4D Printing

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I have a 3D printing community and I know there is a level above that: 4D printing. Taking three dimensional shapes and making those shapes transform over time when triggered.

I've tried to find some examples of projects that can be done by normal DIYers in their garage or hobby room but I can't seem to find many. Most sources that discuss 4D printing such as all3dp.com refer to "special materials" like shape-memory alloy. Although accessible to an extent, those kinds of materials aren't quite common.

The closest examples I can find to a DIY 4D printed project using common materials easily accessible for DIYers is an instructables.com collapsible lantern and an expanding wrist watch shield. The latter is closer to what I had in mind when trying to find 4D printing projects.

Any engineers out there working on their own 4D printing projects or have any interesting ideas for projects?