Consideration of Inner and Outer Phase Configuration in Tube Radial Distribution Phenomenon Based on Viscous Dissipation in a Microfluidic Flow Using Various Types of Mixed Solvent Solutions

Abstract

When mixed solvent solutions, such as ternary water–hydrophilic/hydrophobic organic solvents, water–surfactant, and water–ionic liquid, are delivered into a microspace under laminar flow conditions, the solvent molecules radially distribute in the microspace, generating inner and outer phases. This specific fluidic behavior is termed “tube radial distribution phenomenon”, and has been used in separation technologies such as chromatography and extraction. The factors influencing the configuration of the inner and outer phases in “tube radial distribution phenomenon” using the abovementioned mixed solvent solutions were considered from the viewpoint of viscous dissipation in fluidic flows. When the difference in the viscosity between the two phases was large (approximately >0.73 mPa·s), the phase with the higher viscosity formed as an inner phase regardless of the volume ratio. The distribution pattern of the solvents was supported by the viscous dissipation principle. Contrarily, when the difference was small (approximately <0.49 mPa·s), the phase with the larger volume formed as the inner phase. The distribution pattern of the solvents did not always correspond to the viscous dissipation principle. The current findings are expected to be useful in analytical science including microflow analysis research.