Nanomotors. The rods that are part of the nanomachines, are coated, one end with platinum, the other with gold. The metals act as a catalyst and break up either hydrogen peroxide, or rocket fuel (hydrazine). While other nanomachines use the metals, it is the way they break up the rocket fuel that gives the kick.
They draw water from the chemicals, and use it as a 'jet' . Of course they use much less rocket fuel than a launch.