This video describes a volumetric display I designed and built that uses a phased arrray of ultrasonic transducers to levitate a 1mm foam ball and move it at speeds greater than 1m/s. The POV effect makes it seem as if you're drawing in mid-air!
This was such a fun project - I still giggle (maniacally) when watching this thing go. There's something truly magical about watching something levitate in mid-air and then start zipping around so fast, you can't see it.
You can find all the design files here: https://github.com/danfoisy/vdatp
References:
PhysicsGirl acoustic levitator:
https://www.youtube.com/watch?v=ABjRnSYw-4k
Acoustic levitator Instructable:
https://www.instructables.com/Acoustic-Levitator/
University of Sussex video:
https://www.youtube.com/watch?v=Tm8JRlJ1q50
University of Sussex paper:
http://sro.sussex.ac.uk/id/eprint/86930/