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Currently, there is very limited information on the electrophoretic behavior of particles at a liquid-liquid interface formed by two conducting liquid solutions. Here, electrophoretic velocities of polystyrene particles at a polyethylene glycol (PEG)-dextran (DEX) interface were investigated in this paper. Experimental results show that the particle at the interface moves in the opposite direction to the applied electric field, with a velocity much lower than that in the PEGrich phase and a litter larger than that in the DEX-rich phase. Similarly to the movement in Newtonian fluids, the velocity increases linearly with the increase in the applied electric field. Different to particle electrophoresis in Newtonian fluids, the velocities of the particles at the PEG-DEX interface increase linearly with the decrease in particle's diameters, implying a possible size-based particle differentiation at an interface.

Building the optical filtration function into a microfluidic chip is a promising way for simplifying the optical detection system of a microfluidic device. In this paper, a PDMS microfluidic chip...