Ultrasonic metamaterials with negative modulus

Abstract

A new class of ultrasonic metamaterials is finding different applications as their negative dynamic modulus leads to near to surface states with very large wavevectors. These materials have strong dispersive characteristics of elastic modulus with subwavelength resonant structural units, which leads to a bulk mode propagating in the cluster of the units with group velocity antiparallel to the phase advancement. A set of underwater ultrasonic transmission experiments were carried out on one dimensional daisy-chained samples to characterize the unique propagation properties of acoustic waves in the ultrasonic metamaterials. The negative modulus can introduce resonant surface modes, which have very large wavevectors at the interface between two materials of opposite signs of modulus. The artificial ultrasonic metamaterials offer many opportunities in acoustic imaging below the diffraction limit.