Gradient-index phononic crystal and Helmholtz resonator coupled structure for high-performance acoustic energy harvesting. (October 2022)

• Record Type: Journal Article
• Authors: Kim, Sangtae; Choi, Jaehoon; Seung, Hong Min; Jung, Inki; Ryu, Ki Hoon; Song, Hyun-Cheol; Kang, Chong-Yun; Kim, Miso
• Is Part Of: Nano energy. Volume 101(2022)
• Publication Date: 2022-10
• Subjects: Helmholtz resonator -- Gradient-index phononic crystal -- Acoustic energy harvesting -- Piezoelectricity -- Metamaterials -- Sound pressure amplification; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2022.107544
• Languages: English
• ISSNs: 2211-2855

Abstract

Graphical Abstract: ga1 Abstract: 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. Highlights: A gradient-index phononic crystal and Helmholtz coupled structure is proposed as a synergistic sound amplification mechanism. The hybrid system exhibits omnidirectional acoustic energy focusing and harvesting capabilities. The proposed system yields a remarkable output power generation of 4.1 mW at a low frequency of 471 Hz.