Acoustic Manipulation Research Articles

Topological pumping in acoustic waveguide arrays with hopping modulation

Thouless pumping is the adiabatic transportation of quantized charge, which is regarded as the dynamic version of the quantum Hall effect. Here we propose the design of an acoustic system to demonstrate the topological pumping characterized by transporting acoustic energy from one side to the opposite. The system is composed of coupled acoustic waveguide arrays with modulated coupling along both cross-sections and the propagating direction. We explore multiple topological phases by introducing rich spatial frequency or enlarged range of the hopping modulation. Such distinct topological phases are evidenced by adiabatic evolution of the edge states, where the acoustic system varies continuously and slowly along the state propagating direction. The robustness behavior of the edge states transport is also verified with numerical simulations to imply their topology origin. Our work provides a route to realize topological phases and utilize the corresponding edge states in waveguide arrays that can lead to versatile acoustic wave manipulation applications.

Outer Acoustic Streaming Flow Driven by Asymmetric Acoustic Resonances.

While boundary-driven acoustic streaming resulting from the interaction of sound, fluids and walls in symmetric acoustic resonances have been intensively studied in the literature, the acoustic streaming fields driven by asymmetric acoustic resonances remain largely unexplored. Here, we present a theoretical and numerical analysis of outer acoustic streaming flows generated over a fluid–solid interface above which a symmetric or asymmetric acoustic standing wave is established. The asymmetric standing wave is defined by a shift of acoustic pressure in its magnitude, i.e., , and the resulting outer acoustic streaming is analyzed using the limiting velocity method. We show that, in symmetric acoustic resonances (), on a slip-velocity boundary, the limiting velocities always drive fluids from the acoustic pressure node towards adjacent antinodes. In confined geometry where a slip-velocity condition is applied to two parallel walls, the characteristics of the obtained outer acoustic streaming replicates that of Rayleigh streaming. In an asymmetric standing wave where , however, it is found that the resulting limiting velocity node (i.e., the dividing point of limiting velocities) on the slip-velocity boundary locates at a different position to acoustic pressure node and, more importantly, is shown to be independent of , enabling spatial separation of acoustic radiation force and acoustic streaming flows. The results show the richness of boundary-driven acoustic streaming pattern variations that arise in standing wave fields and have potentials in many microfluidics applications such as acoustic streaming flow control and particle manipulation.

Non-resonant waveguiding-spiralizer for generating acoustic orbital angular momentum with arbitrary number of channels

Acoustic orbital angular momentum (a-OAM) has important application values in several fields such as high-capacity acoustic communication or manipulation of objects. In this paper, a non-resonant waveguiding-spiralizer based on the spiral structure was proposed for generating a-OAM and achieved the wavefront rotation with any channels. Compared with active a-OAM generating devices, these waveguiding-spiral structures were compact enough that could be easily fabricated through three-dimensional (3D) printing technology. While compared with other passive a-OAM generating devices, the principle of wavefront rotation realized by the proposed device was geometrical aisles guiding, which belongs to the non-resonant structure. Therefore, it could effectively reduce the energy loss of sound wave, and avoid the narrow-band feature caused by the resonant structure. Most importantly, the working frequency could be adjusted to any working frequency bands by geometric scaling, and it could work in a variety of media or harsh conditions. In addition, the waveguiding-spiralizer could be designed for any number of channels to realize the multiplexing communication.

Study on Particle Manipulation in a Metal Internal Channel under Acoustic Levitation.

In order to study the acoustic levitation and manipulation of micro-particles in the heterogeneous structures inside metal, a test system for internal levitation in three-dimensional space is designed, establishing the 3D motion model of ultrasonic levitation and manipulation of micro-particles. The relationship between levitation force, particle diameter, internal channel size, and transmission thickness is established through the motion manipulation tests of multi-configuration channel levitation micro-particles in components. The results show that the proposed method can realize the following movement of levitation micro-particles at a higher speed and the control of motion accuracy in three-dimensional space. The micro-particles can be reliably suspended and continuously moved inside the components along a predesigned motion trajectory. The results provide an effective and feasible processing scheme for direct processing through the internal spatial structure.

Acoustic manipulation of fractal metamaterials with negative properties and near-zero densities

Acoustic metamaterials have high potential in diverse applications, including acoustic cloaking, sound tunneling, wavefront reshaping, and sound insulation. In the present study, new metamaterials consisting of spatially coiled units are designed and fabricated to manipulate sound waves in the range of 0–1600 Hz. The effective acoustic properties and band diagrams of the metamaterials are studied. The simulation and experimental results demonstrate that the metamaterials provide an effective and feasible approach for designing acoustic devices such as sound cloaking and insulators.

