Acoustic-elastic metamaterials and phononic crystals for energy harvesting: a review

Metamaterials and phononic crystals (PCs) with artificially designed periodic microstructures have attracted increasing research interests due to their unique properties that cannot be easily realized in natural materials. In recent years, the applications of metamaterials and PCs have been extended into the field of energy harvesting. A direct integration design strategy can yield a multifunctional system to suppress undesired vibrations/noise and convert them into electrical energy for providing power supply to widely distributed micro-electromechanical systems. Moreover, the defect state mode of metamaterials/PCs can localize the energy with an amplification effect, which has a great potential for improving energy harvesting efficiency. In addition, through tailoring the refractive index profile of metamaterials/PCs, the wave focusing phenomenon can be realized to boost the energy harvesting efficiency over a wide frequency range. This paper presents a comprehensive overview of the state-of-the-art advances in this direction over the past decade. According to the design strategies and working mechanisms, the existing studies in the literature on this topic are outlined and classified into three different categories. The advantages and disadvantages of various configurations are compared. The potential solutions to the existing drawbacks are discussed. An outlook on future prospects in this area is provided.