Reconfigurable underwater robots with dual-jet piezoelectric synthetic jet thrusters

As underwater exploration advances toward deep-sea operations in complex, unstructured environments, there is a growing need for compact, pressure-resistant robotic systems with enhanced agility and multifunctionality. Conventional electric motor-driven underwater robots struggle to meet these demands due to limitations in dynamic sealing and pressure-resistance. While robots based on functional materials offer miniaturization, they often lack adaptability to complex tasks. This paper presents a compact piezoelectric jet module (3 × 3 × 1.5 cm) with a pressure resistance of 20 MPa, delivering a maximum thrust of 16.4 mN and an average speed of 9.38 cm/s. By employing a dense piezoelectric actuator and an internal-external interconnected structure, the module overcomes the traditional trade-off between depth tolerance and miniaturization. A new explanation for thrust generation in piezoelectric synthetic jet thrusters is proposed based on flow field observations. Two modular reconfigurable underwater robots—Driller and Catcher—are developed using this module and successfully perform tasks in simulated environments. This work contributes to the understanding of piezoelectric jet propulsion and offers a foundation for designing next-generation small, reconfigurable underwater robots.