (e.g. lipoproteins) using a standard MagLev system. Our findings reveal that the MagLev technique has the capability to measure both bulk density (which is independent of the size and dimension of the material) and the effective density (which takes place at the nanoscale regime and is dependent on the size and surrounding paramagnetic solution) of the levitated objects.

Investigation of the non-contact flip motion of a planar levitated object using the acoustic jumping phenomenon

Investigation of the non-contact flip motion of a planar levitated object using the acoustic jumping phenomenon

Nonlinear multi-frequency phonon lasers with active levitated optomechanics

Phonon lasers, which exploit coherent amplifications of phonons, are a means to explore nonlinear phononics, image nanomaterial structures and operate phononic devices. Recently, a phonon laser governed by dispersive optomechanical coupling has been demonstrated by levitating a nanosphere in an optical tweezer. Such levitated optomechanical devices, with minimal noise in high vacuum, can allow flexible control of large-mass objects without any internal discrete energy levels. However, it is challenging to achieve phonon lasing with levitated microscale objects because optical scattering losses are much larger than at the nanoscale. Here we report a nonlinear multi-frequency phonon laser with a micro-size sphere, which is governed by dissipative coupling. The active gain provided by a Yb3+-doped system plays a key role. It achieves three orders of magnitude for the amplitude of the fundamental-mode phonon lasing, compared with the passive device. In addition, nonlinear mechanical harmonics can emerge spontaneously above the lasing threshold. Furthermore, we observe coherent correlations of phonons for both the fundamental mode and its harmonics. Our work drives the field of levitated optomechanics into a regime where it becomes feasible to engineer collective motional properties of typical micro-size objects.

Acoustic Trap Step for Single-Axis Acoustic Levitators

Acoustic manipulation is extensively employed due to its versatility and noncontact capability. Although significant developments have been made in this field, the dynamic process of the acoustic trap position in the manipulation of acoustically levitated objects has not been fully investigated, hindering the development of acoustic manipulation technology. Herein, we propose the gravity-acoustic trap morphology ($G$-ATM) method to elucidate the dynamic process in single-axis levitators. First, the acoustic trap step is defined to describe the dynamic process. Then, based on the $G$-ATM method, the study is carried out for single-axis levitators from the radial and axial points of view. In the radial direction, the stage concept is proposed to explain the impact of gravity, the impact of acoustic trap morphology is expressed by radial acoustic radiation force distribution, and transitional levitation states are observed and explained. In the axial direction, the impact of gravity is analyzed from the kinetic energy perspective, the impact of acoustic trap morphology is presented by multiple adjacent acoustic traps, and the principle of proximity followed by the motion of levitated objects is proposed. Finally, all analysis results are verified by simulations and experiments. The work will help to improve the rapidity and stability of acoustic manipulation and promote the development of acoustic manipulation technology.

A reinforced CenterNet scheme on position detection of acoustic levitated objects

A reinforced CenterNet scheme on position detection of acoustic levitated objects

Natural oscillation frequencies of a Rayleigh sphere levitated in standing acoustic waves.

Acoustic levitation is an important method of container-free processing, which counteracts gravity through exerting the acoustic radiation force on levitated objects. The Gorkov potential function is used to simplify the calculation of the acoustic radiation force acting on a Rayleigh sphere whose radius is much smaller than the wave length. For the case of a plane standing wave levitation system, a systematic analysis of the sphere dynamics is provided in the axial direction, assuming a small perturbation around the stable equilibrium locations. A generalized extension to an arbitrary standing wave field is provided, which gives formal expressions of the axial and transverse natural oscillation frequencies for the sphere. Particular emphasis is put on the natural oscillation frequencies with and without taking gravity into consideration. The computational results for Gauss and Bessel standing waves are provided as two special cases, which show that the transverse natural oscillation frequency will be overestimated when neglecting gravity, especially for a sphere with a relatively large density. Corresponding experiments are conducted to verify the dependence of the transverse natural oscillation frequency on the sphere density. The results obtained in this work are expected to provide a theoretical guide for enhancing the levitation stability and inversing the physical parameters from the sphere dynamics.

Dipole moment background measurement and suppression for levitated charge sensors.

Optically levitated macroscopic objects are a powerful tool in the field of force sensing, owing to high sensitivity, absolute force calibration, environmental isolation, and the advanced degree of control over their dynamics that have been achieved. However, limitations arise from the spurious forces caused by electrical polarization effects that, even for nominally neutral objects, affect the force sensing because of the interaction of dipole moments with gradients of external electric fields. Here, we introduce a technique to measure, model, and eliminate dipole moment interactions, limiting the performance of sensors using levitated objects. This process leads to a noise-limited measurement with a sensitivity of 3.3 × 10−5 e. As a demonstration, this is applied to the search for unknown charges of a magnitude much below that of an electron or for exceedingly small unbalances between electron and proton charges.

