Fabricating and Assembling Acoustic Metamaterials and Phononic Crystals
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, cloaking, levitation, and holography. While these exotic structures have been well explored through theoretical and numerical analysis, 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, underwater detection, medical imaging, and energy harvesting 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 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, compact wearable devices, and dynamic midair volumetric displays that are controllable and capable of providing haptic feedback. 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. AMMs and PCs can also be assembly free, i.e. the complete C. Choi, Dr. S. Bansal, Prof. S. Subramanian Department of Computer Science Faculty of Engineering University College London London WC1E 6BT, UK E mail: shubhi.bansal@ucl.ac.uk; s.subramanian@ucl.ac.uk Prof. N. Munzenrieder Faculty of Science and Technology Free University of Bozen Bolzano Bozen 39100, Italy