Something that always amazes FabLab visitors, is flexible wood. By laser cutting special patterns in the wood, it is possible to make the wood flex without breaking. Aaron Porterfield has created an instructable with different patterns to create flexible wood (http://www.instructables.com/id/Curved-laser-bent-wood/). The flexibility of the wood is dependent on the thickness of the wood, the shape of the pattern and the size of the pattern. You can read more about the physics: http://www.deferredprocrastination.co.uk/blog/category/def-proc/lattice-hinges/
Today, I made some flexible Christmas ornaments for the Christmas tree. We will need some general geometry and of course the flexibility patterns. I will cut the ornaments in 3mm MDF. If you want to create flexibility patterns for other materials or another material thickness, you will need to experiment with the pattern dimensions.
To read more about I created the patterns in Inkscape, go to my blog: http://make.petervdb.be/2015/12/23/flexible-christmas-ornaments/