In the credits, it's just supposed to be some "hi-tech" looking version of that kids game "cat's cradle." I think the only reason it found its way into an episode is that people saw the credits and was wondering, "What the hell does that string have to do with anything?"
It makes its way into a few more episodes after the underground slave ep, too. It's usually always Akira who uses it (in one episode where he enters a fighting tournament rigged by Tube, he tosses it around his opponent to tie them up, after in which it turns into chains).
I don't think the "lazer cat's cradle" was given an official name in Maskman, as it wasn't that important. So I'll just call it "Aura Cat's Cradle." :laugh: