@article{gerard_cui_shen_xie_cummer_zheng_jing_2019, title={Fabrication and experimental demonstration of a hybrid resonant acoustic gradient index metasurface at 40 kHz}, volume={114}, ISSN={["1077-3118"]}, url={http://dx.doi.org/10.1063/1.5095963}, DOI={10.1063/1.5095963}, abstractNote={Over the past few years, acoustic gradient index metasurfaces (GIMs) have been actively studied for the numerous wave control capabilities that they facilitate. Previous research, however, has primarily focused on GIMs that operate in the audible frequency range, due to the difficulties in fabricating such intricate structures at the millimeter and submillimeter scales, for ultrasonic applications. In this work, we design, fabricate, and experimentally demonstrate the working of a hybrid resonant acoustic gradient index metasurface for airborne ultrasound at 40 kHz. The fabrication of such a GIM is made possible by projection microstereolithography, an emerging additive manufacturing technique. Numerical simulations were conducted to verify the metasurface design, and experiments were performed to corroborate these simulations. The stronger dissipation associated with airborne ultrasound is highlighted in this paper. The experimental demonstration of such a metasurface for airborne ultrasound could further its prospects as a candidate for miniaturized acoustic devices.Over the past few years, acoustic gradient index metasurfaces (GIMs) have been actively studied for the numerous wave control capabilities that they facilitate. Previous research, however, has primarily focused on GIMs that operate in the audible frequency range, due to the difficulties in fabricating such intricate structures at the millimeter and submillimeter scales, for ultrasonic applications. In this work, we design, fabricate, and experimentally demonstrate the working of a hybrid resonant acoustic gradient index metasurface for airborne ultrasound at 40 kHz. The fabrication of such a GIM is made possible by projection microstereolithography, an emerging additive manufacturing technique. Numerical simulations were conducted to verify the metasurface design, and experiments were performed to corroborate these simulations. The stronger dissipation associated with airborne ultrasound is highlighted in this paper. The experimental demonstration of such a metasurface for airborne ultrasound could furthe...}, number={23}, journal={APPLIED PHYSICS LETTERS}, author={Gerard, Nikhil J. R. K. and Cui, Huachen and Shen, Chen and Xie, Yangbo and Cummer, Steven and Zheng, Xiaoyu and Jing, Yun}, year={2019}, month={Jun} }
 @article{li_shen_xie_li_wang_cummer_jing_2017, title={Tunable Asymmetric Transmission via Lossy Acoustic Metasurfaces}, volume={119}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.119.035501}, abstractNote={In this study, we show that robust and tunable acoustic asymmetric transmission can be achieved through gradient-index metasurfaces by harnessing judiciously tailored losses. We theoretically prove that the asymmetric wave behavior stems from loss-induced suppression of high order diffraction. We further experimentally demonstrate this novel phenomenon. Our findings could provide new routes to broaden applications for lossy acoustic metamaterials and metasurfaces.}, number={3}, journal={PHYSICAL REVIEW LETTERS}, author={Li, Yong and Shen, Chen and Xie, Yangbo and Li, Junfei and Wang, Wenqi and Cummer, Steven A. and Jing, Yun}, year={2017}, month={Jul} }
 @article{xie_shen_wang_li_suo_popa_jing_cummer_2016, title={Acoustic Holographic Rendering with Two-dimensional Metamaterial-based Passive Phased Array}, volume={6}, ISSN={["2045-2322"]}, DOI={10.1038/srep35437}, abstractNote={Acoustic holographic rendering in complete analogy with optical holography are useful for various applications, ranging from multi-focal lensing, multiplexed sensing and synthesizing three-dimensional complex sound fields. Conventional approaches rely on a large number of active transducers and phase shifting circuits. In this paper we show that by using passive metamaterials as subwavelength pixels, holographic rendering can be achieved without cumbersome circuitry and with only a single transducer, thus significantly reducing system complexity. Such metamaterial-based holograms can serve as versatile platforms for various advanced acoustic wave manipulation and signal modulation, leading to new possibilities in acoustic sensing, energy deposition and medical diagnostic imaging.}, journal={SCIENTIFIC REPORTS}, author={Xie, Yangbo and Shen, Chen and Wang, Wenqi and Li, Junfei and Suo, Dingjie and Popa, Bogdan-Ioan and Jing, Yun and Cummer, Steven A.}, year={2016}, month={Oct} }
