engleski

Graphene acoustic diaphragms

Vibrating diaphragms have become an important component of acoustics technology, with nearly all commercial microphones and speakers of the past half a century relying on diaphragm vibration. Although few select materials (such as nickel and boPET) are predominantly used because of their favorable properties such as small mass density and large tensile strength, the rise of new materials with superior properties such as graphene demands an assessment of their potential use in acoustic diaphragms. Here we evaluate various forms of graphene as an acoustic diaphragm material. We fabricate diaphragms from graphene paper and multilayer (~60 layers) CVD graphene and measure their response to acoustic stimuli either in capacitance mode, which most closely resembles actual use in electrostatic condenser microphones, or with digital holography, which allows for physical studies of diaphragm vibration modes [1]. We find that multilayer graphene diaphragms outperform traditional nickel membranes in terms of responsivity, up to 12 dB at audio frequencies [2]. For large- diameter (25 mm) diaphragms that can be made from graphene paper, we detect a rich array of acoustic vibration modes that point to the diaphragms’ potential use in pressure sensing or for detection of weak acoustic signals in quiet environments. Our findings are supported with numerical COMSOL calculations that also reveal that a thicker multilayer diaphragm made of 300 layers of CVD graphene would in theory sustain tension forces that allow ultrasonic reach. Hence we conclude that graphene diaphragms hold potential for miniature low- cost ultrasonic transducers that compete with current piezoelectric technology.

digital holography, graphene, acoustic diaphragm, COMSOL, microphone, speakers, CVD

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