Characterizing Phase Separation in Colloid-Polymer Dispersions through Solvent Extraction in Microfluidic Droplet Arrays

Nanoliter droplets formed using microfluidic techniques have proven useful as components in tunable emulsions and as uniform microreactors. When observed for extended periods, there is significant transport of solvent from the droplet phases to the continuous fluid and material of the microfluidic device. This transport is utilized to control to composition of multicomponent colloidal dispersions during solvent removal. A specific example of solvent removal into a region of phase separation of a polymer-colloid suspension will be discussed. The phase boundaries are determined optically and the properties of the resulting concentrated suspensions investigated. The advantage of this approach is the potential to characterize drying of colloidal suspensions without the complexity of three phase contact lines and solid-liquid interfaces.