Showing papers by "Zhengyou Liu published in 2016"
TL;DR: The acoustic version of valley states in sonic crystals are studied and a vortex nature of such states is revealed and the valley selection enables a handy way to create vortex matter in acoustics, in which the vortex chirality can be controlled flexibly.
Abstract: Valleytronics is quickly emerging as an exciting field in fundamental and applied research. In this Letter, we study the acoustic version of valley states in sonic crystals and reveal a vortex nature of such states. In addition to the selection rules established for exciting valley polarized states, a mimicked valley Hall effect of sound is proposed further. The extraordinary chirality of valley vortex states, detectable in experiments, may open a new possibility in sound manipulations. This is appealing to scalar acoustics that lacks a spin degree of freedom inherently. In addition, the valley selection enables a handy way to create vortex matter in acoustics, in which the vortex chirality can be controlled flexibly. Potential applications can be anticipated with the exotic interaction of acoustic vortices with matter, such as to trigger the rotation of the trapped microparticles without contact.
327 citations
TL;DR: Based on the Huygens-Fresnel principle, a metasurface structure is designed to generate a sound vortex beam in an airborne environment as discussed by the authors, which is constructed by a thin planar plate perforated with a circular array of deep subwavelength resonators with desired phase and amplitude responses.
Abstract: Based on the Huygens-Fresnel principle, a metasurface structure is designed to generate a sound vortex beam in airborne environment. The metasurface is constructed by a thin planar plate perforated with a circular array of deep subwavelength resonators with desired phase and amplitude responses. The metasurface approach in making sound vortices is validated well by full-wave simulations and experimental measurements. Potential applications of such artificial spiral beams can be anticipated, as exemplified experimentally by the torque effect exerting on an absorbing disk.
95 citations
TL;DR: In this article, an acoustic vortex beam was generated by a single source incident upon a structured brass plate with Archimedean spiral grating engraved on the back surface, which was then used to demonstrate acoustic angular momentum transfer to an acoustic absorptive matter.
Abstract: In this work, we give direct demonstration of acoustic radiation force and acoustic torque on particles exerted by an acoustic vortex beam, which is realized by an acoustic artificial structure plate instead of traditional transducer arrays. First, the first order acoustic vortex beam, which has the distinctive features of a linear and continuous phase variation from −π to π around its propagation axis and a magnitude null at its core, is obtained through one single acoustic source incident upon a structured brass plate with Archimedean spiral grating engraved on the back surface. Second, annular self-patterning of polystyrene particles with a radius of 90 μm is realized in the gradient field of this acoustic vortex beam. In addition, we further exhibit acoustic angular momentum transfer to an acoustic absorptive matter, which is verified by a millimeter-sized polylactic acid disk self-rotating in water in the acoustic field of the generated vortex beam.
85 citations
01 Aug 2016
TL;DR: In this article, the acoustic version of valley states in sonic crystals and reveal a vortex nature of such states are studied. But the selection rules established for exciting valley polarized states, a mimicked valley Hall effect of sound is proposed further.
Abstract: Valleytronics is quickly emerging as an exciting field in fundamental and applied research. In this Letter, we study the acoustic version of valley states in sonic crystals and reveal a vortex nature of such states. Besides the selection rules established for exciting valley polarized states, a mimicked valley Hall effect of sound is proposed further. The extraordinary chirality of valley vortex states, detectable in experiments, may open new possibility in sound manipulations. This is appealing to scalar acoustics that lacks spin degree of freedom inherently. Besides, the valley selection enables a handy way to create vortex matter in acoustics, in which the vortex chirality can be controlled flexibly. Potential applications can be anticipated with the exotic interaction of acoustic vortices with matter, such as to trigger the rotation of the trapped microparticles without contact.
56 citations
TL;DR: In this paper, a metasurface for focusing reflected ultrasonic waves over a wide frequency band of 0.45-0.55 MHz was proposed. But, the focusing mechanism can be attributed to the hyperboloidal reflection phase profile imposed by different depths of concentric grooves on the reflective surface, which exhibits a good linear dependence on frequency over the considered frequency band.
