Design, Fabrication, and Application of Mechanical Metamaterials Using Point Group Symmetries

Thesis (Ph.D.)--University of Washington, 2022With the advance of manufacturing, metamaterials have seen a new wave of interest in recent years. Applications range from robotics and energy absorption to architecture, medical devices, and mechanisms. But we are still in the early stages of metamaterial research. Many studies have focused on the invention and characterization of a material or small group of materials that can be manufactured using additive manufacturing processes. Fewer have discussed design tools. The work here presents the development of point group metamaterials, fabrication, and applications thereof. I demonstrate the power of using group theory and kinematics for designing metamaterials. Group theory, in the form of the point, line, and space group symmetries, defines all of the ways in which a discrete unit can be tiled in space, making it a powerful tool for designing cellular materials and repeating structures. Applying this to kinematics, the geometric design of rigid body linkages, allows us to construct moving metamaterials by exploring the evolution of states of a small unit cell that tiles to form a material. In combination we can build structures with links that both rotate and bend on an evolving surface. In this work I have demonstrated the utility of axial point group symmetries for constructing a range of 3D auxetics with new material properties such as locking, switching, and joint behavior. I show how these cells can be tiled in space to build metamaterials. Then I apply these designs to build a compliant actuator and construct a novel soft robot manipulator capable of performing assembly and inspection tasks