Towards Microfluidic Separation Processes Using Switchable Hydrophilicity Solvents

CO2 - Switchable Hydrophilicity solvents (SHS) are liquid solvents that are highly hydrophobic at room conditions and become hydrophilic when exposed to CO2; this phenomenon is, in most cases, reversible. This class of solvents has gained popularity because they offer opportunities in many processes such as liquid-liquid separations. In this work, a CO2 - SHS, 2-2-Dibutylaminoethanol (DBAE), was chosen to study the switching phenomenon using polydimethylsiloxane (PDMS) microfluidic devices made by soft lithography. The compatibility of this solvent with PDMS was tested by observations at the scale of a centimetric piece of PDMS, and at the scale of a microfluidic channel (approx. 50 µm in height). No visible swelling of the polymer matrix was observed on a macroscopic scale, while we demonstrated DBAE pervaporation, PDMS oligomer extraction, and accumulation of a fluorescent compound at the microfluidic channel scale.