➀ The study introduces a capillary effect-based sealing strategy to address air leakage and asynchronous vibration issues in piezoelectric MEMS speakers. ➁ This method uses PDMS liquid to autonomously seal the narrow gaps in the speaker structure, improving low-frequency and resonant frequency sound pressure levels. ➂ The sealed speakers showed a 4.9 dB increase in sound pressure level at 20 Hz and a 17.5 dB improvement around the resonant frequency, with minimal impact on other frequency performance.