I would never think that ultrasonic wave can do such things. But it’s cool nonetheless.
An excerpt from Engadget:
Ultrasonic levitation has been possible for awhile, but it’s not very practical when objects must typically hover along a single axis. University of Tokyo researchers Yoichi Ochiai, Takayuki Hoshi and Jun Rekimoto have cleared this hurdle with an ultrasonic array that can push items around in 3D space. The machine creates a focal point from a three-dimensional standing wave; users just have to alter the wave’s properties to move whatever is caught inside that point. The technique can manipulate a wide range of materials, and it’s safe to disrupt with your hands. While the array will need to scale up before it lifts objects much larger than matchsticks or screws, it already shows that we don’t need exotic technologies like tractor beams to float things through the air.
Have a look at the video and see how it is done. Amazing!