Russ Angold, the co-founder and CTO at exoskeleton maker Ekso Bionics, says he can tell how old someone is by which pop-culture reference they make when he tells them what he does for a living. Kids talk about the suit Tom Cruise wears in Edge of Tomorrow. Millenials name-check Iron Man. Gen-Xers go classic: Sigourney Weaver in Aliens. Nobody ever mentions Starship Troopers. But building a power-enhancing exosuit isn’t easy. And nobody knows that better than Ekso.