A 3D shape with all straight edges and flat faces is a polyhedron. Other 3D shapes with least one curved surface are not polyhedra. A 3D shape with regular polygonal faces, meeting at equal angles, is ...

Old idea reborn: A triangular zipper concept from 1985 has been realised by MIT using 3D printing, decades after manufacturing limits stalled it. Shape-shifting uses: The Y-Zipper can transform floppy ...