The Graphene\nSqueeze-Film Microphone

Most microphones detect sound-pressure-induced motion\nof a membrane.\nIn contrast, we introduce a microphone that operates by monitoring\nsound-pressure-induced modulation of the air compressibility. By driving\na graphene membrane at resonance, the gas, that is trapped in a squeeze-film\nbeneath it, is compressed at high frequency. Since the gas-film stiffness\ndepends on the air pressure, the resonance frequency of the graphene\nis modulated by variations in sound pressure. We demonstrate that\nthis squeeze-film microphone principle can be used to detect sound\nand music by tracking the membrane’s resonance frequency using\na phase-locked loop. The squeeze-film microphone potentially offers\nadvantages like increased dynamic range, lower susceptibility to pressure-induced\nfailure and vibration-induced noise over conventional devices. Moreover,\nmicrophones might become much smaller, as demonstrated in this work\nwith one that operates using a circular graphene membrane with an\narea that is more than 1000 times smaller than that of MEMS microphones.