Feasibility validation of piezoelectric actuators under full-ocean-depth pressure conditions: A study based on M-shaped hybrid-mode design

Due to the extremely high pressures in the deep sea, traditional rigid actuators typically require protective vessels and pressure-compensation systems, leading to complex structures and increased risk of structural failure. The inherent adaptability of piezoelectric excitation and friction-coupling drive to high-pressure environments suggests that, theoretically, piezoelectric actuators can operate in full-ocean-depth pressure conditions with an open, direct-immersion structure without requiring bulky pressure-compensation systems. However, the feasibility of piezoelectric actuators operating in full-ocean-depth pressure environments (0-110 MPa) remains unvalidated. To address this, we designed an M-shaped hybrid-mode piezoelectric actuator to experimentally verify its performance under full-ocean-depth pressure conditions. The actuator's structural dimensions were determined using the finite element method to meet the requirements of frequency degeneracy. We developed a high-pressure water simulation system and measured velocity to evaluate the actuator's performance in simulated full-ocean-depth pressure environments. Our results demonstrate that the actuator prototype operates successfully under pressures up to 110 MPa, equivalent to a depth of 11 000 m, the Earth's deepest point. In addition, the actuator's velocity remains stable across hydrostatic pressures ranging from 0 to 110 MPa. Although our experiments focus on the M-shaped hybrid-mode design, this actuator embodies the core principles of piezoelectric excitation and friction-coupling drive, which are broadly applicable to various piezoelectric actuators. By validating this design, we broaden both the structural configurations and driving mechanisms available for piezoelectric actuators and provide key insights into the feasibility of piezoelectric actuators operating under full-ocean-depth pressure conditions.