If you think about it, nanomachines shouldn't be smaller than a bacterium. Just because something isn't below 1 micron it could be qualified as nanotecnology, especially stuff that moves around in a living body. Microtechnology is already used for a different thing. So what, 30k nanometers is still small enough to work safely in blood vessels. Probably it can become smaller by a factor, but i doubt "nanomachines" can or should become smaller than that.