Resonant attenuation of surface acoustic waves by a weakly bonded layer

TL;DR

This paper demonstrates that a weakly bonded thin layer on a substrate can induce strong, tunable attenuation of surface acoustic waves within specific frequency ranges, mimicking resonant metamaterials without surface structuring.

Contribution

It introduces the concept of adhesion-induced resonant attenuation zones in layered systems, offering a simple, tunable method for SAW manipulation using weak adhesion.

Findings

Attenuation zones are bounded in k-space and resemble resonant behavior.

The phenomenon can be modeled with a mass-spring analogy.

A bilayer configuration with a soft interfacial film can realize this effect experimentally.

Abstract

We investigate the propagation of surface acoustic waves (SAWs) in a layered half-space system comprising a continuous, sub-wavelength-thick layer weakly adhering to a substrate. Using finite element simulations, we demonstrate that this configuration - without requiring surface structuration - gives rise to frequency ranges bounded in k-space and characterized by strong SAW attenuation, which we term adhesion-induced resonant attenuation zones. We show that these attenuation zones closely mimic the resonant behavior typically observed in locally resonant metamaterials and can be understood through a mass-spring analogy, where the adhesion between the layer and substrate governs the frequency and width of the attenuation zones. As a practical demonstration, we propose a bilayer configuration as a practical route to experimentally realize adhesion-induced resonant attenuation of SAWs, where a soft and thin interfacial film serves as an intermediate adhesive bonding between the layer and substrate, providing a realistic and tunable interfacial stiffness. Our findings offer a simplified route to achieving SAW manipulation through continuous layered media with tunable adhesion, providing a practical alternative to complex structural designs in SAW-based devices across a broad frequency range.