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

Periodic Reporting for period 1 - METAFOAM (Novel assembly strategies in liquid dispersion via interface control – towards cellular metamaterials)

Reporting period: 2019-05-01 to 2020-10-31

The characteristic spatial organisation of structural units in engineered metamaterials accounts for their astounding properties that cannot be found in naturally occurring materials. Smart bottom-up design strategies are key to successful large-scale metamaterial production. However, there are currently no systematic design approaches for mechanically-driven systems with large units. The EU-funded METAFOAM project is addressing the scientific challenges related to interface-controlled bottom-up structuring of bubble packings in initially liquid foam templates which will be solidified. The impact of the research will be twofold: first, it will advance our understanding of the non-thermal packing of very soft objects with tuneable interactions, linking the physics of granular media and biological tissues; second, it will provide new cellular systems for the fabrication and investigation of mechanical and acoustic metamaterials.
The METAFOAM project has been running for 18 months, bringing together physicists, physical chemists, chemists and engineers to advance on our understanding of a-thermal packings of soft object whose interactions are controlled by interfacial effects.

The initial phase of the project involved the setting up of the team and of the lab. Most of the experiments are starting to run, providing first promissing results. Four papers have been published, others are in preparation.

At this stage of the project the team is concentrating on developing approaches to characterise and control the interfacial properties of individual bubbles/drops and films, before investigating how these can be used to control bubble/drop interactions and hence their mechanical self-assembly. The team is heavily involved in developing tools which allow to charactise the evolution of interfaces and foams/emulsions undergoing a transition from a liquid to a solid state, since goal of the project is to use liquid templates for the generation of solid macroporous polymers.
"We have developed a microfluidic ""Thin Film Pressure Balance"" which allows to characterise compex and solidifying thin films, simulating in a controlled manner what happens in foams/emulsions during solidification (Andrieux et al. Lab Chip, 2020)

We could show that the theoritical model developed by S. Millner describes more reliably the sintering process of visco-elastic spheres than traditionally used models. This provides a better control over templating methods for macroporous solids with controlled structure/property relations (Lutzweiler et al. Soft Matter, 2020)."