Hosted by Itai Cohen

Working with Defects

Mechanical metamaterials obtain their unusual behaviour from the collective action of carefully assembled unit cells. While defects adversely affect desired behaviour, here we explore two metamaterials in which the rich physics of defects is harnessed as a design tool instead.

First, snap-through defects can be used to switch a structure between various stable shapes. We study soft sheets with parallel grooves: each groove snaps through to a curved state with a local defect. Collective groove snapping produces a wide array of organic, disorganized shapes that involve rolling and helixing sheet sections. We explore how defects interact with their environment and each other to organize into long chains, and use experiments and minimal models to explore the various shapes these groovy sheets take on [1].

Finally, defects don’t just influence a metamaterial's shape- they also affect its mechanical properties. We discuss architectural defects in planar network-like structures built out of repeating unit cells. It turns out that defects in these structures have a topological charge, that can be felt at the material's boundary. These topological defects act as symmetry-breaking traffic controllers: they steer stresses around their left or right sides [2,3].

[1] Meeussen, A.S. & Van Hecke, M.L. Manuscript in preparation.

[2] Meeussen, A.S., Oğuz, E.C.O., Shokef, Y. & van Hecke, M.L., Topological defects produce exotic mechanics in complex metamaterials. arXiv e-prints, arXiv:1903.07919 (2019). Manuscript in submission.

[3] Meeussen, A.S., Oğuz, E.C.O., van Hecke, M.L & Shokef, Y., Response evolution of mechanical metamaterials under architectural transformations. arXiv e-prints ,  arXiv:1909.11389 (2019). Manuscript in submission.