Acoustic Vortex Research Articles

Multitarget manipulation of off-axis acoustic vortices based on a focused sector-vortex transducer array

Multitarget manipulation of off-axis acoustic vortices based on a focused sector-vortex transducer array

Acoustic vortex-based dynamic lens for light focusing and steering.

This study explores a technique for light manipulation using an acoustic vortex generated by a high-intensity focused ultrasound transducer. The acoustic vortex forms a ring of bubble wall near the high-pressure region, creating a lens-like structure that can effectively focus a laser beam. The effects of varying acoustic pressures and dissolved oxygen content on the focused ultrasound and vortex waveforms were tested. Results showed that the vortex waveform could enhance the laser beam peak intensity by 55.6% and reduce its full width at half maximum from 1.16 mm to 0.91 mm. Additionally, the study demonstrated the capability to dynamically steer the laser beam at angles ranging from 0° to 0.7°, achieving precise control without the need for mechanical components. This technique offers a stable, real-time, and on-demand method for light manipulation, with potential applications in various liquid environments and heterogeneous media. The study also highlights current hardware limitations and suggests future improvements for optimizing parameters and further exploring related mechanisms.

Evaluation of inner product-based demultiplexing of vortex-based underwater acoustic communications signals in realistic environments.

Acoustic vortex beams have garnered recent interest as an avenue to improve underwater acoustic communication bandwidth and speed. Design and deployment of these systems in ocean environments and at operational ranges has yet to be demonstrated due to the challenging and dynamic nature of the underwater acoustic environment. This manuscript presents methods to model the time series of vortex-based communication signals in ocean environments using ray tracing algorithms. The methods are used to assess the effects of Doppler, ocean turbulence, positional error, and range-dependent environmental parameters on the inner product demultiplexing of the communication signals encoded in the acoustic orbital angular momentum.

Sound absorption of slit resonator with embedded aperture in linear and nonlinear regimes

This paper presents a slit resonator with embedded aperture (SREA) by embedding the slit-type neck into the cavity, and investigates its sound absorption characteristics in linear and nonlinear regimes. The theoretical acoustic impedance model of the SREA is established through transfer matrix method. The theoretical, simulation and experimental results demonstrate that the SREA enhances oscillating mass without altering acoustic capacity through the embedded slit-type neck, enabling it to achieve quasi-perfect absorption at lower frequencies with the same external geometry as traditional slit resonator. The formation and shielding of acoustic vortex caused by the high sound intensity increase the normalized acoustic resistance and decreases the acoustic reactance, causing the peak sound absorption coefficient to decline. This paper introduces a nonlinear correction expression for the normalized acoustic resistance of SREA by analogy with cylindrical neck.

Single-Beam Acoustic Tweezers for Cell Biology: Molecular to In Vivo Level.

Acoustic tweezers have attracted attention in various fields of cell biology, including in vitro single-cell and intercellular mechanics. Compared with other tweezing technologies such as optical and magnetic tweezers, acoustic tweezers possess stronger forces and are safer for use in biological systems. However, due to the limited spatial resolution or limited size of target objects, acoustic tweezers have primarily been used to manipulate cells in vitro. To extend the advantages of acoustic tweezers to other levels (e.g., molecular and in vivo levels), researchers have recently developed various types of acoustic tweezers such as single-beam acoustic tweezers (SBATs), surface acoustic wave (SAW) tweezers, and acoustic-streaming tweezers. Among these, SBATs utilize a single-focused beam, making the transducer and system simple, noninvasive, and capable of producing strong forces compared with other types of tweezers. Depending on the acoustic beam pattern, SBATs can be classified into Rayleigh regime, Mie regime, and acoustic vortex with different trapping dynamics and application levels. In this review, we provide an overview of the principles and configuration of each type of SBAT, their applications ranging from molecular to in vivo studies, and their limitations and prospects. Thus, this review demonstrates the significance and potential of SBAT technology in biophysics and biomedical engineering.

Описание физических эффектов акустического поля в волноводе мелкого моря

The field of the complex vector of acoustic intensity of a moving tonal low-frequency source in a regular waveguide of a shallow sea is investigated. The following phenomena are considered: phase front dislocations, singular points, an acoustic intensity vortex and the mechanism of its stability, angular momentum of the vortex, vortex rotor. The value of the signal-to-noise ratio has been established at which the appearance of a phase front dislocation and a vortex in the far field of the signal source is possible in a coherent field.

