Mechanical Metamaterials

Auxetics for geometry control

Auxetic materials expand in all directions when a tensile force is applied in one direction. Because of this negative Poisson's ratio effect, there are various expected geometrical properties which are synclastic curvature in bending and variable permeability hardly observed in natural, non-auxetic materials. When out-of-plane bending is applied to auxetic materials, the surface displays the dome-like shape with a synclastic curvature. And porous auxetic materials improves permeability by adjusting the size of its pores as each unit cell unfolds in all directions. Also, if rotating rigid units with triangular patterns are inserted into these flat materials, the material gets much more freedom and can approximate a non-developable surface. Here, by using these kinematical characteristics, we are trying to design and control various kinds of shapes. This design process offers ample opportunities to construct material aware surface.