A new way to move objects offline

Materials with Metasurface

By placing a pattern of metamaterial on the surface of an object, the University of Minnesota researchers were able to use sound to point it in a specific direction without physically touching it. Credit: Olivia Hultgren

This contactless processing method has potential applications in industries including robotics and manufacturing.

A team of researchers at the University of Minnesota Twin Cities has discovered a way to manipulate objects using ultrasound, paving the way for contactless motion in industries like manufacturing and robotics without the need for an internal power source.

The results have been published in the peer-reviewed journal

While it’s been demonstrated before that light and sound waves can manipulate objects, the objects have always been smaller than the wavelength of sound or light, or on the order of millimeters to nanometers, respectively. The University of Minnesota team has developed a method that can move larger objects using the principles of metamaterial physics. 

Metamaterials are materials that are artificially engineered to interact with waves, like light and sound. By placing a metamaterial pattern on the surface of an object, the researchers were able to use sound to steer it in a certain direction without physically touching it. 

“We have known for a while that waves and light and sound can manipulate objects. What sets our research apart is that we can manipulate and trap much bigger objects if we make their surface a metamaterial surface or a ‘metasurface,’” said Ognjen Ilic, senior author of the study and the Benjamin Mayhugh Assistant Professor in the University of Minnesota Department of Mechanical Engineering. “When we place these tiny patterns on the surface of the objects, we can basically reflect the sound in any direction we want. And in doing that, we can control the acoustic force that is exerted on an object.”

Video of the researchers moving an object with ultrasound. Credit: University of Minnesota

With this technique, researchers can not only move an object forward, but also drag it toward a source — not much different from the tractor-beam technique in science fiction stories like Star Trek.

Their method could be useful for moving objects in fields such as manufacturing or robotics.

said Matthew Stein, first author on the paper and a graduate student at the university from the Minnesota Department of Mechanical Engineering. “Also, outside of the applications that this research enables, expanding our knowledge of physics is a very exciting thing to do in general!”

While this study is more of a show of concept, the researchers aim to test higher wave frequencies and different materials and sizes in the future.

“In a lot of areas of science and engineering, especially robotics, there’s a need to move things around, to convey a signal to some kind of controlled motion,” Elik said. This is often done through physical tethers or having to carry some energy source around to be able to perform a task. I think we’re planning in a new direction here and showing that without physical contact we can move things, and that motion can be controlled simply by programming what’s on the surface of that object. This gives us a new mechanism for stimulating things without contact.”

Reference: “Formation of Contactless Radiation Forces by Anomalous Acoustic Scattering” by Matthew Stein, Sam Keeler, Yuji Lu, and Eugene Elik, November 1, 2022, Available here. Nature Communications.
DOI: 10.1038/s41467-022-34207-7

The study was funded by the Minnesota Robotics Institute and the Air Force Office of Scientific Research.

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