So, I have this draft for a story. It's basically a parody(?) of the fantasy tropes originating from LOTR (the movies) with the twist that we're following the bad guy's lackeys, who he abuses more than his enemies.
In one scene, the lackeys get surrounded by the bad/good guys with no chance of escape. That's when their section commander decides to use his ultimate technique, to give his underlings a chance to escape. This ability is called:
Utility-fog Whirlwind. It takes the work of a lot of foglets (the tiny robots that together make up the fog) to create and maintain this barrier but, whilst active, it can block off a large (10-meter radius) area around a given point by surrounding it with a wall of several localized wind vortexes that are able to hinder movement and blow away lighter objects (not humans, though).
The maximum length of the wall is 62 meters.
For now, let's not consider the problem of energy. How could the robots accelerate either themselves, or the air, or both, to create a strong enough wind vortex that normal humans can't pass and could last for a while?
Though it's called whirlwind, and I'm talking about vortexes, if there's a more efficient solution, feel free to change that part. Also, it's pivotal that it's possible to shape the wall (I.e: change its curvature).