 @article{shen_xie_li_cummer_jing_2016, title={Asymmetric acoustic transmission through near-zero-index and gradient-index metasurfaces}, volume={108}, ISSN={["1077-3118"]}, DOI={10.1063/1.4953264}, abstractNote={We present a design of acoustic metasurfaces yielding asymmetric transmission within a certain frequency band. The design consists of a layer of gradient-index metasurface and a layer of low refractive index metasurface. Incident waves are controlled in a wave vector dependent manner to create strong asymmetric transmission. Numerical simulations show that the approach provides high transmission contrast between the two incident directions within the designed frequency band. This is further verified by experiments. Compared to previous designs, the proposed approach yields a compact and planar device. Our design may find applications in various scenarios such as noise control and therapeutic ultrasound.}, number={22}, journal={APPLIED PHYSICS LETTERS}, author={Shen, Chen and Xie, Yangbo and Li, Junfei and Cummer, Steven A. and Jing, Yun}, year={2016}, month={May} }
 @article{shen_jing_2016, title={Loss-induced Enhanced Transmission in Anisotropic Density-near-zero Acoustic Metamaterials}, volume={6}, ISSN={["2045-2322"]}, DOI={10.1038/srep37918}, abstractNote={Abstract Anisotropic density-near-zero (ADNZ) acoustic metamaterials are investigated theoretically and numerically in this paper and are shown to exhibit extraordinary transmission enhancement when material loss is induced. The enhanced transmission is due to the enhanced propagating and evanescent wave modes inside the ADNZ medium thanks to the interplay of near-zero density, material loss, and high wave impedance matching in the propagation direction. The equi-frequency contour (EFC) is used to reveal whether the propagating wave mode is allowed in ADNZ metamaterials. Numerical simulations based on plate-type acoustic metamaterials with different material losses were performed to demonstrate collimation and subwavelength imaging enabled by the induced loss in ADNZ media. This work provides a different way for manipulating acoustic waves.}, journal={SCIENTIFIC REPORTS}, author={Shen, Chen and Jing, Yun}, year={2016}, month={Nov} }
 @article{huang_shen_jing_2016, title={Membrane- and plate-type acoustic metamaterials}, volume={139}, ISSN={["1520-8524"]}, DOI={10.1121/1.4950751}, abstractNote={Over the past decade there has been a great amount of research effort devoted to the topic of acoustic metamaterials (AMMs). The recent development of AMMs has enlightened the way of manipulating sound waves. Several potential applications such as low-frequency noise reduction, cloaking, angular filtering, subwavelength imaging, and energy tunneling have been proposed and implemented by the so-called membrane- or plate-type AMMs. This paper aims to offer a thorough overview on the recent development of membrane- or plate-type AMMs. The underlying mechanism of these types of AMMs for tuning the effective density will be examined first. Four different groups of membrane- or plate-type AMMs (membranes with masses attached, plates with masses attached, membranes or plates without masses attached, and active AMMs) will be reviewed. The opportunities, limitations, and challenges of membrane- or plate-type AMMs will be also discussed.}, number={6}, journal={JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA}, author={Huang, Tai-Yun and Shen, Chen and Jing, Yun}, year={2016}, month={Jun}, pages={3239–3249} }