Listening in the Mix: Lead Vocals Robustly Attract Auditory Attention in Popular Music

Listeners can attend to and track instruments or singing voices in complex musical mixtures, even though the acoustical energy of sounds from individual instruments may overlap in time and frequency. In popular music, lead vocals are often accompanied by sound mixtures from a variety of instruments, such as drums, bass, keyboards, and guitars. However, little is known about how the perceptual organization of such musical scenes is affected by selective attention, and which acoustic features play the most important role. To investigate these questions, we explored the role of auditory attention in a realistic musical scenario. We conducted three online experiments in which participants detected single cued instruments or voices in multi-track musical mixtures. Stimuli consisted of 2-s multi-track excerpts of popular music. In one condition, the target cue preceded the mixture, allowing listeners to selectively attend to the target. In another condition, the target was presented after the mixture, requiring a more “global” mode of listening. Performance differences between these two conditions were interpreted as effects of selective attention. In Experiment 1, results showed that detection performance was generally dependent on the target’s instrument category, but listeners were more accurate when the target was presented prior to the mixture rather than the opposite. Lead vocals appeared to be nearly unaffected by this change in presentation order and achieved the highest accuracy compared with the other instruments, which suggested a particular salience of vocal signals in musical mixtures. In Experiment 2, filtering was used to avoid potential spectral masking of target sounds. Although detection accuracy increased for all instruments, a similar pattern of results was observed regarding the instrument-specific differences between presentation orders. In Experiment 3, adjusting the sound level differences between the targets reduced the effect of presentation order, but did not affect the differences between instruments. While both acoustic manipulations facilitated the detection of targets, vocal signals remained particularly salient, which suggest that the manipulated features did not contribute to vocal salience. These findings demonstrate that lead vocals serve as robust attractor points of auditory attention regardless of the manipulation of low-level acoustical cues.

Janus acoustic metascreen with nonreciprocal and reconfigurable phase modulations

Integrating different reliable functionalities in metastructures and metasurfaces has become of remarkable importance to create innovative multifunctional compact acoustic, optic or mechanical metadevices. In particular, implementing different wave manipulations in one unique material platform opens an appealing route for developing integrated metamaterials. Here, the concept of Janus acoustic metascreen is proposed and demonstrated, producing two-faced and independent wavefront manipulations for two opposite incidences. The feature of two-faced sound modulations requires nonreciprocal phase modulating elements. An acoustic resonant unit cell with rotating inner core, which produces a bias by a circulating fluid, is designed to achieve high nonreciprocity, leading to decoupled phase modulations for both forward and backward directions. In addition, the designed unit cell consisting of tunable phase modulators is reconfigurable. A series of Janus acoustic metascreens including optional combinations of extraordinary refraction, acoustic focusing, sound absorption, acoustic diffusion, and beam splitting are demonstrated through numerical simulations and experiments, showing their great potential for acoustic wavefront manipulation.

Design and manufacturing of monolithic mechanical metastructures governing ultrawide low frequency three-dimensional bandgaps

The design and manufacturing of innovative monolithic mechanical metastructures capable of inducing ultrawide low-frequency subwavelength bandgaps, incorporating simple structure morphology and reliable performance, have received enormous attention amongst the scientific community due to the marvellous dynamic characteristics and their potential industrial application in vibration and noise control technology. Specifically, more emphasis is devoted to the mechanical and dynamical properties and innovative design of phononic structures, which leads to periodic systems with unprecedented mechanical and effective medium properties, including ultrawide bandgaps. The present study proposes two types of easily manufacturable 3-D monolithic mechanical metastructure designs, which possess the ability to induce ultrawide low frequency three-dimensional (3-D) complete bandgaps. Employing the principle of mode separation and numerical modal analysis through two different FEM codes, the generation mechanism of ultrawide bandgaps is examined and discussed. The finite supercell structure for both designs is created and numerical frequency response study is performed to validate the claimed properties. The 3-D prototypes are prepared by additive manufacturing technology and vibration tests are performed to confirm the wave attenuation over a broadband frequency range. Both numerical and experimental results are compared and possible discrepancies are discussed. The proposed monolithic metastructures can undoubtedly be manufactured by the conventional additive manufacturing technology, with potential applications in metadevices, where low frequency ultrawide multi-directional vibrations and noise control is desirable. Furthermore, the proposed designs can be employed for underwater acoustic wave manipulation and design of metasurfaces to be embedded at the water surface for ultrahigh transmission of acoustic waves at the water-air interface. • Additively manufactured metastructure designs, governing low-frequency ultrawide 3-D bandgaps, are studied. • Based on the principle of mode separation, the bandgap generation mechanism is examined and discussed. • Two finite element analysis codes are utilised for the numerical study to investigate the performance of ultrawide bandgaps. • Vibration test is performed on 3-D printed prototypes, which validates the efficacy of vibration attenuation. • Proposed metastructures can be deployed for elastic and acoustic waves manipulation over an ultrawide frequency range.

