Liquid–liquid phase separation: characterisation of a novel device capable of separating particle carrying multiphase flows

Abstract

Capillary forces on the microscale are exploited to create a continuous flow liquid–liquid phase separator. Segmented flow regimes of immiscible fluids are generated and subsequently separated into their component phases through an array of high aspect ratio, laser machined, separation ducts (36 µm wide, 130 µm deep) in a planar, integrated, polytetrafluoroethylene (PTFE) microdevice. A controlled pressure differential across the phase separator architecture facilitates the selective passage of the wetting, organic, phase through the separator ducts, enabling separation of microfluidic multiphase flow streams. The reported device is demonstrated to separate water and chloroform segmented flow regimes at flow rates up to 0.4 ml min⁻¹. Separation efficiency is quantified over a range of flow rates and applied pressure differentials, characterising device behaviour and limits of operation. Experimental measurements and observations are supported by theoretical hydrodynamic and capillary pressure modelling. The influence of material properties and geometric design parameters on phase separation is quantified and optimisation strategies proposed. The novel ability of the membrane free device to separate an organic phase containing suspended microparticulates, from an aqueous phase, is also demonstrated.