Subminiature Underwater Propeller with Electrical Controllability of Steering

This paper describes a subminiature underwater ultrasonic propeller with electrically controllability over its propulsion direction. Built on a 200-micron thick nickel-coated lead zirconate titanate (PZT) substrate, the propeller consists of 28 sectors of individually accessible Fresnel lens that are composed of Parylene air-cavity-reflectors on top of the frontside nickel electrode. A backside Fresnel air-reflector is added to prevent any propulsion from the backside that may cancel the propulsion from the front side. The fabricated propeller (4 × 4 mm
²
in size and 37.5 mg in weight) is demonstrated to have control over its advancing direction when assembled on an air-filled capsule.