Even violins can cry: specifically vocal emotional behaviours also drive the perception of emotions in non-vocal music.

A wealth of theoretical and empirical arguments have suggested that music triggers emotional responses by resembling the inflections of expressive vocalizations, but have done so using low-level acoustic parameters (pitch, loudness, speed) that, in fact, may not be processed by the listener in reference to human voice. Here, we take the opportunity of the recent availability of computational models that allow the simulation of three specifically vocal emotional behaviours: smiling, vocal tremor and vocal roughness. When applied to musical material, we find that these three acoustic manipulations trigger emotional perceptions that are remarkably similar to those observed on speech and scream sounds, and identical across musician and non-musician listeners. Strikingly, this not only applied to singing voice with and without musical background, but also to purely instrumental material.This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

Acoustically induced coherent spin trapping.

Spin centers are promising qubits for quantum technologies. Here, we show that the acoustic manipulation of spin qubits in their electronic excited state provides an approach for coherent spin control inaccessible so far. We demonstrate a giant interaction between the strain field of a surface acoustic wave (SAW) and the excited-state spin of silicon vacancies in silicon carbide, which is about two orders of magnitude stronger than in the ground state. The simultaneous spin driving in the ground and excited states with the same SAW leads to the trapping of the spin along a direction given by the frequency detuning from the corresponding spin resonances. The coherence of the spin-trapped states becomes only limited by relaxation processes intrinsic to the ground state. The coherent acoustic manipulation of spins in the ground and excited state provides new opportunities for efficient on-chip quantum information protocols and coherent sensing.

Poroelastic microlattices for underwater wave focusing

Metamaterials with microscale architectures, e.g., microlattices, can exhibit extreme quasi-static mechanical response and tailorable acoustic properties. When coupled with pressure waves in surrounding fluid, the dynamic behavior of microlattices in the long wavelength limit can be explained in the context of Biot’s theory of poroelasticity. In this work, we exploit the elastoacoustic wave propagation within 3D-printed polymeric microlattices to incorporate a gradient of refractive index for underwater ultrasonic lensing. Experimentally and numerically derived dispersion curves allow the characterization of acoustic properties of a fluid-saturated elastic lattice. A modified Luneburg lens index profile adapted for underwater wave focusing is demonstrated via the finite element method and immersion testing, showcasing a computationally efficient poroelasticity-based design approach that enables accelerated design of acoustic wave manipulation devices. Our approach can be applied to the design of acoustic metamaterials for biomedical applications featuring focused ultrasound.

Acoustic radiation force on a rigid cylinder near rigid corner boundaries exerted by a Gaussian beam field

Acoustic manipulation is one of the well-known technologies of particle control and a top research in acoustic field. Calculation of acoustic radiation force on a particle nearby boundaries is one of the critical tasks, as it approximates realistic applications. Nevertheless, it is quite difficult to solve the problem by theoretical method when the boundary conditions are intricate. In this study, we present a finite element method numerical model for the acoustic radiation force exerting on a rigid cylindrical particle immersed in fluid near a rigid corner. The effects of the boundaries on acoustic radiation force of a rigid cylinder are analyzed with particular emphasis on the non-dimensional frequency and the distance from the center of cylinder to each boundary. The results reveal that these parameters play important roles in acoustic manipulation for particle-nearby complicated rigid boundaries. This study verifies the feasibility of numerical analysis on the issue of acoustic radiation force calculation close to complex boundaries, which may provide a new idea on analyzing the acoustic particle manipulation in confined space.

