Mutually Reinforced Polymer–Graphene Bilayer Membranes for Energy‐Efficient Acoustic Transduction

Graphene holds promise for thin, ultralightweight, and high‐performance nanoelectromechanical transducers. However, graphene‐only devices are limited in size due to fatigue and fracture of suspended graphene membranes. Here, a lightweight, flexible, transparent, and conductive bilayer composite of polyetherimide and single‐layer graphene is prepared and suspended on the centimeter scale with an unprecedentedly high aspect ratio of 105. The coupling of the two components leads to mutual reinforcement and creates an ultrastrong membrane that supports 30 000 times its own weight. Upon electromechanical actuation, the membrane pushes a massive amount of air and generates high‐quality acoustic sound. The energy efficiency is ≈10–100 times better than state‐of‐the‐art electrodynamic speakers. The bilayer membrane's combined properties of electrical conductivity, mechanical strength, optical transparency, thermal stability, and chemical resistance will promote applications in electronics, mechanics, and optics. To fabricate ultrahigh‐aspect‐ratio, lightweight, and transparent conductive membranes, single‐layer graphene is reinforced by high‐performance polyetherimide to form a laminate bilayer. The bilayer is exceptionally strong, lightweight, transparent, and conductive and has a record‐high aspect ratio of 1 × 105. As an acoustic transducer in a prototype electrostatic speaker, the bilayer consumes 100 times less energy than state‐of‐the‐art electrodynamic speakers.