Reconfigurable electrokinetic transport in charge-regulated Janus droplets

Area of Science:

• Microfluidics and interfacial science
• Soft matter physics
• Electrokinetics

Background:

• Janus droplets offer unique electrokinetic transport due to interfacial asymmetry.
• Current systems lack dynamic and reversible control over electrohydrodynamic behavior.
• Engineered surface heterogeneity limits adaptability in droplet manipulation.

Purpose of the Study:

• To introduce a zwitterionically functionalized Janus droplet for programmable electrokinetic transport.
• To enable chemically tunable induced-charge electrophoretic (ICEP) dynamics via pH control.
• To investigate the modulation of electroosmotic slip and electrophoretic motion.

Main Methods:

• Utilized zwitterionic functionalization of Janus droplets for pH-responsive interfacial charge.
• Employed systematic numerical simulations to analyze ICEP dynamics.
• Developed a scaling-based analytical framework to classify electrohydrodynamic responses.

Main Results:

• Demonstrated reversible transitions between vortex-dominated and high-mobility transport regimes based on pH.
• Showcased pH-dependent modulation of ICEP vortex formation and propulsion.
• Revealed that interfacial charge reversal under acidic vs. basic conditions dictates transport characteristics.
• Electric-field polarity reversal offers dynamic switching of vortex formation.

Conclusions:

• Charge-regulated zwitterionic functionalization provides a viable strategy for reconfigurable electrokinetic transport.
• Established a framework for adaptive flow manipulation in microfluidic systems.
• Highlights potential applications in controllable mixing, separation, and programmable droplet transport.