Session: 01-03-01: General topics in vibrations and acoustics

Paper Number: 173975

Two-Dimensional Motion Control of Miniature Robotic Swimmer via Vortex-Induced Propulsion 

Acoustic propulsion presents a compelling alternative to conventional robotic actuation by offering contactless, compact, and mechanically simple means of motion. Unlike traditional systems that rely on motors, linkages, or chemical actuation, acoustic propulsion uses sound waves to generate forces that can be used to steer miniature robotic structures. In this work, we introduce a novel miniature robotic swimmer capable of performing precise two-dimensional navigation, powered solely by acoustically induced forces. The propulsion mechanism is enabled by a custom-designed, 3D-printed Focused Acoustic Vortex Propulsion (FAVP) lens, which converts incident sound energy into spatially focused vortex fields. These fields produce asymmetric acoustic streaming patterns in the surrounding fluid, leading to the generation of controlled thrust that helps propel the swimmer. The FAVP lens features a spiral phase profile that shapes the incoming acoustic wavefront into a helical pattern, producing a vortex beam with orbital angular momentum. When operated under the water surface, this structured acoustic field creates localized fluid motion that interacts with the swimmer's body to induce directional forces. By engineering the phase distribution on the lens and carefully placing the lenses in a specific location under the swimmer hull, the acoustic vortex field can be strategically controlled to generate both linear and rotational motion. This enables the swimmer to execute complex trajectories such as straight-line translation,  rotation, and circular orbiting paths. All of these motions are achieved without any mechanical moving parts or onboard energy storage, highlighting the simplicity and effectiveness of the proposed propulsion system. To validate the concept, numerical simulations to model the acoustic pressure field, vortex formation, and resulting acoustic streaming patterns were performed. These simulations were used to predict the swimmer's motion under different operating transducer voltages and field configurations. Experimental tests were conducted in a water tank using an underwater acoustic vortex system, where the robotic swimmer’s movement was visually observed and recorded to verify the predicted behavior. The experimental results confirmed that the swimmer could be reliably actuated and steered using only the acoustically generated flow fields, with good agreement between predicted and observed motion. This work demonstrates a compact and fully passive robotic platform that harnesses focused acoustic vortex beams for propulsion and steering. The system is highly scalable, cost-effective, and adaptable to various operating environments. Its non-contact and mechanically simple nature makes it particularly well-suited for applications such as microrobotics and autonomous operation in confined or delicate underwater environments. This approach opens new avenues for the design of soft, wireless, and miniaturized robotic systems driven by acoustic energy.

Presenting Author: Chadi Ellouzi Rowan University

Presenting Author Biography: Chadi Ellouzi is currently a Ph.D. candidate in Mechanical Engineering at Rowan University in New Jersey. He conducts his research in the Functional Materials and Structures Laboratory, where he focuses on two main areas. The first involves acoustic metamaterials and metasurfaces, with an emphasis on their applications in the manipulation and control of acoustic and surface waves. The second area centers on acoustofluidics, particularly the use of bulk and surface acoustic waves for the precise manipulation of cells and microparticles. His work bridges fundamental research and practical innovation, contributing to advancements in wave-based technologies and microscale biomedical applications.

Authors:

Chadi Ellouzi Rowan University
Ali Zabihi Rowan University
Farhood Aghdasi Rowan University
Chen Shen Rowan University