Tailoring Wave Propagation in Acoustic Metamaterial: From Attenuation to Localization

Abstract

Wave motion, one of the most common physical phenomena in daily life, can be either beneficial or detrimental to human beings and their properties. The utilization of energy and information carried by waves is a key advance of modern human civilization, which provides significant convenience for human life. However, the real-life environment is inundated with unwanted noise waves that are generated by nature or human activities. Acoustic metamaterials (AM), including phononic crystals, have revolutionized wave manipulation through artificially engineered microstructures, enabling unprecedented control over elastic and sound waves. These materials exhibit unique properties such as bandgap formation, wave localization, and waveguiding, which are unattainable in natural materials. This doctoral dissertation comprehensively explores the fundamental mechanisms, including Bragg scattering and local resonance mechanism, and highlights advanced techniques for bandgap widening, such as multi-band resonance. Furthermore, the integration of topological phases into AMs has led to the development of topological acoustic metamaterials (TAMs). The induced topologically protected edge/interface states, which feature conductive and robust wave transportation at edge or interface of two domains with different topological phases but insulation for bulk, supports robust wave propagation and energy localization at edges or interfaces. Further exploration of high-order TAMs breaks bulk-edge correspondence and achieves energy localization at lower dimensions i.e., corners of 2D TAM and edges of 3D TAM. Employment of accidental Dirac cones achieves polarization- or frequency-dependent wave demultiplexing. Advancements in actively controllable AMs are also studied, leveraging mechanically reconfigurable structures to achieve real-time tunability. In conclusion, the studies enable wave manipulation through bandgap engineering, topological states, and mechanical tunability, validated via theoretical modeling, numerical simulation, and experiment.

Date of Award	4 Aug 2025
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	C W LIM (Supervisor)