The soft glassy material rheology is highly peculiar in many respects. To begin with, it shows a non-linear relation between the applied stress and the resulting strain, often exhibiting yield stress, i.e. no flow below a given applied stress threshold. Yield stress plays a central role in controlling the occurrence of plastic events, i.e. topological rearrangements of the density configurations, which shape up the kinetic pathway of the soft materials towards their thermo-mechanical equilibrium through the release of stress and decrease of the interfacial area.
The interface dynamics is controlled by the competition/cooperation of several concurrent interactions; pressure, long-range hydrodynamics, near-contact capillary forces and viscous dissipation. At low surface/volume ratios (low volume fraction of the dispersed phase, say oil in water for the case of emulsions) this competition can be treated by suitable multiphase/component extensions of the Navier-Stokes equations of continuum mechanics. At high surface/volume ratios (low surface tension) however, different portions of the interface come in near-contact, thereby triggering the effects of the short-scale capillary and dispersion forces, such as disjoining pressure.
This is precisely the fundamental framework which COPMAT inscribes to. Interfacial complexity is significantly accrued once the effects of confining walls are taken into account.
How does the interface interact with solid walls? How does such interaction depend on the wettability properties of the flowing materials? How does it change in the presence of unwanted or engineered nano-corrugations? These are some of the fundamental questions which bear a key impact on the microfluidic design of new porous materials.
These crucial questions are investigated in full depth, by means of a new class of full-scale simulations, nano and macroscales (nm to mm), over a broad range of process parameters, such as liquid volume fraction, poly-dispersity of the initial conditions, size of the confining microfluidic devices.
