I welcome our nanotech termite robot grey goo overlords
One step closer to the science-fiction implementation of nanotechnology: self-replicating robots small enough to manipulate individual cells in the body, or in the extreme example, atoms of matter. It could be the ultimate expression of technology, which is all about controlling the environment surrounding us; in theory, there is very little molecular nanotech could not build, or destroy, with astonishing speed.
The more plausible cellular nanotechnology, which I have reasonable hopes of seeing in some early stage by the end of my life, would be a tremendous benefit to dealing with organ failure, wound regeneration, and maybe even cancer. How does non-invasive major surgery grab you? Just inject nanobots programmed to perform the procedure into a damaged organ, let them do their thing, and then the body naturally flushes or assimilates them as waste.
To get there, several developments are required. The ability to build teeny tiny robots is probably the least of the technological hurdles. Programming them was a bigger step, and your story sounds like a great step in that direction. This "decoupling of complex problems" will be vital for making the nanotech concept work.
Then you've got the need for energy, which is also the currently postulated limiting factor for the dreaded "grey goo" scenario, in which rogue nanotechnology kills us all - in fact, it was feared by early theorists that it might get out of hand (or be deliberately weaponized) into an endlessly spreading virus that essentially digests all organic matter on Earth, leaving a barren rock covered with formless grey soup. Whoops!
There's been a lot of interesting theoretical debate on whether the grey goo scenario was possible over the past few years. The scientist who coined the phrase later said he regretted bringing it up and freaking so many people out. The big objection raised by the new generation of theorists is that rogue nanotech would not have enough energy to spread as more than an extremely localized threat; basically, it runs out of gas by digesting everything useful for energy around it, then goes inert. The nanotech might be able - either through deliberate design or automated evolution - to consume itself for emergency power, but eventually that little game runs out too, and the spread of the grey goo inevitably halts.
Unless, of course, our quest for sustainable energy produces something like hyper-efficient solar power on a micro-scale - some nanites in your body migrate to your epidermis, soak up sunlight, and relay the energy to the rest of the little buggers so they can work the night shift. Or maybe we'll come up with a form of micro-fusion, or they could run off the Earth's magnetic field...
Solar-powered killer robot termites for the win!