Interesting but the brief doesn't explain what 4-D printing is, which sort of reduces whatever technique they used to a cheap buzzword.

If I was less lazy I'd read the cites and report back, but alas, sloth.

Edit: OK, I've done it. It's just 3D printing objects that change shape over time once they're printed, 3D-ly. I really like that people are thinking about how to achieve this environmentally mediated shape changes but the marketing buzzwords suuuuuuuuck