Experimental study of a biomimetic artificial basilar membrane fabricated using piezoelectric micromachined beams

The basilar membrane and hair cells are the main parts of the mammalian cochlea, which converts external sound into bioelectrical signals, in the inner ear. Loss of hair cells on the basilar membrane in the cochlea is one of the main causes of hearing loss. An artificial basilar membrane (ABM) was developed as a MEMS acoustic sensor using a piezoelectric beam array based on MEMS technology. The lengths and thicknesses of the beams were calculated and determined prior to the design of the photomasks. An aluminum nitride (AlN) thin film was selected as the active piezoelectric layer for the ABM. The impedance magnitudes and phase angles of each beam are measured with an impedance analyzer and a probe station in air. The fabricated ABM contains 16 beams with various lengths ranging from 300 μm to 3300 μm along a trapezoidal shape in the array. The width of the beams is fixed at 200 μm and the thickness of the active AlN thin film is 500 nm. It is observed that the resonance frequencies tend to decreased from 233.3 kHz to 214.6 kHz as the beam length was increased. It is concluded that the fabricated AlN ABM can potentially be used as an acoustic sensor in a total implantable artificial cochlea.