“May The Force Be With You!”

Researchers at the University of Minnesota have developed a way to freely manipulate objects with the help of ultrasound waves.

“We’ve known for a long time that waves and light and sound can manipulate objects. What makes our research different is that we can manipulate and trap larger objects if we make their surface a a metamaterial surface, or a ‘meta-surface,'” said Ognjen Ilic, senior author of the study and the Benjamin Mayhugh Assistant Professor in the University of Minnesota Department of Mechanical Engineering.

Scientists have previously shown that light and sound waves can manipulate objects, objects often smaller than the wavelength of sound or light, or in the order of millimeters to nanometers, respectively. The team at the University of Minnesota has developed a method that can move large objects using the principles of metamaterial physics.

Metamaterials are artificially designed materials that can interact with waves such as light and sound. By placing a metamaterial pattern on top of an object, researchers were able to use sound to guide it in a direction without physically touching it.

“If we put these little patterns on the surface of things, we can reflect the sound in any direction we want. And by doing that, we can control the acoustic force applied to an object. Using this technique, researchers can not only move an object forward but also pull it toward a source—not too dissimilar to the “force” depicted in Star Wars.

“Contactless actuation is a hot research area in optics and electromagnetism, but this research suggests another method for contactless actuation that offers advantages that other methods cannot,” said Matthew Stein, first author of the paper and a graduate student in the University of Minnesota Department of Mechanical Engineering. “Also, aside from the applications this research can make, expanding our knowledge of physics is just an exciting thing to do in general.” Researchers intend to test higher frequency waves and different materials and object sizes in the future.

Reference: Matthew Stein et al, Shaping of contactless radiation forces by anomalous acoustic scattering, Communication in Nature (2022). DOI: 10.1038/s41467-022-34207-7