Micro 3D Printer

While researching different 3D printers I found they all use stepper motors for positional control. It got me thinking what other technologies exist that could be used as replacements to improve cost, accuracy, etc. In my industry we use interferometers for nanometer-scale positioning. I wonder how this could be applied to 3D printing. I doubt it will be as cost effective as stepper motors, but it certainly will improve accuracy. Then I got wondering how small you could make a 3D printer. I haven't seen anyone compete for printing the smallest object yet. Well, if you count a FIB as a 3D printer then this doesn't really matter, but I'm still thinking objects observable with the human eye. It might be a fun way to show what the technology is capable of doing and possibly open up some new markets or applications. So for positioning control you could use simple, amateur interferometers. Maybe modify the kind used for amateur astronomy. There are other positioning technologies that might be better suited. This may also require a change in the actuators for improved accuracy.