Automatic traveling wave excitation of structures with imperfect cyclic symmetry

A method to generate traveling waves with maximal amplitudes in elastic structures with imperfect cyclic symmetric topology is presented. Traveling waves are useful in testing turbine-bladed disks and for the propulsion of ultrasonic motors. However, open-loop excitation of traveling waves may yield a partially standing wave due to imperfections and mode-mistuning. The present work puts forward a method that automatically locks onto the optimal excitation of the system, producing the largest possible pure propagating wave. The excitation uses autoresonance with modal filtering, and force projection control, utilizing optimum-seeking methodology. To validate the presented method, an experimental system consisting of a ring of coupled acoustic Helmholtz resonators was built. The ring was excited by the proposed method, and the ability to overcome the imperfections and automatically lock onto the optimal excitation was observed. In addition, the method was realized on a simulated, ultrasonic, acoustic levitation motor that utilizes traveling waves to control levitated objects.

An Approach to Networking a New Type of Artificial Orthogonal Glands within Orthogonal Endocrine Neural Networks

Currently, artificial intelligence and intelligent algorithms for the control of dynamic systems are the main focus for building Industry 4.0 services and developing novel, innovative industrial solutions. This paper proposes a novel intelligent control structure specifically tailored for treating environmental stimuli and disturbances in operational environments of dynamic systems. The structure is based on the Orthogonal Endocrine Neural Network (OENN) and Artificial Orthogonal Glands (AOGs). The operational mechanism of each AOG acquires and processes environmental stimuli and generates artificial hormone concentration values at the gland output. These values are introduced to the appropriate OENN layer to provoke the network with collected environmental insights. To verify the applicability of the proposed structure on a complex dynamical nonlinear system, it was tested in a laboratory environment on the laboratory magnetic levitation system (MLS). The main experimental goal was to test the tracking performance of a levitation object when the new control logic was applied. The results were compared with two additional intelligent algorithms and a default linear quadratic (LQ) control logic. OENN + AOG structure showed improved tracking performances compared with traditional LQ control and better adaptability to environmental conditions compared with similar existing solutions.

Acoustic levitation of multi-wavelength spherical bodies using transducer arrays of non-specialized geometries.

Recently, acoustic levitation of a wavelength-sized spherical object using a general-purpose ultrasonic transducer array was demonstrated. In this article, the possibility of extending the capabilities of such arrays to levitate multi-wavelength-sized objects is explored. The driving signals for the elements in the array are determined via numerical optimization of a physics-based cost function that includes components for trap stabilization. The cost function is balanced with an improved approach, mimicking dynamical de-weighting of the included components to avoid over-optimization of each individual component. Sound fields are designed and analyzed for levitation of objects with diameters up to 50 mm for various general-purpose simulated array configurations. For a 16 × 16 element transducer array, simulations predict levitation of spheres with diameters up to 20 mm (2.3 wavelengths), which is verified experimentally.

Mechanical Properties of Acoustically Levitated Granular Rafts

We investigate a model system for the rotational dynamics of inertial many-particle clustering, in which submillimeter objects are acoustically levitated in air. Driven by scattered sound, levitated grains self-assemble into a monolayer of particles, forming mesoscopic granular rafts with both an acoustic binding energy and a bending rigidity. Detuning the acoustic trap can give rise to stochastic forces and torques that impart angular momentum to levitated objects. As the angular momentum of a quasi-two-dimensional granular raft is increased, the raft deforms from a disk to an ellipse, eventually pinching off into multiple separate rafts, in a mechanism that resembles the breakup of a liquid drop. We extract the raft effective surface tension and elastic modulus and show that nonpairwise acoustic forces give rise to effective elastic moduli that scale with the raft size. We also show that the raft size controls the microstructural basis of plastic deformation, resulting in a transition from fracture to ductile failure.3 MoreReceived 17 June 2021Revised 14 February 2022Accepted 4 March 2022DOI:https://doi.org/10.1103/PhysRevX.12.021017Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAcoustic interactionsClusteringGranular materialsPolymers & Soft Matter

Measurement of Holding Force and Transportation Force Acting on Tabular Object in Near-Field Acoustic Levitation.

