FWF - PARTINTER - Arches and avalanches in particle-laden interfaces

The project „Arches and Avalanches in Particle-Laden Interfaces” focuses on liquid interfaces stabilized by a dense layer of micro-particles which adsorb onto them. This adsorption and the resulting stabilization are driven by capillarity i.e. by the fact that at micro- and millimetric scales the shape of a liquid portion is fixed by the minimization of its surface energy. While largely unknown from most of us, these interfaces are common both in nature - in the form for example of rain drops covered by pollen, dust or sand - and in industrial products such as emulsions and ultra-stable foams… Yet, to date, the relation between the macroscopic properties of these interfaces and the attributes of the individual particles which constitute them remains poorly understood. The lack of knowledge is especially problematic for large and fast deformations which indeed correspond to the typical conditions encountered during industrial processes. The present project aims to fill this gap following an original experimental approach. The latter is based on two aspects: the careful engineering of particles showing different and controlled properties and the observation of the interfacial compression/decompression at the micro, meso and macro levels simultaneously. To do so an interferometer will track the position of individual particles with respect to the liquid interface, high speed imaging will record the changes in particle packing and density at the level of tens to hundreds of particles while changes of shape and pressure will be measured at the interface level. The results will be used to improve existing models which mainly fail because they rely on a continuous approach considering the interfaces as elastic membranes. Our data should enable us to account for their granular character and therefore render unexplained phenomena such as arches and avalanches.