Researchers have put a new spin on the idea of "hands free" by using ultrasound waves as a way to move objects around, they said. A team from the University of Minnesota Twin Cities has developed a method that can move larger objects than was previously possible using ultrasound by using the principles of metamaterial physics, they said.

Their research paves the way for using new forms of contactless manipulation in industries such as manufacturing and robotics, with devices that won't need built-in power sources to move around, researchers in the university's Department of Mechanical Engineering said.

While researchers have experimented for some time with using waves, light, and sound to manipulate objects, their work uses physics to make the surface of objects a metamaterial surface, or "metasurface," which allows them to manipulate much larger objects than previous techniques, said Ognjen Ilic, a University of Minnesota assistant professor in 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," he said. "And in doing that, we can control the acoustic force that is exerted on an object.”

(Meta)material Matters

Metamaterials are materials that are artificially engineered to interact with light and sound waves, including ultrasound waves, researchers said. Their method depends upon placing a metamaterial pattern on the surface of an object, which allowed the research team to use sound to steer it in a certain direction without physically touching it, they reported.

Researchers used this technique to demonstrate how they can move an object both forward as well as pull it toward a source. This type of manipulation could be applied to moving objects in a manufacturing setting or for creating robotics that can move around autonomously, they said.

Indeed, scientists are keenly interested in the potential for leveraging contactless manipulation in the fields of optics and electromagnetism, noted Matthew Stein, a graduate student in the university's Department of Mechanical Engineering who worked on the research. He said that the method he and his colleagues developed "offers advantages that other methods may not have."

From Concept to Application

Researchers published a paper on their work in the journal Nature Communications.

“In a lot of fields of science and engineering, robotics especially, there is the need to move things, to transfer a signal into some sort of controlled motion,” Ilic said of his team's work. “Often this is done through physical tethers or having to carry some source of energy to be able to perform a task."

While the research is aimed at demonstrating a new concept for contactless manipulation rather than applying it to a specific purpose, he said the research team plans to test it with higher frequencies of waves and different materials and object sizes in the future to continue their exploration.

"I think we’re charting in a new direction here and showing that without physical contact, we can move objects, and that motion can be controlled simply by programming what is on the surface of that object," Ilic said. "This gives us a new mechanism to contactlessly actuate things.”