Continuous Counter-Current Microfluidic Liquid-Liquid Extraction Achieved Using a Pair of Wettable Screen Meshes.

Area of Science:

• Chemical Engineering
• Separation Science
• Microfluidics

Background:

• Continuous counter-current microfluidic liquid-liquid extraction offers efficient separations in a small footprint.
• Stable flow in such devices is challenging due to the need for capillary forces to exceed hydrodynamic forces.

Purpose of the Study:

• To present a novel microfluidic device and flow strategies for stable, long-duration continuous counter-current liquid-liquid extraction.
• To develop and apply methodologies for quantifying the separation performance and theoretical equilibrium stages achieved.

Main Methods:

• Fabrication of a woven mesh screen-based microfluidic device architecture.
• Surface functionalization for conjugate wettability and flow optimization to prevent bubbles and carryover.
• Automated Raman spectroscopy for in-line solute quantitation in a ternary system (tert-butanol in toluene/water).

Main Results:

• Achieved stable, continuous counter-current flow for over 36 hours with good performance.
• Quantified separation performance, observing approximately 37 equilibrium stages (37 ± 13) using Kremser Group Method analysis.
• Demonstrated device efficacy with a ternary system featuring a low solute partition ratio.

Conclusions:

• The novel microfluidic device and flow approaches successfully overcome force-balance challenges for stable counter-current extraction.
• The device architecture is easily fabricated and enables high-performance separations with a significant number of theoretical equilibrium stages.
• This work paves the way for practical applications of continuous counter-current microfluidic extraction.