Layered liquid-liquid flow in microchannels having selectively modified hydrophilic and hydrophobic walls

Abstract

When two immiscible liquids make contact in a microchannel, the flow pattern is affected by the affinity between channel walls and liquids. In this study, microchannels (200 µm in width and 200 µm in depth) having a Tshaped bifurcation point were fabricated on PMMA plates. The inner walls of the microchannels were modified in a zone-selective manner to be either hydrophilic or hydrophobic, based on verification accomplished via a laser interference fringe technique. The microchannel was placed horizontally, and water and octane were introduced into the upper-side channel (hydrophilic) and into the lower-side channel (hydrophobic), respectively. The experimental results showed that water and octane formed a stable layered flow, and the two liquids were virtually completely separated at the T-shaped section, even when static pressure was intentionally applied to the outlets. CFD simulation, using FLUENT 6.3 software, was performed to explain the role of zone-selective modification of microchannel walls.

Stable Horizontal Interface Formation and Separation of a Water/Oil Flow by Microfluidic Reactor Analyzed by Direct Observation and Numerical Simulation

“…When the upper channel walls become more hydrophilic, and when the lower channel walls become more hydrophobic, stable two-phase laminar flow is formed and good separation is achieved. This indicates that the microreactor fabricated in this work ( = 30°-35° on the hydrophobic walls and 95°-110° on the hydrophilic walls), forms a stable two-layer laminar flow and that separation is achievable over a range of contact angles, as in the case of octane [19]. Fig.…”

“…For observation of fluid behavior, a confocal fluorescence microscopy system (Nikon, Japan) was utilized using an aqueous solution of 50 μmol/L fluorescein instead of pure water. A computational fluid dynamics (CFD) simulation was performed using FLUENT 6.2 (FLUENT Inc., U.S.A.), as previously described [15,16,19]. Fig.…”

Solvent Extraction Behavior of Metal Ions with Calixarene Derivatives by Using a Microreactor

“…The extraction using the micro reactor system was carried out at room temperature. For the extraction experiment, a three-fold greater volume of the organic phase compared to the aqueous phase was loaded to stabilize the interface horizontally [14,15] The microreactor system used in this study.…”

Surface patterning of bonded microfluidic channels

“…For other materials, prebonding modification by TiO 2 is suitable but requires careful alignment of the two halves of the microchip. 64 Therefore, alternative approaches have been developed for bonded microchannels. The introduction of TiO 2 nanoparticle dispersions into a silica microchannel can be used to prepare a photocatalytic TiO 2 layer.…”