Dual-band negative index ultrasonic metafluids

摘要: The extraordinary properties of acoustic (random) metamaterials, such as negative refractive index, originate from low frequency resonances sub-wavelength particles. While most these functional materials are fabricated by mechanical engineering, we have recently shown that soft matter techniques coupled with microfluidics open a new synthesis route for metamaterials [1]. As demonstration, achieved 3D ultrasonic metafluids index producing large amounts calibrated porous microspheres, acting like strong Mie resonators [2]. wide variety physico-chemical processes offered chemical engineering allows the full-control mechanical/acoustical parameters (elasticities/celerities) resonant micro-particles. Therefore, number and characteristics (width, depth) “negative bands” can be precisely tuned over broad range. an example, demonstrated it is not only possible to achieve one band [2], but also two separate ones [3]. In this talk, show emergence second due shear waves propagate within micro-beads. they often neglected in theoretical works, wave may induce dipolar transverse resonance leads when overlaps monopolar (longitudinal) resonance. We demonstrate Poisson coefficient, which parametrizes ratio transverse-to-longitudinal sound celerities, relevant parameter anticipate whether or will emerge.