Metasurface Patterning Turns Ultrasonic Emitters Into Contact-Free "Tractor Beam" Manipulators
By turning objects into "metasurfaces," this contact-free system can not only push them away but pull them again too.
Researchers from the University of Minnesota have developed a new and more efficient way to move objects without physically touching them — using an ultrasonic emitter and metamaterial approach that, they claim, could scale to allow for its use in manufacturing and other robotics ventures.
"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,'" explains Ognjen Ilic, senior author of the study and a professor 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."
Likened to the tractor beam technology found in beloved sci-fi franchise Star Trek, the team's contactless manipulation system allows for bidirectional movement — not only pushing objects away from the emitter but being able to reverse and pull them bag towards the emitter too. The trick: sub-wavelength patterns etched into the surface of the object, which alter its interactions with the ultrasonic soundwaves coming from the emitter.
"Contactless manipulation is a hot area of research in optics and electromagnetism, but this research proposes another method for contactless actuation that offers advantages that other methods may not have," says first author Matthew Stein. "Also, outside of the applications that this research enables, expanding upon our knowledge of physics is just a very exciting thing to do in general!"
"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," adds Ilic. "Often this is done through physical tethers or having to carry some source of energy to be able to perform a task. 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. This gives us a new mechanism to contactlessly actuate things."
The team's work has been published under open-access terms in the journal Nature Communications.