 @article{huang_shen_jing_2016, title={On the evaluation of effective density for plate- and membrane-type acoustic metamaterials without mass attached}, volume={140}, ISSN={["1520-8524"]}, DOI={10.1121/1.4960590}, abstractNote={The effective densities of plate- and membrane-type acoustic metamaterials (AMMs) without mass attached are studied theoretically and numerically. Three models, including the analytic model (based on the plate flexural wave equation and the membrane wave equation), approximate model (under the low frequency approximation), and the finite element method (FEM) model, are first used to calculate the acoustic impedance of square and clamped plates or membranes. The effective density is then obtained using the resulting acoustic impedance and a lumped model. Pressure transmission coefficients of the AMMs are computed using the obtained densities. The effect of the loss from the plate is also taken into account. Results from different models are compared and good agreement is found, particularly between the analytic model and the FEM model. The approximate model is less accurate when the frequency of interest is above the first resonance frequency of the plate or membrane. The approximate model, however, provides simple formulae to predict the effective densities of plate- or membrane-type AMMs and is accurate for the negative density frequency region. The methods presented in this paper are useful in designing AMMs for manipulating acoustic waves.}, number={2}, journal={JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA}, author={Huang, Tai-Yun and Shen, Chen and Jing, Yun}, year={2016}, month={Aug}, pages={908–916} }
 @article{shen_xie_sui_wang_cummer_jing_2015, title={Broadband Acoustic Hyperbolic Metamaterial}, volume={115}, ISSN={["1079-7114"]}, DOI={10.1103/physrevlett.115.254301}, abstractNote={In this Letter, we report on the design and experimental characterization of a broadband acoustic hyperbolic metamaterial. The proposed metamaterial consists of multiple arrays of clamped thin plates facing the y direction and is shown to yield opposite signs of effective density in the x and y directions below a certain cutoff frequency, therefore, yielding a hyperbolic dispersion. Partial focusing and subwavelength imaging are experimentally demonstrated at frequencies between 1.0 and 2.5 kHz. The proposed metamaterial could open up new possibilities for acoustic wave manipulation and may find usage in medical imaging and nondestructive testing.}, number={25}, journal={PHYSICAL REVIEW LETTERS}, author={Shen, Chen and Xie, Yangbo and Sui, Ni and Wang, Wenqi and Cummer, Steven A. and Jing, Yun}, year={2015}, month={Dec} }
 @article{shen_xu_fang_jing_2014, title={Anisotropic Complementary Acoustic Metamaterial for Canceling out Aberrating Layers}, volume={4}, ISSN={["2160-3308"]}, DOI={10.1103/physrevx.4.041033}, abstractNote={In this paper, we investigate a type of anisotropic, acoustic complementary metamaterial (CMM) and its application in restoring acoustic fields distorted by aberrating layers. The proposed quasi two-dimensional (2D), nonresonant CMM consists of unit cells formed by membranes and side branches with open ends. Simultaneously, anisotropic and negative density is achieved by assigning membranes facing each direction (x and y directions) different thicknesses, while the compressibility is tuned by the side branches. Numerical examples demonstrate that the CMM, when placed adjacent to a strongly aberrating layer, could acoustically cancel out that aberrating layer. This leads to dramatically reduced acoustic field distortion and enhanced sound transmission, therefore virtually removing the layer in a noninvasive manner. In the example where a focused beam is studied, using the CMM, the acoustic intensity at the focus is increased from 28% to 88% of the intensity in the control case (in the absence of the aberrating layer and the CMM). The proposed acoustic CMM has a wide realm of potential applications, such as cloaking, all-angle antireflection layers, ultrasound imaging, detection, and treatment through aberrating layers.}, number={4}, journal={PHYSICAL REVIEW X}, author={Shen, Chen and Xu, Jun and Fang, Nicholas X. and Jing, Yun}, year={2014}, month={Nov} }
 @article{shen_jing_2014, title={Side branch-based acoustic metamaterials with a broad-band negative bulk modulus}, volume={117}, ISSN={["1432-0630"]}, DOI={10.1007/s00339-014-8603-0}, number={4}, journal={APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING}, author={Shen, Chen and Jing, Yun}, year={2014}, month={Dec}, pages={1885–1891} }