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You may know of Claytronics (aka programmable matter) - the use of reconfigurable nanoscale robots to form shapeshifting objects.
Researchers at Carnegie Mellon University have proposed several basic robotic designs as possible foundations for claytronics, including:

• Planar catoms test the concept of motion without moving parts and the design of force effectors that create cooperative motion within ensembles of modular robots.
  
• Electrostatic latches model a new system of binding and releasing the connection between modular robots, a connection that creates motion and transfers power and data while employing a small factor of a powerful force.
  
• Stochastic Catoms integrate random motion with global objectives communicated in simple computer language to form predetermined patterns, using a natural force to actuate a simple device, one that cooperates with other small helium catoms to fulfill a set of unique instructions.
  
• Giant Helium Catoms provide a larger-than-life, lighter-than-air platform to explore the relation of forces when electrostatics has a greater effect than gravity on a robotic device, an effect simulated with a modular robot designed for self-construction of macro-scale structures.
  
• Cubes employ electrostatic latches to demonstrate the functionality of a device that could be used in a system of lattice-style self-assembly at both the macro and nano-scale.

Videos and detailed info @ Carnegie Mellon - Link

Shape-shifting robot forms from magnetic swarm @ New Scientist - Link

Related:
Claytronics - Link