Bastiaan Florijn


 Mechanical Metamaterials


Metamaterials derive their unusual properties from their structure, rather than from their composition. Important examples of mechanical metamaterials are auxetic (negative Poisson's ratio) materials, materials with vanishing shear modulus, materials with negative compressibility, singularly nonlinear materials and topological metamaterials. Of particular recent interest are mechanical metamaterials whose functionality relies on elastic instabilities, such as quasi 2D slabs perforated with a square array of holes. When compressed, these ``holey sheets'' undergo a buckling-like pattern transformation, which can be explored to obtain switchable auxetics, chiral and phononic properties and 3D ``buckley balls''. An important limitation common to all these metamaterials is that each mechanical functionality requires a different structure.[1]


 Holey Sheets


We create mechanical metamaterials whose response to uniaxial compression can be programmed by lateral confinement, allowing monotonic, non-monotonic and hysteretic behavior. These functionalities arise from a broken rotational symmetry which causes highly nonlinear coupling of deformations along the two primary axes of these metamaterials. We introduce a soft mechanism model which captures the programmable mechanics, and outline a general design strategy for confined mechanical metamaterials. Finally, we show how inhomogeneous confinement can be explored to create multi stability and giant hysteresis.[1]





Mechanical metamaterials in the media

'Knijpen voor de wetenschap' - Leids Universitair Weekblad Mare (7 maart 2013)

'Toveren met metamateriaal' - Telegraaf (Za 26 Juli 2014)






[1] Bastiaan Florijn, Corentin Coulais and Martin van Hecke arXive 1407.4273