Nanotechnology, son… Hmm, never thought about that. But you can think it as being similar to a kagune in Tokyo Ghoul. Think of the hardening happening due to different forces, like it instantly hardens the moment it makes contact with something, sending vibrations throughout the material signaling the hardening, or heat and pressure can trigger it. For the way it shapes into weapons, there are inputs linked to Kaiser’s movement within the cloak, it is a cloak after all, but this isn’t a good explanation so just think that since Ruby is a genius in engineering and because of that, the cloak can just magically form into weapons. And for fighting in it? Not sure what you mean by this, they just fight.