Fabrication and experimental demonstration of a hybrid resonant acoustic gradient index metasurface at 40 kHz

Abstract

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.

Design and Fabrication of Negative-Refractive-Index Metamaterial Unit Cells for Near-Megahertz Enhanced Acoustic Transmission in Biomedical Ultrasound Applications

“…The average values and standard deviations are computed based upon the differences between the four nominally identical samples of each membrane type. By decreasing the membrane width to 39 μm and increasing its residual stress to 1.2 GPa, we are able to measure a fundamental membrane resonance at 1.24 MHz, approaching the working frequency range for biomedical ultrasound technologies [30,42,43]. The observed variations in the frequency response may be reduced by improving fabrication and alignment of the unit cells.…”

Observation of Ultrabroadband Acoustic Focusing Based on V‐Shaped Meta‐Atoms

“…Different from other mechanisms, the focusing effect of this type of lens is attributed to phase manipulation, in which the lens is designed by an array of phased unit cells, such as the coiling-up structures, [31,36,37] labyrinthine structures, [32,38,39] and Helmholtz resonators. [40][41][42][43] However, the phase manipulation of these focusing lenses is realized by adjusting the parameters of each unit cell, and thus the working bandwidth of the designed lenses is generally narrow. By introducing the unit cells with different ratios of argon and xenon, [44,45] or those with air of different temperatures, [46,47] the broadband focusing lenses can be realized because of the matched impedances between two media.…”

Dispersion tuning and route reconfiguration of acoustic waves in valley topological phononic crystals

“…Moreover, by reducing both the lattice constant and cavity depth, miniaturized PCs could be developed for controlling ultrasonic waves. Such devices could be fabricated by advanced manufacturing techniques, such as replication-based forming [54][55][56] , high-resolution additive manufacturing [57][58][59] , and/or micromilling 60,61 . It should also be possible to reduce the response time of the system through automatic operation.…”