Characteristic analysis of the vortex excited using the photoacoustic transducer with a spiral light absorption surface

Abstract It is proved that the vortex acoustic field can be excited with laser by designing the photoacoustic transducer with a spiral light absorption surface. The generated acoustic field has a spiral phase wavefront, and the pressure on the central axis along its propagation direction is zero. The orbital angular momentum that can be used for positioning and manipulation of particles is formed by the vortex. The characteristics of the generated acoustic vortex at different frequency and detection position are analyzed for 1-5 topological charge. And the influence of the geometric configurations such as the width and size of logarithmic spiral slot are also studied for the achieving the desired vortex field with focused intensity.

Recognition of acoustic vortex fields based on a convolutional attention neural network

Recognition of acoustic vortex fields based on a convolutional attention neural network

Study Of Mixing Enhancement Of The 3-D Acoustofluidic Mixer Using Digital In-Line Holographic Micro Particle Tracking Velocimetry

In this study, the 3-D flow patterns and mixing performances are investigated for an acoustofluidic Y-junction micromixer using Digitial In-line Holographic Micro-Particle Tracking Velocimetry (DIHμPTV) and epi-fluorescence flow visualization. Two parallel longitudinal spines were placed in the channel to induce sustaining solenoidal 3-D acoustic streaming vortices, which work as the secondary flow in the mixing channel to reduce the diffusion mixing length and in turn enhance the mixing performances. The two spines have a triangular cross-section, with a base width of 0.2mm and a height of 0.3mm, placed 1.2mm apart from each other in a 2.8mm width and 1mm height channel. The Y-junction has two configurations, one has the spines directly connected to the side wall at the Y-junction, and the other microchannel has a gap between the two spines and a flat junction shape. The driving mechanism is provided by two piezoelectric disks, operating at 12 kHz oscillation frequency and 20V peak-to-peak amplitude. The 3-D flow patterns were recorded by the DIHμPTV in two measurement volumes to fully cover the test section’s height. The holographic reconstruction scheme is based on the 1st Rayleigh-Sommerfeld solution with an extra deconvolution step to improve the accuracy of the reconstruction of the depth position. The deconvolution step utilizes a simulated hologram of the Point-Spread Function (PSF) and reduces the depth uncertainty during the deconvolution of the raw data. The mixing performances of the acoustofluidic Y-junction micro-mixers were evaluated by the epi-fluorescence experiments, and the mixing indices were calculated and compared to verify the improvements compared to the Yjunction micromixers without the acoustic streaming vortices. The results confirmed the improvement of the mixing and the sustaining 3-D flow patterns even with a high flow rate, which could not be achieved with 2-D sharp-edge obstructions tested previously. The novel configuration may have the potential to inspire designs of high-throughput and low-pressure loss active micro-mixers.

Acoustic spin-controlled orbital rotations in double spiral acoustic beams

Similar to optical spin-orbit interactions (SOIs), acoustic SOIs are anticipated to offer fresh perspectives and capabilities for acoustic manipulation beyond conventional scalar degrees of freedom. However, the acoustic extrinsic SOIs caused by particular properties of the medium were seldom explored. Here, the acoustic extrinsic SOI is observed in a double spiral acoustic beam (DSAB), as evidenced by the rotation of the spatial intensity pattern along the propagation axis. The interaction of the acoustic plane wave with the well-designed artificial flat structure generates two non-paraxial focused acoustic vortices (NFAVs) with different spin angular momentums. The coaxial coupling between them leads to acoustic spin-controlled orbital rotation (SOR). Theoretical formulations, supported by numerical simulations and experimental results, are provided to demonstrate the validity of acoustic SOR. Our work provides new perspectives and capabilities for understanding sound processing, and may open an avenue for the development of spin-orbit acoustics.

Airborne Acoustic Vortex End Effector-based Contactless, Multi-mode, Programmable Control of Object Surfing.

Tweezers based on optical, electric, magnetic, and acoustic fields have shown great potential for contactless object manipulation. However, current tweezers designed for manipulating millimeter-sized objects such as droplets, particles, and small animals, exhibit limitations in translation resolution, range, and path complexity. Here, we introduce a novel acoustic vortex tweezers system, which leverages a unique airborne acoustic vortex end effector integrated with a three degree-of-freedom (DoF) linear motion stage, for enabling contactless, multi-mode, programmable manipulation of millimeter-sized objects. The acoustic vortex end effector utilizes a cascaded circular acoustic array, which is portable and battery-powered, to generate an acoustic vortex with a ring-shaped energy pattern. The vortex applies acoustic radiation forces to trap and spin an object at its center, simultaneously protecting this object by repelling other materials away with its high-energy ring. Moreover, our vortex tweezers system facilitates contactless, multi-mode, programmable object surfing, as demonstrated in experiments involving trapping, repelling, and spinning particles, translating particles along complex paths, guiding particles around barriers, translating and rotating droplets containing zebrafish larvae, and merging droplets. With these capabilities, we anticipate that our tweezers system will become a valuable tool for the automated, contactless handling of droplets, particles, and bio-samples in biomedical and biochemical research.

