An Experimental and Theoretical Investigation of Ultrasound Transmission in Bubbly PDMS Phononic Crystals

摘要: Phononic crystals are twoand three-dimensional structures with a periodic arrangement of two or more materials different acoustic properties. Depending on the size, structure, and characteristics constituent materials, meta-materials interesting properties can be formed. These used to control transmission sound at selected frequencies, focus sound, serve as waveguides. In this study, we investigated ultrasonic waves through polydimethylsiloxane (PDMS) films entrapped air bubbles. We examined how PDMS layers engineered by varying dimensions, separation, reproduced previously published data using theoretical models that describe in air-PDMS crystals: (1) simple scattering model for series partially reflective thin films, (2) code MULTEL, which calculates solution multiple theory. then these predict performance new phononic scanning large parameter space. To create structures, first fabricated arrays micron-scale pillars silicon wafer. were cast pillar templates stacked form bubble periodicity. A processes developed stack unprecedented alignment. Finally, measured transducer/receiver setup water bath compared it results. Modeling Ultrasound Transmission: fit experimental [1] single layer square lattice (a = 300 μm) four-layer tetragonal (ax μm; az 350 μm). The analytic approach treats each plane iteratively reflection all [1, 2]. also rigorous theory (MST) [3] where served source incoming waves. found excellent agreement values approaches gave consistent results much Figure 1: Contour plot analytical function radius frequency. N 1, ax μm. frequency range. explore broad space determine variation key parameters (e.g., number layers, separation). 1 demonstrates one such investigation, fixed separation calculated up 5 MHz varied 100 Using similar approach, showed crystal tuned block certain frequencies. blocked followed isolated Minnaert resonance [4]. However, due periodicity, could tune away from adjusting in-plane separation.