From DARPA's proposal at: http://www.darpa.mil/baa/baa07-21mod2.html
"...the Defense Advanced Research Projects Agency (DARPA) is seeking innovative proposals to develop Chemical Robots (ChemBots): soft, flexible, mobile objects that can identify and maneuver through openings smaller than their static structural dimensions; reconstitute size, shape, and functionality after traversal; carry meaningful payloads; and perform tasks. ChemBots represent the convergence of soft materials chemistry and robotics to create a fundamentally new class of soft meso-scale robots that can perform the following key unit operations in sequence:
1. Travel a distance;
2. Traverse an arbitrary-shaped opening much smaller than the largest characteristic dimension of the ChemBot;
3. Reconstitute size, shape, and functionality after traversing the opening;
4. Travel a distance; and
5. Perform a function using the embedded payload."
Liquid robots, here we come.