Nanotech, at least intended in sense of extreme miniaturisation, is making progress as scientists understand better and better the structure of matter and learn how to turn this to their advantage by creating "smart" materials that can react to external stimuli.
This is the case of researchers at the Johns Hopkins University that have invented micro grippers that can pick up single cells and even deliver micro doses of drugs to very specific points, e.g. for killing cancer cells.
One of the problems with robotics is that you need power and this is provided by tethering the robot with cords supplying it. An alternative, particularly when working at microlevel is to use materials that can harvest energy and use it. A class of materials that can just do this is hydrogels. They can swell (and hence crete a force) in certain condition, like changes in temperature, acidity, light. The downside is that they are soft and the forces they can create is not effective in most situations.
The researchers at the Johns Hopkins have managed to couple hydrogels with a stiff biodegradable polymer material that can funnel the force generated by the hydrogel and make it effective.
To steer the grippers to the place they are needed the researchers have embedded magnetic nanoparticles so that they can be moved by a magnetic field. These magnetic particles are also important in providing information on where the grippers are at any particular moment.
So just imagine injecting some hundreds of theses grippers into a vein and guiding them to a very specific place where there is a tumour. Once you have the grippers in place you can activate them by using lasers or ultrasound to heat them up, thus providing the energy needed. They would be delivering the drug molecules right where it is needed.
The amazing thing is that this could be the bases for a science fiction book, and instead it is material for a science book!