Cool stuff! I'm curious what limitations there are on how fast the particle can move. Is it theoretically possible to move a single particle fast enough to render complex shapes in real time, or will you need many particles for that?
Thanks for both your answers. Though I was also thinking perhaps you could just suspend the particles in mid-air, and use the movable prism in a laser projector to actually "render" the projection (thus not needing to move them at at a high frame rate or at all). However I guess, you probably do need to move the particles as well to be able to make it a 3D volumetric shape in space (seen from all angles etc).
I'm not very familiar with the plasma dots approach, but from a cursory look it appears that it is not capable of RGB. On the other hand, there is nothing that can fall out of confinement so the display is probably more stable.
That page says the femtosecond plasma display is pretty safe. This display was - and I believe still is, though I could be wrong - using a UV laser for confinement, which is sorta scary.
> Can you levitate multiple particles at the same time?
Yes, but their device currently is only capable of levitating a single particle. With the current approach, the device would need one laser for confining each particle. The lasers used for RGB could potentially be multiplexed between particles, but this is less likely to work for the confinement due to the instability of the trap.
> How fast are they moving?
Pretty slow. All the "big" images (Leia, grad student, etc) are long-exposure. You can see the particle moving in real-time at about 0:50. In the videos, you can see the device can almost do real-time persistence of vision for volumes substantially smaller than a fingertip.
> How sensitive is it to disturbances in the air?
As I mentioned above, the confinement is weak and the trap is pretty unstable. Its possible that they have improved the longevity of the trap in the last few months, but when doing long-exposure the device is surrounded by a heavy cloth barrier to block both external light and air movement.
The cellulose comes from the black liquor on a spoon (see 0:46 in the video). The put the spoon at the focus of the laser and with luck some particles get confined. After the trap is lost, the particle just sort of drifts away in the air, since they are only tens of microns.