Abstract
Acoustic metamaterials are large-scale materials with small-scale structures. These structures allow for unusual interaction with propagating sound and endow the large-scale material with exceptional acoustic properties not found in normal materials. However, their multi-scale nature means that the manufacture of these materials is not trivial, often requiring micron-scale resolution over centimetre length scales. In this review, we bring together a variety of acoustic metamaterial designs and separately discuss ways to create them using the latest trends in additive manufacturing. We highlight the advantages and disadvantages of different techniques that act as barriers towards the development of realisable acoustic metamaterials for practical audio and ultrasonic applications and speculate on potential future developments.
Highlights
The progression of research concerning the acoustic, vibrational and mechanical behaviour of small-scale structures is closely linked to the status of microfabrication/3D printing technologies [1,2]
This review explores the variety of small-scale acoustic metamaterials (AMM) currently in development, along with the 3D printing methods that show potential to manufacture them
Examples membranes and andperforated perforatedplates, plates,where where displays a uniform structure of hexagonal unit-cells arranged in parallel and sealed by membranes at each open end (Reprinted from [71], metastructure of hexagonal unit-cells arranged in parallel and sealed by membranes at each open end (Reprinted from [71], with the permission of AIP Publishing). (b) shows a perforated thin-plate design with holes drilled at the cross points of with the permission of AIP Publishing). (b) shows a perforated thin-plate design with holes drilled at the cross points of the the resin frame to introduce anti-resonant behaviour [73]
Summary
The progression of research concerning the acoustic, vibrational and mechanical behaviour of small-scale structures is closely linked to the status of microfabrication/3D printing technologies [1,2]. AMMs have yet to be fully realized in commercial applications, with few examples available of their current deployment in industry (primarily based in sound control) [4,5,6] This is in part due to the prohibitive and logistical restrictions in manufacturing these structures; as such, experimental prototypes of AMMs are typically 3D-printed to achieve the required level of precision and size [7]. Micromachines 2021, 12, 634 review, small-scale refers to structures with a minimum feature size of a few millimetres or lower, optimum small features can be within the micro or nanoscales
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