Swiss researchers from the Federal Institute of Technology in Lausanne, collaborating with teams in France, Austria, and Kazakhstan, have demonstrated the ability to steer floating objects with sound waves. The findings were published in the science journal Nature Physics (NatPhys).
In a controlled laboratory setup, the team used ping-pong balls that drifted on a shallow pool. A deliberate arrangement of speakers at opposite ends emitted carefully tuned sound waves that propelled the balls along a predetermined route. A second set of microphones captured the reflected waves, forming a scattering matrix that served as real-time feedback for the system.
By coupling this scattering matrix with precise camera tracking of the ball, the researchers computed, on the fly, the optimal acoustic driving force needed to keep the object on its intended path. This closed-loop approach means the system can adapt instantly to changes and correct deviations as they happen, making the motion highly controllable despite minor disturbances in the environment.
Researchers emphasized that the principle rests on the conservation of momentum, a fundamental rule that allows the method to be surprisingly simple and broadly applicable. This universality is what gives the technique its appeal for practical use in diverse settings, from delicate laboratory experiments to real-world applications where precise motion control is essential.
Beyond simple spheres, the team explored more complex shapes using origami-inspired designs and successfully guided a paper lotus flower along a scripted trajectory. This demonstrated the method’s versatility when the geometry of the moving object deviates from a perfect sphere, broadening potential applications in soft robotics and material handling where irregular bodies are common.
Further tests introduced fixed and moving obstacles to create heterogeneity in the environment. The system performed well enough to steer the object around scattering centers, showing that wave-pulse shaping can operate effectively in dynamic, uncontrolled contexts—an important step toward uses that resemble real biological and industrial scenarios where obstacles and variability are the norms.
Experts see promise in translating this capability to medical contexts, where precise delivery of agents to targeted locations is critical. If refined, the technique could contribute to accurate placement of therapeutic payloads, potentially improving outcomes in treating tumors and other diseases by reducing collateral exposure and enhancing treatment efficacy. The researchers note that such directional control could complement existing methods for targeted delivery, offering a noninvasive means to guide substances to specific regions within complex biological environments. (NatPhys, 2023)
Previous work in related areas has explored targeted release of drugs from nanocapsules using ultrasound, highlighting a broader trend toward using wave-based methods to influence movement and delivery inside the body. The current study extends that concept by showing how acoustic fields can actively steer objects in a controlled fashion, providing a new tool for researchers and clinicians exploring precise, noninvasive control mechanisms. (NatPhys, 2023)