Kim, Sangtae Choi, Jaehoon Seung, Hong Min Jung, Inki Ryu, Ki Hoon Song, Hyun-Cheol Kang, Chong-Yun Kim, Miso 2024-01-19T11:02:58Z 2024-01-19T11:02:58Z 2022-08-04 2022-10 2211-2855 https://pubs.kist.re.kr/handle/201004/114528 Acoustic energy harvesting (AEH) has emerged as a promising powering process for the sustainable self-powered operation of wireless sensors in wearable, biomedical, and industrial applications. However, despite the abundance of sound sources in the environment, intrinsically low acoustic energy density still poses a critical challenge; therefore, the development of various sound amplification structures, such as Helmholtz resonators (HRs), phononic crystals, and acoustic metamaterials is required. In this study, we combined two distinct sound amplification mechanisms, Helmholtz resonance and omnidirectional acoustic wave focusing, to generate a sufficiently high power output within an ambient sound environment at practically low frequencies (< 1 kHz). A two-degree-of-freedom model was developed to systematically design a HR integrated with a piezoelectric device (HR-PEH). Subsequently, the HR-PEH was incorporated with a circularly symmetric gradient index phononic crystal (GRIN PnC) structure that enabled omnidirectional sound focusing. Finally, we constructed a coupled acoustic system GRIN-HR-PEH. Analytical modeling and experimental characterization revealed the existence of two distinct dual operating frequencies for power maximization: mechanical and acoustic resonances, which offers design flexibility in coupled AEH systems. As a result, the coupled GRIN-HR-PEH system yielded an output power of up to 4.1 mW under an ambient incident sound pressure of 47 dB, satisfying the power requirements of practical applications. English Elsevier BV Gradient-index phononic crystal and Helmholtz resonator coupled structure for high-performance acoustic energy harvesting Article 10.1016/j.nanoen.2022.107544 1 Nano Energy, v.101 Nano Energy 101 N scie scopus 000827326600002 Chemistry, Physical Nanoscience & Nanotechnology Materials Science, Multidisciplinary Physics, Applied Chemistry Science & Technology - Other Topics Materials Science Physics Article FREQUENCY Helmholtz resonator Gradient -index phononic crystal Acoustic energy harvesting Piezoelectricity Metamaterials Sound pressure amplification