We investigate the concentration process of dilute colloidal suspensions up to dense states in a confined geometry: the "microevaporator". This tool is a microfluidic format of a continuous pervaporation experiment. This confined geometry allows the use of simple models, and the analysis of drying of mixtures permits, a priori, to access to both kinetic and thermodynamic informations (activity & mutual diffusivity).
We studied the drying of different "soft matter" systems in this geometry: (i) monodisperse “large” colloids (sulfate latex, 500nm), and (ii) charged dispersions of silica nanoparticles NPs (Ludox, 26nm). We will detail in each case some features of the drying process. Namely, we will show using the first system, that we can form colloidal crystals or amorphous states using the microevaporation technique. We will also show using microfocused SAXS experiments performed at ESRF, that the concentration of the charged NPs dispersion also leads to dense organized colloidal states. Finally, we will point out the crucial role played by the electrostatic interactions on the concentration process.
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