Integrated acoustic metamaterial triboelectric nanogenerator for joint low-frequency acoustic insulation and energy harvesting

In this study, we present a new device designed to manipulate low-frequency sound waves. The device utilizes the principles of acoustic metamaterials to achieve high-performance sound insulation, while also possessing the capability to convert sound energy into electrical energy. Unlike previous studies on membrane acoustic metamaterials, this device incorporates a membrane component but eliminates the need for precise tension force. The structural parameters of the device are frequency-dependent, allowing for a lightweight design while maintaining satisfactory low-frequency sound insulation performance. At the sound insulation peak frequency, the IAM-TENG exhibits an impressive sound insulation capability of over 30 dB. Moreover, when subjected to bandlimited white noise excitation in the frequency range of 50 Hz-500 Hz, the IAM-TENG showcases a substantial enhancement of nearly 10 dB in sound insulation performance in comparison to a sample of the same weight and size. Additionally, the device achieves a uniform displacement distribution, with large amplitude displacement occurring around the sound transmission dip frequency. Exploiting this property, we have designed a triboelectric nanogenerator (TENG) that can convert incident acoustic energy into electrical energy. This nanogenerator structure utilizes multi-walled carbon nanotubes (MWCNTs) and FEP (Fluorinated Ethylene Propylene) membrane as the triboelectric layers. With an acoustic excitation level of 100 dB at the optimal frequency, the harvested electrical power reaches 0.93 mW. The device has a surface mass density of only 2kg/m2, yet it provides remarkable acoustic insulation performance and can power small-scale electronic devices. These innovative properties have the potential to accelerate the development of self-powered, smart, and multifunctional structures in the Internet of Things era.