Tunable acoustic vortex generation by a compact rotating disk

Acoustic vortices (AVs) carry orbital angular momentum (OAM), showing great promise in advancing communication, biomedicine, and metrology. An ideal OAM generation method that realizes the tunability of AV topological charge and working frequency in a compact way is strongly desired. Here, we utilize aerodynamic dipole sources from a rotating disk to generate AV. This method generates AVs with different topological charges through the interference of these dipole sources at the angular rotation frequency and its multiples. These AVs exhibit high purity, and their three-dimensional characteristics are explored. Furthermore, our experiment demonstrates that the generated AVs significantly enhance the sound field amplitude at their working frequency, which is the product of the topological charge and angular frequency. The results also verify that this amplitude enhancement effect is positively correlated with the AV’s stability and achieves the contactless detection of disk rotation information. The demonstrated method provides expanded versatility for OAM-based applications.

Robot-assisted chirality-tunable acoustic vortex tweezers for contactless, multifunctional, 4-DOF object manipulation.

Robotic manipulation of small objects has shown great potential for engineering, biology, and chemistry research. However, existing robotic platforms have difficulty in achieving contactless, high-resolution, 4-degrees-of-freedom (4-DOF) manipulation of small objects, and noninvasive maneuvering of objects in regions shielded by tissue and bone barriers. Here, we present chirality-tunable acoustic vortex tweezers that can tune acoustic vortex chirality, transmit through biological barriers, trap single micro- to millimeter-sized objects, and control object rotation. Assisted by programmable robots, our acoustic systems further enable contactless, high-resolution translation of single objects. Our systems were demonstrated by tuning acoustic vortex chirality, controlling object rotation, and translating objects along arbitrary-shaped paths. Moreover, we used our systems to trap single objects in regions with tissue and skull barriers and translate an object inside a Y-shaped channel of a thick biomimetic phantom. In addition, we showed the function of ultrasound imaging-assisted acoustic manipulation by monitoring acoustic object manipulation via live ultrasound imaging.

Numerical investigation of acoustic streaming vortices in cylindrical tube arrays

Abstract Acoustic streaming has a significant effect on accelerating material mixing and flow field disturbance. To explore the characteristics of acoustic streaming in the cylindrical tube array field under the action of an acoustic wave, we derive the dimensionless acoustic streaming control equation and establish a numerical calculation model of acoustic streaming. The effects of acoustic incidence angle, acoustic Reynolds number, and Strouhal number on the acoustic streaming vortex flow field in the tube array were investigated. The numerical results show that with the change in acoustic parameters, the acoustic streaming in the tube array presents rich changes in the vortex flow field, and there are flow field phenomena such as shrinking, merging, tearing, and splitting of the vortex structure. Toward the walls of each tube, there is a strong acoustic streaming flow velocity. Besides, there is also a large streaming velocity on the interface of the adjacent acoustic streaming vortices. The inner streaming vortex structure in the acoustic boundary layer decreases with the increase in the acoustic Reynolds number, but the intensity of the inner streaming vortex and outer streaming vortex increases rapidly, and the disturbance effect of the flow field is enhanced. With the increase in the dimensionless acoustic frequency (or Strouhal number), although the structure and intensity of the inner streaming vortex decrease, the velocity gradient on the wall of the cylindrical tube increases, which is beneficial to destroy the flow boundary layer of the cylindrical tube wall and accelerate the instability of the wall flow field.

Enhanced Broadband Manipulation of Acoustic Vortex Beams Using 3‐bit Coding Metasurfaces through Topological Optimization (Small 19/2024)

Enhanced Broadband Manipulation of Acoustic Vortex Beams Using 3‐bit Coding Metasurfaces through Topological Optimization (Small 19/2024)

Optimization method to construct multiple acoustic vortices for holograms

In this study, the novel optimization method of holograms based on spin density is developed by introducing a new degree of freedom—spin angular momentum density into the direct search method. This approach leverages the programmability of numerous pixels in holograms and eliminates the need for meticulous management of amplitude and phase at discrete points, facilitating the construction of multiple first-order acoustic vortices. We efficiently construct a pattern of 40 vortices within a plane and vortices with different intensities and structures using this approach. We also illustrate the practical application of our design methodology by showcasing its ability to manipulate particles through the transfer of angular momentum from vortices to particles. This work not only advances our understanding of acoustic vortices but also explore a new degree of freedom in designing holograms, potentially enhancing the capacity of holograms.