Large-aperture 256-element fully populated random array for therapeutic ultrasound applications: Experimental study of its functionality and characterization of the radiated field

Recently, a new method has been proposed for designing random high-intensity focused ultrasound (HIFU) arrays with the maximum possible filling factor and polygonal elements of equal area, based on capacity constrained tessellation [Rosnitskiy et al., IEEE Trans. UFFC (2018)]. Following this approach, a 256-element piezocomposite array with a radius of curvature of 150 mm, a diameter of 200 mm, and an operating frequency of 1.2 MHz was designed at the Laboratory for Industrial and Medical Ultrasound (LIMU) of Moscow State University. The array was subsequently manufactured by Imasonic (France). It can be driven using a Verasonics ultrasound engine. Electrical matching was performed for each element using matching network created by Image Guided Therapy (France). This report presents the system design procedure and experimental results for array characterization using acoustic holography and acoustic power measurements using the radiation force balance. In addition, a theoretical study was carried out using the “HIFU beam” simulator developed at LIMU (freely available at www.limu.msu.ru) to assess the array's ability to achieve highly nonlinear regimes with shocked pressure waveforms. The possibility of using the array for HIFU applications such as acoustic levitation and manipulation, histotripsy and transcostal HIFU therapy is discussed. [Work supported by RSF 19-12-00148.]

Acoustic manipulation of objects in vivo

Acoustic radiation forces can trap and manipulate objects in three-dimensional space (3D). The state of the art in acoustic trapping has demonstrated the ability to move small or lightweight objects using single or multiple transducers. For certain medical applications, acoustic manipulation can be utilized to control foreign objects in the body, such as kidney stones. However, difficulties from these applications include the ability to control large solid objects, transmitting robust acoustic beams through the skin, and the use of a single source due to limited acoustic window in the body. The goal of this work was to use a 1.5 MHz, focused, multi-element array to synthesize specific acoustic beams to trap, levitate, and steer kidney stone models (glass spheres) in a water bath and urinary bladders of live pigs. Stable acoustic traps were investigated numerically and experimentally in water bath to design a protocol for the 3D manipulation strategies used invivo . Three programmed path were used to levitate and manipulate glass spheres in live pigs. The motion was recorded using a camera and a synchronized ultrasound imaging probe. Deviation from the intended paths was on average <10%. [Work supported by NIH P01-DK043881, K01-DK104854, R01EB7643, and RFBR 20-02-00139.]

Positioning, transfer, and rotation movements of particles manipulated by a novel piezoelectric acoustofluidic device with multiple vibration modes

Acoustic-based manipulation platforms are the preferred device to manipulate particles in analytical chemistry and biomedicine due to their label-free and high biocompatibility. As a significant wave mode of the acoustic manipulation method, bulk acoustic waves (BAWs) have been wildly concerned by academia and industry. To realize the high-precise multi-mode manipulation of particles with a simple structure, a BAWs-based piezoelectric acoustofluidic device is proposed. It is composed of a Langevin transducer and a disk with a circular groove. Two vibration modes of the disk with three and five node circles, respectively, are used to manipulate particles to position, transfer, and rotate. A non-nodal acoustic trap is induced in the disk center by producing its first out-of-plane bending vibration mode. In this acoustic trap, the spherical particles and irregularly shaped particles can be fixed entirely and rotated, respectively. Simultaneously, the disk center is an antinode of the acoustic field induced by the second disk out-of-plane bending vibration mode, leading to that the trapped particles can be equidistantly transferred from the disk center to the nearest node. The effectiveness of the proposed device is verified by simulations and experiments. With appropriate control parameters, the minimum position fluctuation of the submillimeter-hollow-glass sphere (SHGS) after being positioned is 0.32% of its diameter. Moreover, the maximum transfer speed of the SHGS and maximum rotation speed of the cylindrical metal wire are 130.8 mm s−1 and 23.51 rad s−1, respectively. This proposed device is capable of multiple manipulation modes for particles with simple control strategy, providing a novel method for designing a BAWs-based device to achieve the manipulation of particles.

Contextually-relevant enhancement of non-native phonetic contrasts

One important factor that contributes to successful speech communication is an individual’s ability to speak more clearly when their listeners have difficulty understanding their speech. Though previous studies have demonstrated that native talkers implement acoustic–phonetic speech enhancements to ensure that their speech is understood by listeners, how non-native talkers employ goal-oriented enhancements is less well-understood. Here, we examine acoustic characteristics of speech enhancements produced by native and non-native English talkers of varying proficiency. Specifically, we investigate native Mandarin learners of English. The results show that non-native talkers’ ability to enhance a specific sound contrast differed depending on their familiarity with the target English contrast from their native language experience (Mandarin), as well as their English proficiency level. These results highlight that talkers are able to enhance their speech in native and non-native languages, but also suggest that this flexibility is shaped by the talkers’ target language proficiency and the type of acoustic manipulation involved in the adaptation.