The holding force acting on a levitated object during near-field acoustic levitation has not been statically and directly measured so far. In this study, it was considered to realize such a measurement when a levitated object has a large displacement from the vibration source. In previous studies, under restricted conditions, the holding force has been calculated indirectly by image processing or measured from the balance with gravity by tilting the apparatus. In this article, the force was measured based on the magnetic force (MF) compensation principle. This is the first attempt to measure the force directly and statically under arbitrary conditions. One side of a rectangular rotor, which was placed above the acoustic radiation surface, received the holding force. The other side of the rotor received the MF generated by a solenoid. The holding force was estimated from the electric current flowing in the solenoid when the holding force and the MF were balanced. The holding force acting on the rotor surfaces was affected by the deviation between the rotor and the radiation surface. The holding force increased with increasing vibration amplitude or decreasing air gap between the rotor and the radiation surface. When the vibration sources were opposed, the holding force was affected by their vibration phase difference. The holding force was maximum at the opposite vibration phase and decreased with decreasing vibration phase difference. When the vibration sources were arranged in the transportation direction, the transportation force occurred and increased with increasing vibration amplitude of the destination vibration source. These measurement results agree well with the analysis results.

Searching for New Physics with a Levitated-Sensor-Based Gravitational-Wave Detector.

The levitated sensor detector (LSD) is a compact resonant gravitational-wave (GW) detector based on optically trapped dielectric particles that is under construction. The LSD sensitivity has more favorable frequency scaling at high frequencies compared to laser interferometer detectors such as LIGO and VIRGO. We propose a method to substantially improve the sensitivity by optically levitating a multilayered stack of dielectric discs. These stacks allow the use of a more massive levitated object while exhibiting minimal photon recoil heating due to light scattering. Over an order of magnitude of unexplored frequency space for GWs above 10kHz is accessible with an instrument 10 to 100meters in size. Particularly motivated sources in this frequency range are gravitationally bound states of the axion from quantum chromodynamics with decay constant near the grand unified theory scale that form through black hole superradiance and annihilate to GWs. The LSD is also sensitive to GWs from binary coalescence of sub-solar-mass primordial black holes and as-yet unexplored new physics in the high-frequency GW window.

Improvement of the non-contact conveyance performance to the vertical direction by using the electromagnet

Non-contact conveyance control system essentially should be ensured that the levitation object remains stable at a specific location below the electromagnet. In that case, it is important to keep the levitation object at a target position and suppress vibration caused by the conveyance motion. The lavitation control system is designed to equalize the closed-loop system to a second-order lag element to stabilize and ensure the appropriate response. However, the design criterion of the natural angular frequency of the closed-loop system, which is one of the design parameters, has not been clarified, therefore it was determined as an empirical value so far. In this study, investigations of the criterion of the design parameter were conducted through experiments. They show that the stability margin, which can be obtained by the self-identification experiment, can be applied directly to the design of the control feedback system. Consequently, it is expected that the performance of the non-contact conveyance improved for any kind of levitation object.

Design and Analysis of a Non-Contact Tension Testing Device Based on Magnetic Levitation

To facilitate mechanics testing in special environment, in this paper, a non-contact tension testing device was developed based on magnetic levitation technology. To find a floator that facilitates the alignment of tension force, electromagnetic analyses were performed using J-Mag software and a ring floator was found to be self-aligning. In addition, since the levitated objects need to bear a tension force, which will cause the nonlinearity of the magnetic levitation system to emerge, to address the nonlinear issue, a nonlinear mathematical model was established, and a centralized feedback linearization control algorithm was proposed. Furthermore, a tuning method for the control algorithm was proposed to deal with the mismatches between the controller and the plant. Moreover, a model for estimating specimen elongation was developed using support vector machine (SVM), the estimation results demonstrated that the range of the estimation error was between −0.1988mm and 0.2269mm, the root mean square error (RMSE) and coefficient of determination (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) were 0.0843mm and 98.76% respectively. Ultimately, a levitation experiment and a tension experiment were successfully performed, the levitation experiment results demonstrated that the proposed tuning method is effective and the centralized feedback linearization controller has stronger robustness to step disturbance than the traditional linear controller. The tension experiment results indicated that the whole control system copes well with an increasing tension force.

Levitating Objects Using Sound

Acoustic levitation uses sound waves to hold objects in mid-air. We are all familiar with the power of sound to make us dance and change our moods, but sound can also exert a physical force that is strong enough to levitate objects. To harness this force, we use loudspeakers to form a sound pattern so that the object is surrounded by very loud sound. Scientists have used these ideas to levitate small objects such as insects, as well as extremely small objects like individual cells. They can then manipulate these objects, much like a robot would, but without any moving parts. So far, only relatively small levitating forces have been generated but, in theory, much higher forces could be produced and levitation of objects even the size of humans might be possible. Despite this exciting possibility, you might not want to be acoustically levitated yourself, for good reason!