Fabricating and Assembling Acoustic Metamaterials and Phononic Crystals

Abstract

Acoustic metamaterials (AMMs) and phononic crystals (PCs) have garnered significant attention in recent years, as part of the collective driving force toward creating intelligent acoustic devices. Advancements in these fields have greatly enhanced the way we manipulate sound waves through transmission, reflection, refraction, absorption, diffraction, or attenuation. In the past decade, AMMs and PCs have enabled novel applications such as acoustic lensing, [1-3] cloaking, [4] levitation, [5] and holography. [6-8] While these exotic structures have been well explored through theoretical and numerical analysis, [9-13] their physical realization is an important topic that is rarely discussed. Considering the ubiquity of sound and the powerful capabilities of AMMs and PCs, the impact of these acoustic structures could be phenomenal. Across the full acoustic frequency spectrum, practical applications such as noise cancellation, [14] underwater detection, [15] medical imaging, [16] and energy harvesting [17,18] could benefit key sectors in our society like healthcare, well-being, environmental sustainability, and security. Moreover, AMMs and PCs can help to usher in next-generation technologies for personalized, immersive multisensory [19-22] experiences. The manipulation of sound can enrich the way we communicate and interact with our surroundings, not simply through audio, but also through tactile sensations. In the future, AMMs and PCs could be used in virtual reality (VR) setups, [23] compact wearable devices, and dynamic midair volumetric displays [24] that are controllable and capable of providing haptic feedback. [25] Beyond the notion that AMMs and PCs can replace phased arrays, they could readily complement one another for more precise control. In commercial devices, AMM and PC functionalities could even be combined together in different ways, e.g., transmissive and sound absorptive structures, for improved performance. To unlock the full potential of AMMs and PCs, it is therefore vital to ensure that practical, physical realization is pursued alongside theoretical investigation in the development of viable acoustic designs. Building an AMM or PC requires some form of fabrication or assembly or both. Fabrication refers to the technologies and processes used to manufacture an object, whereas assembly refers to the strategic amalgamation of parts for a constructive purpose.

Measurement of the ultrasound attenuation and dispersion in 3D-printed photopolymer materials from 1 to 3.5 MHz

“…However, in recent years, the increasing ubiquity and quality of 3D printing has facilitated the development of a variety of different acoustic meta-materials and lenses as a cheaper alternative. 5,6 One such approach is the generation of acoustic holograms. 7 These are 3D-printed phase plates that are able to map the continuous wave output of a singleelement transducer or array onto a pre-defined phase map via variations in sound speed and thickness.…”

Electrically Induced Liquid Metal Droplet Bouncing

“… 10 Electrowetting has been explored with various liquid metals, 11 including aluminum, 12 gallium, 13 and mercury. 14 Eutectic gallium–indium alloy (EGaIn) has emerged as one of the most viable liquid metals because of its extraordinary properties such as excellent fluidity, low melting point, high conductivity, and low toxicity, marking it a promising candidate for applications such as flexible electronics, 15 microfluidic acoustic metamaterials, 16 , 17 and conductive printing. 18 The electrowetting of EGaIn has also been researched by controlling the surface tension of the liquid metal for active droplet manipulation.…”

“…Electrowetting has been explored with various liquid metals, including aluminum, gallium, and mercury . Eutectic gallium–indium alloy (EGaIn) has emerged as one of the most viable liquid metals because of its extraordinary properties such as excellent fluidity, low melting point, high conductivity, and low toxicity, marking it a promising candidate for applications such as flexible electronics, microfluidic acoustic metamaterials, , and conductive printing . The electrowetting of EGaIn has also been researched by controlling the surface tension of the liquid metal for active droplet manipulation. ,, However, the electrowetting actuation of liquid metals is to date limited to the in-plane manipulation of a droplet on an electrically controlled substrate. − Recently, liquid metal droplet jump from a surface has been explored using electrochemical surface reactions and by the contact of solid metal particles with liquid metal droplets in an electrolyte solution .…”

Tailoring Structure‐Borne Sound through Bandgap Engineering in Phononic Crystals and Metamaterials: A Comprehensive Review

“…Compared to acoustic functional materials for controlling air-borne sound, our review paper is motivated by the fact that elastic wave functional materials cater to an entirely different set of applications such as SAW-devices, optomechanics, plate-type devices, seismic shielding, etc. For recent review papers on acoustic functional materials for controlling air-borne sound, the reader may refer to the works of Liu et al, [167] Choi et al [168] and Liao et al [169] Section 2 of this review paper describes the main historical works on PnCs and metamaterials with focus on the physics of BG opening. Then, Section 3 discusses the important achievements on the structural design of PnCs and elastic metamaterials while summarizing different routes for enlarging the elastic BG for different application purposes.…”