Acoustic manipulation on microbubbles along arbitrary trajectories and adjustable destination

Non-diffracting Bessel acoustic beam that propagates in three dimensions has the properties of self-healing, self-bending, and self-acceleration, giving them many potential applications. Here, we report a zero-order Bessel-like acoustic beam that propagates along a curved trajectory with a phase-modulating acoustic holographic lens. Its pressure distribution on the transverse section approximately conforms to the zero-order Bessel function, and the self-healing property is found. In addition, the maximum point of acoustic intensity on the beam mainlobe can be adjusted by the change in the acoustic frequency. Microbubbles can be forced toward the maximum point along the predefined curve. Therefore, such a beam can be used for the directional transportation of microbubbles with a predefined curve and an adjustable destination. We have numerically calculated the primary Bjerknes force, including the oscillation of the microbubbles with the shell and experimentally proved the curved trajectory and the adjustable destination of the transportation of microbubbles. The proposed method uses the conservative part of the radiation force, which controls the trajectory of microbubbles by the amplitude gradient. The relatively free design of the transport trajectory and destination makes the approach suitable in vivo.

A novel U-shaped acoustic-manipulated design to enhance the performance of low-efficiency filters for sub-micron particles

Acoustic manipulation is a non-contact process that applies acoustic waves to immobilize particles into a specific region for a variety of potential applications. This provides an alternative way to address air ventilation requirements where building systems are becoming smarter and more efficient. Development of such a process within confined spaces can incorporate microscopic interactions to filter aerosol-based particulate matter (PM). In real-engineering conditions, it is hard to filter sub-micron particles (0.25–1.0 μm) than super-micron particles (> 2.5 μm) by using low-grade filters. The objectives of this work are twofold. First, we propose a new acoustic-driven pre-filtering device (i.e., a U-shaped resonant acoustic chamber) that can improve the working efficiency of low-grade filters for capturing such particles. Second, the device can optimize spatial homogeneity to enhance the removal efficiency of airborne particles under lower sound intensity requirements. The U-shaped acoustic-driven device in the form of a resonant chamber allows PM to reside at the pressure node of a standing wave. Experimental studies are conducted to verify the present design. The results show that an overall filtration efficiency of up to 89% for 1.0-μm airborne particles can be achieved when the acoustic-driven device is coupled together with a low-grade MERV-6 coarse filter. As a standalone device, the acoustic effect works well for the sub-micron particles with a filtration efficiency of up to 61% under a lower sound pressure level (116 dB) than as previously reported in the literature. In the analysis, we also discuss the performance dependence on frequency, sound pressure level and flow rate in terms of particle size distribution. The relevance of this research is a major step towards engineering an acoustic-based pre-filtering technique for developing future innovative ventilation solutions.

Embedded Microbubbles for Acoustic Manipulation of Single Cells and Microfluidic Applications.

Acoustically excited microstructures have demonstrated significant potential for small-scale biomedical applications by overcoming major microfluidic limitations. Recently, the application of oscillating microbubbles has demonstrated their superiority over acoustically excited solid structures due to their enhanced acoustic streaming at low input power. However, their limited temporal stability hinders their direct applicability for industrial or clinical purposes. Here, we introduce the embedded microbubble, a novel acoustofluidic design based on the combination of solid structures (poly(dimethylsiloxane)) and microbubbles (air-filled cavity) to combine the benefits of both approaches while minimizing their drawbacks. We investigate the influence of various design parameters and geometrical features through numerical simulations and experimentally evaluate their manipulation capabilities. Finally, we demonstrate the capabilities of our design for microfluidic applications by investigating its mixing performance as well as through the controlled rotational manipulation of individual HeLa cells.

Acoustic Vortices via Nonlocal Metagratings

Vortex beams carrying orbital angular momentum enrich the wave-matter interaction physics and show great potential applications, such as optical or acoustic tweezers and long-range signal communication. However, passive vortex generators commonly suffer from drawbacks of low efficiency and bulky configurations. In this work, by harnessing nonlocal coupling between subunits, we present a thin layer of metagratings to change efficiently the topological charge of a vortex beam in a waveguide. Our numerical and experimental results show that thin and planar metagratings can convert a plane-wave mode into first-, second-, and third-order vortex beams with nearly perfect efficiency (more than 99%). Our work breaks through the barrier to obtain highly efficient acoustic vortex beams and may offer opportunities for the development of devices for acoustic communication and manipulation.