I'm sure that the people working on making tinier & tinier robots are motivated by doing great things, but I think they're missing an obvious win.
Make #TinyBots or #NanoBots that work in cooperation to make the perfect haircut, chosen from a screen.
A tube/conveyor above & below head.
A stream of nanobots drop onto head from top tube. Each bot crawls across scalp to the next bundle of 10 or so un-cut hairs, climbs the correct distance, cuts them, carries them to the bottom tube.
And braids!