Additive Manufacture of Small-Scale Metamaterial Structures for Acoustic and Ultrasonic Applications

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.

Additive Manufacturing in Atomic Layer Processing Mode

“…However, so far the resolution (the smallest feature size controllable) has been on the order of hundreds of micrometers, although the integration of nanostructures into 3D-printed materials or patterns is possible. [9][10][11][12][13][14][15][16][17][18] In other words, 3D printing is several orders of magnitude away from the feature sizes accessible by lithographic methods. In summary, 3D printing has the direct pattern generation capability and materials versatility, whereas Additive manufacturing (3D printing) has not been applicable to micro-and nanoscale engineering due to the limited resolution.…”

Transmissive Labyrinthine Acoustic Metamaterial‐Based Holography for Extraordinary Energy Harvesting

“…For ultrasonic operation, our subwavelength meta‐bricks were fabricated with high‐resolution three‐dimensional (3D) printing. [ 38 ] The LAM was printed with VeroClear plastic, which allowed it to be light and portable (see Experimental section). The elements within the meta‐brick and the position of each meta‐brick inside the LAM were chosen based on the required analog phase map built using the Gechberg–Saxton (GS) algorithm and piston model.…”

Enhanced sound absorption properties of porous ceramics modified by graphene oxide films

“…Therefore, acoustic metamaterials, like other resonant structures, are narrow‐band in nature. Moreover, the manufacture of acoustic metamaterials is too trivial to be widely used 32 . Notably, several scholars have improved the noise reduction performance of porous materials by setting a thin film material behind porous sound‐absorbing material or combining graphene oxide (GO) with porous polymers 33–38 …”

“…Moreover, the manufacture of acoustic metamaterials is too trivial to be widely used. 32 Notably, several scholars have improved the noise reduction performance of porous materials by setting a thin film material behind porous sound-absorbing material or combining graphene oxide (GO) with porous polymers. [33][34][35][36][37][38] To enhance low-frequency absorption and keep the noise reduction coefficient (NRC) up, a comprehensive application of multiple sound absorption mechanisms is required.…”