Acoustic Metamaterials Through a Microfluidic, Bottom-up Approach: Toward Highly Attenuating, Negative Effective Density Materials.

摘要

Our initial idea was to build metamaterials with specific properties such as large attenuation capacities in a targeted field of frequencies. If much work has been up to now performed using centimetre-sized handmade mechanical resonators adapted to audible frequencies (1-3), fewer attempts have been made on smaller micro-resonators, in the 100 m range, i.e. for ultrasonic frequencies. Following this path, we recently proposed two different microfluidic approaches to get such micro-resonators: (1) The core-shell approach; (2) The resonant emulsion approach. In the first one, we aimed at fabricating core-shell objects composed of a hard core exhibiting a high density contrast with a surrounding elastic soft shell, the resulting core-shell being finally embedded in a relatively hard solid matrix. In the second approach, one aims at fabricating a material in which the incoming wave will exhibit a 'Mie' type of resonance with the inclusions.