So far only in computer simulations.  Still this is pretty cool.

One of the key nuts to crack with nanotechnology is how do you make a little motor to power these things.  You can't just shrink a motor down to nano size and have it work.  This solution builds off of several things. 

Electron Tunneling

1. Some bacteria's use of biomotors believed to be powered by proton tunneling.
2. Carbon nanotube technology to build the motor.
3. Electron tunneling

If they can build such a motor then nano-machines become much more viable.  Connecting the power supply to the motors becomes the next trick.

Main article: http://nanotechweb.org/cws/article/tech/36611