One already available method to expand the range of material properties is to adjust the composition of materials at the molecular level using chemistry. We would like to develop the alternative approach of homogenization which broadens the definition of a material to include artificially structured media (fluids and solids) in which the effective electromagnetic, hydrodynamic or elastic responses result from a macroscopic patterning or arrangement of two or more distinct materials. This project will explore the latter avenue in order to markedly enhance control of surface water waves and elastodynamic waves propagating within artificially structured fluids and solid materials, thereafter called acoustic metamaterials.
Pendry's perfect lens, the paradigm of electromagnetic metamaterials, is a slab of negative refractive index material that takes rays of light and causes them to converge with unprecedented resolution. This flat lens is a combination of periodically arranged resonant electric and magnetic elements. We will draw systematic analogies with resonant mechanical systems in order to achieve similar control of hydrodynamic and elastic waves. This will allow us to extend the design of metamaterials to acoustics to go beyond the scope of Snell-Descartes' laws of optics and Newton's laws of mechanics.
Acoustic metamaterials allow the construction of invisibility cloaks for non-linear surface water waves (e.g. tsunamis) propagating in structured fluids, as well as seismic waves propagating in thin structured elastic plates.
Maritime and civil engineering applications are in the protection of harbours, off-shore platforms and anti-earthquake passive systems. Acoustic cloaks for an enhanced control of pressure waves in fluids will be also designed for underwater camouflaging.
Light and sound interplay will be finally analysed in order to design controllable metamaterials with a special emphasis on undetectable microstructured fibres (acoustic wormholes).
Fields of science
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