Utility-fog wind?

Question

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).

Answer 1

In a 10x10x10 meter area you are talking about close to 1 trillion foglets. That many "legos", you can have them create just about any complex object you would like.

For your whirlwind they could form into connected giant fan-blades... because they are foglets, no axles or other structure is required, they begin spinning and could quickly create a directed wind.

If the encounter is in a tunnel, having the fan fill the tunnel wall-to-wall, and spin, they would create a wind-tunnel effect... your lackeys would need to hang on or be sucked through the blades while their adversaries got blown down the tunnel.

The foglets (being 100-micrometers) as a blade edge would be super sharp. They would be a rather deadly blade-barrier as spinning fan blades. There would be some loss of foglets but the amount of damage they could do at speed would be devastating.

Answer 2

I can't imagine any way to accomplish this using any tech whatever. As one of the comments says, getting this kind of energy out of nanites is going to be a tall order.

The problem is to make it thin and strong enough to block a human. But at the same time not destroy what is inside.

Imagine a huge pile of jet engines set in a ring.

https://www.youtube.com/watch?v=DFP4xl0V0mk

Start about 55 seconds into the vid. A jet engine can blow away a utility truck. If you had a ring of them strong enough to interfere with human sized opposition stepping through, the combined ring would be powerful enough to uproot trees for many times the radius of the ring. Whoever is standing inside the ring will not be having a good day.