Shearing Spherical Auxetic Cells and Mechanisms

Technology

This method generates patterns for auxetic spheres, tubes, and capsule structures that feature a hand-twisting expansion element. Such handedness enables flexible systems that self-lock into an expanded state when the system is turned in one direction. When turned in the opposite direction, elements of the system compress to a collapsed state.

Patterns for handed auxetic structures involve a system of links and interconnected unit cells that rely on a certain type of symmetry (22N symmetry in the Conway notation). Additional design elements can impose flexibility along certain axes to allow for multiple auxetic structures to lock into each other. These particular design features result in deployable structures that can be locked into a fully rigid state at a later time.

Problems Addressed

Auxetic materials and structures have a negative Poisson's ratio, which means they counterintuitively expand when stretched laterally. Previous work on auxetics focused on understanding this anomalous behavior. More recent work focuses on exploiting these unique characteristics to enhance existing systems and products. The inventor has developed a method to produce 2D sphere tiling and cylinder patterns for a new class of handed auxetic structures.

Advantages

• Self-locking structures that feature a hand-twisting expansion property
• Scale independent design that promotes a variety of possible manufacturing techniques
• Bi-stable mechanism useful for deployable structures
• Net handedness enables concentric deployment of multiple auxetic spherical shells