title: Metamaterial bricks and quantization of meta-surfaces.
abstract: Controlling acoustic fields is crucial in diverse applications such as loudspeaker design, ultrasound imaging and therapy or acoustic particle manipulation. The current approaches use fixed lenses or expensive phased arrays. Here, using a process of analogue-to-digital conversion and wavelet decomposition, we develop the notion of quantal meta-surfaces. The quanta here are small, pre-manufactured three-dimensional units-which we call metamaterial bricks-each encoding a specific phase delay. These bricks can be assembled into meta-surfaces to generate any diffraction-limited acoustic field. We apply this methodology to show experimental examples of acoustic focusing, steering and, after stacking single meta-surfaces into layers, the more complex field of an acoustic tractor beam. We demonstrate experimentally single-sided air-borne acoustic levitation using meta-layers at various bit-rates: from a 4-bit uniform to 3-bit non-uniform quantization in phase. This powerful methodology dramatically simplifies the design of acoustic devices and provides a key-step towards realizing spatial sound modulators.
authors.affiliation: INTERACT Lab, School of Engineering and Informatics, University of Sussex, Brighton BN1 9RH, UK.
authors.forename: Gianluca
authors.identifier: 0000-0003-2578-2814
authors.initials: G
authors.lastname: Memoli
authors.affiliation: Department of Mechanical Engineering, University of Bristol, Bristol BS8 1TR, UK.
authors.forename: Mihai
authors.initials: M
authors.lastname: Caleap
authors.affiliation: INTERACT Lab, School of Engineering and Informatics, University of Sussex, Brighton BN1 9RH, UK.
authors.forename: Michihiro
authors.initials: M
authors.lastname: Asakawa
authors.affiliation: INTERACT Lab, School of Engineering and Informatics, University of Sussex, Brighton BN1 9RH, UK.
authors.forename: Deepak R
authors.initials: DR
authors.lastname: Sahoo
authors.affiliation: Department of Mechanical Engineering, University of Bristol, Bristol BS8 1TR, UK.
authors.forename: Bruce W
authors.initials: BW
authors.lastname: Drinkwater
authors.affiliation: INTERACT Lab, School of Engineering and Informatics, University of Sussex, Brighton BN1 9RH, UK.
authors.forename: Sriram
authors.initials: S
authors.lastname: Subramanian