Dr. Chiel talked to me a bit about materials that can stiffen and soften on command. He envisioned a sort of clasp that when stiffened would secure a shoe, and when softened would loosen it enough to be removed. That kind of thing could be achieved with a variety of materials, including shape-memory alloy wires like nitinol. Nitinol is a metal that is molded into a specific shape (like, say, a spring) while hot. When cooled, it can be stretched into any position, but if you send an electrical current through it, it'll "remember" its shape and return to it. At the moment, that kind of alloy requires quite a bit of electrical current, which heats up and might be unappealing as footwear, but in principle, you might not need that much power simply to trigger the material to move in one direction. Imagine a hanging chandelier: you'd need a lot of energy to hold it up, but if it's hung from the ceiling, the only energy it requires is enough to actually move it.