Highly sensitive microphones based on large freestanding reduced graphene oxide membranes

Highly sensitive acoustic sensing devices are essential for human‒machine interfaces and modern advanced artificial intelligence (AI) technology. Two-dimensional (2D) materials exhibiting atomically thin thickness and superior mechanical properties are, in principle, ideal membranes for ultimate acoustic sensing. In this work, we present an ultrasensitive microphone using large freestanding reduced graphene oxide (rGO) membranes. The membranes were suspended by a designed pressure-assisted double transfer strategy, resulting in a diameter-to-thickness ratio of ~ 10⁶ (diameter of 8 cm, thin thickness of 80 nm). They exhibit a static pressure responsivity of ~ 500 μm/Pa, and a dynamic signal-to-noise ratio up to ~ 115 dB at 1 kHz. Notably, a rGO-based broadband microphone (100 Hz‒50 kHz) demonstrates a superior language recognition accuracy (90% vs. 70%) compared to that of commercial micro-electromechanical system (MEMS) microphones at a distance of 9 m. Our work provides a reliable route for fabricating large freestanding ultrathin membranes and will promote the development of advanced acoustic devices.