Microfluidic capillary separation and real-time spectroscopic analysis of specific components from multiphase mixtures.

We present a technique of phase separation suitable for microfluidic systems and demonstrate its efficient integration with a microfluidic optical cell for performing real-time spectrometric measurements on one specific phase from a mixture. We demonstrate that efficient and robust phase separation based on capillarity is possible within a microfluidic chip using either microfabricated capillary channels in polydimethylsiloxane (PDMS) or oil-wet fluoropolymer membranes, allowing for extraction of either the continuous or of the dispersed phases from a multiphase mixture. We analyze the dependence of phase separation efficiency on the operating parameters of the device and observe the presence of a hysteresis cycle during pressure sweeps above a water breakthrough pressure (Pb); we also observe and analyze the reversibility of the oil-wet state of the membrane upon pressure reduction below a reset pressure (Pr < Pb). We test the capillary separation method extensively with several types of organic/water mi...