Optimized Encapsulation Design for Reducing Low-Frequency Loss in MEMS Ciliary Hydrophones

To mitigate the low-frequency loss caused by oil-filled encapsulation in MEMS ciliary hydrophones, this study proposes a novel MEMS vector hydrophone cap design. The design incorporates a stainless-steel mesh cap (SSMC) structure combined with polystyrene thin-film deposition technology, effectively focusing sound. Simulation analyses were conducted to determine the optimal dimensions for the hydrophone cap. Experimental results show that the combination of the hydrophone cap and parylene film achieves an 18-dB sensitivity improvement in the low-frequency range (2080 Hz) compared to oil-filled encapsulation, with an operational bandwidth of 20630 Hz.