Integration of Graphene and ZnO Nanowires for a Self-Powered Piezoelectric MEMS Microphone

This paper describes a novel self-powered piezoelectric MEMS microphone utilizing vertically aligned ZnO nanowires coupled with a suspended graphene/PMMA diaphragm. Direct contact between the graphene/PMMA membrane and ZnO nanowires efficiently converts acoustic vibrations into piezoelectric charges, generating measurable output voltages without requiring external bias or complex capacitive structures. The ZnO nanowires (4.5 μm in length), synthesized via a hydrothermal growth method, serve as structural supports and active piezoelectric transducers. Experimental characterization reveals stable linearity across a sound pressure range of 0.02 Pa (60 dB_SPL) to 0.2 Pa (80 dB_SPL) and a broadband acoustic response from 1 kHz to 20 kHz, achieving a peak sensitivity of approximately 3.35 mV/Pa (-49.5 dBV). The proposed integration of graphene and ZnO nanowires offers a simplified, etch-free fabrication process for a MEMS microphone, demonstrating significant promise as a reproducible, high-performance acoustic transducer for next-generation MEMS microphones.