Manipulating Acoustic wavefronts using metamaterials for novel user interfaces

Project Information

Interfaces

Grant agreement ID: 787413

DOI

10.3030/787413

Project closed

EC signature date 26 April 2018

Start date 1 May 2018

End date 31 July 2024

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 457 718,00

EU contribution

€ 2 457 718,00

Coordinated by

UNIVERSITY COLLEGE LONDON
United Kingdom

Periodic Reporting for period 5 - Interfaces (Manipulating Acoustic wavefronts using metamaterials for novel user interfaces)

Reporting period: 2023-07-01 to 2024-07-31

Summary of the context and overall objectives of the project

The INTERFACES project explored how sound waves can be shaped and controlled using specially designed materials called acoustic metamaterials. The team developed both static and reconfigurable devices to steer and manipulate sound in real-time. Highlights include the invention of fluid- and magnetically-actuated materials that can adaptively reshape sound fields, and algorithms that enable high-speed 3D acoustic displays—even in complex environments. These breakthroughs have led to new ways of visualising and interacting with data using mid-air particle displays, and to noise control applications, including early work on wind farm noise mitigation. Two start-up companies—AcoustoFab and Metasonixx—were created to take these ideas into the real world, focusing on applications in advanced manufacturing and environmental acoustics. The project has resulted in over 25 high-profile publications and several patents, establishing a foundation for future technologies in interactive displays, adaptive sound environments, and sustainable energy infrastructure.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The main initial progress has been in establishing the research team. My team consists of 3 PhD students, 3 post-docs (some of them part-time) and 3 support staff.

We are currently looking at multiple approaches to designing active and reconfigurable transmissive and reflective metamaterials. Our first approach is based on making the flaps on a labyrinth metamaterial dynamic. The second approach is to use electrowetting to control the movement of a drop of water over a slit. Through early simulations we have established that this tunable slit acoustic metamaterial functions well as a binary metamaterial. We are currently in the process of assembling this device and testing it for different droplet sizes and slit widths.

Finally, we have started exploring the use of multi-rate sampling theory and unitary filter banks to design reflective and transmissive (supra)wavelength metasurfaces that can achieve perfect reconstruction of acoustic fields.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Acoustic meta-cells are the repetitive units of specially engineered materials designed to control, direct and manipulate sound waves for numerous applications like cloaking and ultrasound imaging. The limitation of current metamaterials is the modest passive tunability and narrow operational frequencies offered by existing approaches. Active tunability can be achieved using smart integration of structures and actuation mechanisms. We built a functional microfluidic device based on electrowetting mechanism to achieve a 20 kHz broad spectrum tuneable microfluidic acoustic meta-cell. It consists of a sub-wavelength slit whose length is tuned by moving a liquid droplet over it using electrowetting. Acoustic wave engineering, dealing with programmable switching, continuous amplitude modulation in spatio-temporal space, and dynamic phase-shift of waves is demonstrated both theoretically and experimentally. Our approach is scalable and amenable to the large scale manufacturing of tuneable meta-surfaces, opening strong future opportunities for building spatial sound modulators that can generate complex sound fields.

We are also developing a reconfigurable reflective spatial sound modulator for ultrasonic waves (relates to WP1 and 2) that is able to imprint an on-demand phase signature to an incoming wave. The device is made of 1024 rigidly-ended squared waveguides with sliding bottom surfaces to provide variable phase delays. Experiments demonstrate its ability to focus ultrasonic waves at different points in space and generate accurate pressure holograms at different planes. Moreover, it is theoretically and experimentally demonstrated that the SSM outperforms state-of-the-art phased-array transducers for the generation of sharp focal points and acoustic holograms. This result paves the way for the construction of electronically-controlled reflective spatial sound modulators, in analogy to the commercially available spatial light modulators for light.

Examples of Applications that could be enabled by this project