These are examples of structures designed by optimization methods. The three-dimensional model is a super-stable tensegrity composed of tension and compression components.
American architect Richard Buckminster Fuller defined it as an “island of compression in a sea of tension”. The two-dimensional model is a periodic structure with a negative Poisson’s ratio. Unlike conventional materials, when the structure is stretched in one direction, it expands in the perpendicular direction.
Large discrete structures with such special physical properties can now be designed by optimization methods (especially based on mixed integer programming).

A super-stable tensegrity
Courtesy: Mathematical Informatics 5th Lab, Department of Mathematical Engineering and Information Physics, Faculty of Engineering, The University of Tokyo
Collection: Department of Mathematical Informatics, Graduate School of Information Science and Technology, The University of Tokyo

A periodic structure with negative Poisson's ratio
Courtesy: Mathematical Informatics 5th Lab, Department of Mathematical Engineering and Information Physics, Faculty of Engineering, The University of Tokyo
Collection: Prof. Yoshihiro Kanno, Department of Mathematical Informatics, Graduate School of Information Science and Technology, The University of Tokyo
Structures designed by optimization methods: a tensegrity and a periodic structure with negative Poisson's ratio