Adaptive Metamaterials for Ultrasonic Applications

Supervisor: Prof James Windmill & Dr Joseph Jackson

This PhD project will investigate using adaptive metamaterials to manipulate ultrasound. An acoustic metamaterial can be designed to control, direct and affect sound. This is usually done through careful design of the material’s structure and composition. The material can then be used to change sound waves in unusual ways, thanks to properties such as negative effective density and negative bulk modulus. The project will involve a combination of computer modelling, 3D printing to create ultrasonic metamaterials, and experimental acoustic characterization, utilizing techniques and expertise developed at University of Strathclyde.

Acoustic metamaterials structures are often based on Helmholtz resonators and membranes. These typically allow a narrow frequency band to be attenuated, and so acoustic metamaterials based on multiple resonators/membranes have also been investigated. However, this requires larger and larger structures, not suitable for small-scale applications. An alternative solution consists of using structures that present more than one resonance. Work at Strathclyde has shown that additive manufacturing can be an efficient method to obtain this kind of metamaterial, since it allows the fabrication of complex shapes and the use of different materials in the same build.

In this project, the student will develop small-scale 3D printed ultrasonic metamaterials based on combinations of Helmholtz resonators and membranes, capable of generating frequency band gaps where the sound is attenuated. The project will incorporate piezoelectric materials to increase the functionality of the metamaterials through for example adaptive tuning of resonances, and the incorporation of sensory elements into the metamaterial structure. This PhD research work will thus seek to produce highly sensitive ultrasonic sensors.