Effect of Intake Acoustic Reflection on Blade Vibration Characteristics

Recent studies in turbomachinery have shown that the phase of acoustic wave reflection within an intake can have either positive or negative effects on the aeroelastic stability of fan rotor blades. However, the typical flow structures, such as the shock wave, within rotor blade passages with acoustic wave reflection remain unclear. The aim of this research was to address this gap by investigating how these flow structures impact blade aeroelastic stabilities with acoustic wave reflections. The focus of this study was the NASA Rotor 67 blade with an extended intake. Moreover, a bump is incorporated on the shroud at different distances from the fan to reflect acoustic waves of varying phases. Utilizing the energy method, variations in the aerodynamic work density on blade surfaces were calculated under different phases of reflected acoustic waves. Analysis indicates that the spatial position of the shock wave undergoes periodic changes synchronized with the phase of acoustic reflection, marking the first instance of such an observation. This synchronization is identified as the primary factor causing variations in the aeroelastic stability of blades due to acoustic wave reflection, contributing to a deeper understanding of the mechanism behind acoustic flutter. The acoustic–vortex coupling at the blade tip leads to unpredictable variations in unsteady pressures on the blade suction surface, although its effect on blade aeroelastic stabilities is relatively limited compared to that of the shock wave.

Broadband asymmetric acoustic vortex generator based on integrative meta-atoms

The significance of asymmetric acoustic vortices primarily derives from their distinctive influence on acoustic vortex applications, such as acoustic communication receiving and sending isolation. However, the existing asymmetric acoustic vortices suffer from strong narrow-band confinement. In this paper, we eliminate this constraint by proposing a novel asymmetric scheme based on integrative meta-atoms (IMs). The IM is assembled by a phase gradient metasurface (PGM) and a mode selection structure (MSS), which serve the mode conversion and selection functions respectively. The PGM is constructed by a coiling-up space, converting the incident plane wave mode into a first-order vortex mode. We introduce three mirror scatterers in a cylindrical waveguide to form the MSS, allowing the first-order vortex mode to pass but blocking the plane wave mode in the mode band gap. The mode selection mechanism of MSS is revealed by employing the dispersion relation of the unit cell and the mode transmission performance of the MSS. By coupling the acoustic modulation effects of PGM and MSS, the asymmetric generation for the first-order vortex mode is realized, and further demonstrated numerically and experimentally. Significantly, the designed IMs exhibit commendable performance in both broadband and mode purity. In detail, a relative bandwidth of 25.3 % and a purity metric of 0.88 can be achieved. Our study may offer an alternative approach to producing asymmetric acoustic vortex devices, paving the way for a myriad of advanced applications.

Selective Sparse Sampling of Water Droplets in Oil with Acoustic Tweezers.

In microfluidics, water droplets are often used as independent biochemical microreactor units, enabling the implementation of massively parallel screening assays where only a few of the reacting water droplets yield a positive result. However, sampling the product of these few successful reactions is an unsolved challenge. One possible solution is to use acoustic tweezers, which are lab-free, easily miniaturized, and biocompatible manipulation tools, and existing acoustic tweezers manipulating particles or cells, and water droplet manipulation in oil with an acoustic tweezer is absent. The first challenge in attempting to recover a few water droplets from a large batch is the selective manipulation of water droplets in an oil system. In this paper, we trap and manipulate single water droplets in oil using integrated single-beam (focused beam/vortex beam) acoustic tweezers for the first time. We find that water droplets with a diameter smaller than half a wavelength are trapped by acoustic vortices, while larger ones are better captured by focused acoustic beams. It is the first step to extract the target water droplet microreactors (positive ones) in an oil system and analyze their content. Compared to previous techniques, such as fluorescence-activated cell sorting (FACS), our technique is sparse, meaning that the sampling time is proportional to the number of droplets required and very insensitive to the total number of microreactors, making it well suited for large-scale screening assays.

Acoustic polygonal Bessel vortices based on metasurfaces

Acoustic polygonal Bessel vortices based on metasurfaces