Reprogrammable acoustic metamaterials for multiband energy harvesting

Acoustic metamaterials are artificial materials that possess the remarkable ability to control and manipulate acoustic waves, which makes them ideal for acoustic energy harvesting. However, the current limitation is that these metamaterials can only effectively harvest energy within a narrow band defined by a single defect mode. To overcome this challenge, a new type of reprogrammable acoustic metamaterial has been developed. This metamaterial incorporates local resonance and magnetic modulation of the structure to enable multiband piezoelectric energy harvesting. The design of triple-band energy localization and regulation involves the utilization of the Bloch theorem and magnetic dipole model. The Bloch theorem is utilized to investigate the propagation of waves within acoustic metamaterials. Electromechanical conversion is achieved through the direct piezoelectric effect of piezoelectric ceramic. Pressure acoustics, solid mechanics, electrostatics and electrical circuit modules are employed to simulate the coupling effects among sound, mechanical and electrostatic fields for acoustic energy harvesting. The magnetic dipole model is employed to determine the magnetic force between the carbon steel cylinders of reprogrammable acoustic metamaterials and the permanent magnet used for magnetic modulation. The structural resonance of the acoustic metamaterials is in charge of band I from 35 Hz to 60 Hz. The local resonance is in charge of band II from 1650 Hz to 2050 Hz. The synergy between the structural resonance and local resonance contributes to band III from 4800 Hz to 5700 Hz with dominance of the structural resonance. The harvested powers of the acoustic metamaterials are 0.10 mW, 0.23 mW and 0.13 mW for different bands. By utilizing reprogrammable magnetic modulation on the structural resonances, the harvested powers for band I and band III experience remarkable enhancements of 655% and 214%, respectively. This breakthrough has the potential to revolutionize the field of acoustic energy harvesting, enabling the harvesting of energy across a wider range of frequencies. We anticipate that the implementation of the multiband acoustic metamaterial energy harvesting wall will expedite the growth of advanced technologies pertaining to acoustic energy localization and self-powered sensing.