Abstract: We report a metasurface for focusing reflected ultrasonic waves over a wide frequency band of 0.45–0.55 MHz. The broadband focusing effect of the reflective metasurface is studied numerically and then confirmed experimentally using near-field scanning techniques. The focusing mechanism can be attributed to the hyperboloidal reflection phase profile imposed by different depths of concentric grooves on the metasurface. In particular, the focal lengths of the reflective metasurface are extracted from simulations and experiments, and both exhibit good linear dependence on frequency over the considered frequency band. The proposed broadband reflective metasurface with tunable focal length has potential applications in the broad field of ultrasonics, such as ultrasonic tomographic imaging, high intensity focused ultrasound treatment, etc.
54 citations
TL;DR: In this paper, an effective metasurface design for constructing two-dimensional acoustic half-Bessel (HB) beams is proposed based on an array of spatially varied coiling-slit units, each of which mimics the wave responses derived from the analytical expression of the acoustic HB beam.
Abstract: Unlike the well-known Airy beams that can be deformed beyond paraxial angles, the half-Bessel (HB) Beams can bend to steeper angles. Here we propose an effective metasurface design for constructing two-dimensional acoustic HB beams. The design is based on an array of spatially varied coiling-slit units, each of which mimics the wave responses derived from the analytical expression of the acoustic HB beam. A tradeoff method is utilized here to simplify the variable amplitude responses. The full-wave simulations and experimental measurements consistently manifest the effectiveness of this design process. Potential applications, such as the large-angle bending transport of particles, can be anticipated.
12 citations
TL;DR: In this article, an analytical expression of the acoustic interaction force among multiple well-separated spherical particles trapped in the same node or antinode plane of a standing wave is derived, which is accurate even for the particles beyond the Rayleigh limit.
Abstract: In this work, we study the acoustically mediated interaction forces among multiple well-separated spherical particles trapped in the same node or antinode plane of a standing wave. An analytical expression of the acoustic interaction force is derived, which is accurate even for the particles beyond the Rayleigh limit. Interestingly, the multi-particle system can be decomposed into a series of independent two-particle systems described by pairwise interactions. Each pairwise interaction is a long-range interaction, as characterized by a soft oscillatory attenuation (at the power exponent of n = −1 or −2). The vector additivity of the acoustic interaction force, which is not well expected considering the nonlinear nature of the acoustic radiation force, is greatly useful for exploring a system consisting of a large number of particles. The capability of self-organizing a big particle cluster can be anticipated through such acoustically controllable long-range interaction.
10 citations
TL;DR: In this paper, the couplings of dipolar modes in adjoining steel cylinders were investigated, and couplings between the quadruple modes when they are closer were found to be the cause of non-leaky surface acoustic waves.
Abstract: In this paper, we systematically investigate a kind of highly localized nonleaky surface acoustic waves (SAWs) in a simple system consisting of a monolayer array of disjunct steel cylinders immersed in water. It shows that the nonleaky SAWs can be attributed to the couplings of the dipolar modes in adjoining steel cylinders, and the couplings of the quadruple modes in adjoining steel cylinders when they are closer. When the SAWs are excited within a finite system, beat patterns are formed, and the cause is analyzed. All the experiments show excellent agreement with the theoretical predictions. This kind of nonleaky SAWs may find potential applications in lab-on-chip devices and acoustic sensors.
9 citations
TL;DR: In this paper, an analytical expression of the acoustic interaction force among multiple well-separated spherical particles trapped in the same node or antinode plane of a standing wave is derived, which is accurate even for the particles beyond the Rayleigh limit.
Abstract: In this work, we study the acoustically mediated interaction forces among multiple well-separated spherical particles trapped in the same node or antinode plane of a standing wave. An analytical expression of the acoustic interaction force is derived, which is accurate even for the particles beyond the Rayleigh limit. Interestingly, the multi-particle system can be decomposed into a series of independent two-particle systems described by pairwise interactions. Each pairwise interaction is a long-range interaction, as characterized by a soft oscillatory attenuation (at the power exponent of n=-1 or -2). The vector additivity of the acoustic interaction force, which is not well expected considering the nonlinear nature of the acoustic radiation force, is greatly useful for exploring a system consisting of a large number of particles. The capability of self-organizing a big particle cluster can be anticipated through such acoustically controllable long-range interaction.
2 citations