University of Exeter
Physics and Astronomy

Imagine being able to manipulate vibrational elastic waves at will with a compact, passive device. The implications of wave control with such a device would range across multiple scales: from surface acoustic wave devices (ubiquitous in electronic circuitry present in mobile devices) through domestic noise control (for example silencing noisy appliances and environmental noise) all the way up to vibration isolation in civil engineering structures, from bridges to buildings. Moreover, such a device offers the potential to recycle and harvest wasted vibrational energy present in our surroundings.

Metamaterials are composite, structured materials which provide promise for such capabilities. These artificial materials have properties which depend on their underlying substructure (often periodic) rather than their chemical composition. There have been significant advances in the design and development of these exotic materials, particularly in the fields of optics and acoustics, where unprecedented wave control has allowed science-fiction-like invisibility cloaks to be realised. This research proposal looks to advance elastic metamaterial counterparts to such devices, leveraging the additional physics present in the elastic system to design, simulate and fabricate devices with a host of vibration control capabilities.

Neither acoustic nor electromagnetic waves have the additional complications of elastic waves, that is, having both shear and compressional bulk waves with independent wave speeds, mode coupling at interfaces, torsional waves, and Rayleigh surface waves. Taking inspiration from electromagnetism, this proposal shall focus on developing elastic metamaterials, particularly to exploit the additional degrees of freedom associated with rotational wave motion present in elastic media.

The nature of the proposed research is inherently multidisciplinary and shall be at the forefront of the boundaries between physics, applied mathematics and engineering. As such it will encompass a range of techniques including mathematical modelling, computational simulation, and experimentation, with a particular focus on ultrasonic devices for energy harvesting and mode conversion.