The functionality of thermally active phononic crystals (PnC) and metamaterials can be greatly enhanced by utilizing the temperature-dependent physical characteristics of heat-sensitive materials within the periodic structure. The phase transformation between water and ice occurs within a narrow range of temperatures that can lead to significant changes in its acoustic transmission due to the modification of the elastic properties of periodic phononic structures in an aqueous medium. A phononic crystal with acrylic scatterers in water is designed to function as an acoustic filter, beam splitter, or lensing based on the device’s temperature due to changes in the phase of the ambient medium. The transition from room temperature to freezing point reduces the contrast in acoustic properties between the ice-lattice and the scatterer materials (acrylic) and switches off the metamaterial of the water-based PnC. The numerically simulated equi-frequency contours and wave propagation characteristics demonstrate the switchable meta-material to the periodic phononic structure’s normal behavior due to the phase transition of water. Effects such as Van Hove’s singularity and filamentation-like effects in an acoustic meta-material system can be thermally tuned.
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Simultaneous negative reflection and refraction and reverse-incident right-angle collimation of sound in a solid-fluid phononic crystal
The square lattice phononic crystal (PnC) has been used extensively to demonstrate metamaterial effects. Here, positive and negative refraction and reflection are observed simultaneously due to the presence of Umklapp scattering of sound at the surface of PnC and square-like equifrequency contours (EFCs). It is found that a shift in the EFC of the third transmission band away from the center of the Brillouin zone results in an effectively inverted EFC. The overlap of the EFC of the second and third band produce quasimomentum-matching conditions that lead to multi-refringence phenomena from a single incident beam without the introduction of defects into the lattice. Additionally, the coupling of a near-normal incident wave to a propagating almost perpendicular Bloch mode is shown to lead to strong right-angle redirection and collimation of the incident acoustic beam. Each effect is demonstrated both numerically and experimentally for scattering of ultrasound at a 10-period PnC slab in water environment.
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- Award ID(s):
- 1741677
- NSF-PAR ID:
- 10373827
- Date Published:
- Journal Name:
- The Journal of the Acoustical Society of America
- Volume:
- 151
- Issue:
- 4
- ISSN:
- 0001-4966
- Page Range / eLocation ID:
- 2723 to 2731
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1121/10.0010158
