A Multi-Stress Concentrated Butterfly Electrode MEMS Acoustic Sensor with High Sensitivity in Infrasound

Infrasonic underwater sensing remains a critical challenge due to the limitations of conventional acoustic sensors in achieving high sensitivity at very low frequencies. This paper presents a piezoelectric MEMS acoustic sensor featuring a multi-stress concentrated butterfly electrode (MCBE) design. The multi-stress concentration mechanism is achieved through the integration of semi-annular slots, short narrow islands, and a cross-beam structure, while the butterfly electrode facilitates differential input, collectively enhancing the sensor's sensitivity. Without amplification circuit, the MCBE sensor achieves a sensitivity exceeding −170 dB below 10 Hz, with a peak value of −154.71 dB@5 Hz (referenced to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1 \text{Vrms }/\mu \text{Pa}$</tex>). The MCBE sensor's maximum nonlinearity is only 0.41%, which substantially broadening the dynamic detection range. These outstanding performances of the MCBE sensor highlight its remarkable potential for infrasonic underwater applications.