How they manufacture them ?
Well let´s see whether my english is good enough for this.
The basic technique is in theory simple: You have a "stable" layer on which you deposite a sacrificial layer and then you deposite another stable layer. Since you will have openings in the last layer you can etch the sacrificial layer away and you have a hovering layer.
If you do this more than once and stack the residual parts correct you can do gears or a dlp.