METAFOAM · Novel assembly strategies in liquid dispersion via interface control – towards cellular metamaterials

The astounding properties of metamaterials result from a characteristic spatial organisation of purpose-designed structural units. Research on metamaterials has greatly advanced thanks to their reliable top-down fabrication (lithography, 3D-printing,...). For large-scale production, however, smart bottom-up design strategies are required, for example through self-assembly of the structural units. While this has been developed for thermally-driven systems with sub-micrometric units, no systematic design strategies are established for mechanically-driven systems with larger units. The METAFOAM project will fill this gap by addressing the scientific challenges towards controlled bottom-up structuring of bubble/drop packings in liquid foam/emulsion templates. While “ordinary” foams/emulsions have been investigated in depth, the control over their structure is very limited. The METAFOAM project will provide access to very different structures by explicitly tuning the bubble/drop interactions through the presence of a polymeric skin with controlled repulsive, adhesive and frictional properties. We will develop methods to reliably create/characterise these skins and establish a state diagram which systematically relates the resulting bubble/drop interactions and the foam/emulsion structure. Solidification of the most promising structures will provide new types of cellular polymers with currently inaccessible mechanical or acoustic meta-properties: high stiffness-to-weight-ratios, negative Poisson ratios, and acoustic band-gap properties.The impact of this interdisciplinary project at the interface between physics and chemistry is therefore two-fold. In the liquid state it will advance our understanding of the a-thermal packing of very soft objects with tuneable interactions, linking the physics of granular media and biological tissues. In the solid state it will provide new cellular systems for the fabrication and investigation of mechanical and acoustic metamaterials.