This is the stl files associated to a morphable metamaterial. Undeformed, it has flat faces, but when compressed, its texture morphs into a smiley face. In order to work, the metamaterials have to be printed in flexible material.

For more details, see the related videos https://youtu.be/9UfMrOa4wKs?list=PLF7h0c1YQiRaMMhKmDRUpX5ptiFseSEkS https://youtu.be/NxcCtimWxn0?list=PLF7h0c1YQiRaMMhKmDRUpX5ptiFseSEkS

and the scientific paper http://www.nature.com/nature/journal/v535/n7613/full/nature18960.html and preprint https://arxiv.org/pdf/1608.00625.pdf