Microelectrophoresis in a laser trap: a platform for measuring electrokinetic interactions and flow properties within...

Area of Science:

• Physics
• Chemistry
• Microfluidics

Background:

• Accurate measurement of forces on charged particles is crucial for understanding microfluidic phenomena.
• Existing methods for zeta potential and flow profiling often lack precision or require complex sample preparation.

Purpose of the Study:

• To develop and validate a combined microelectrophoresis and optical tweezer system for precise electric force measurements.
• To demonstrate the capability of this apparatus for accurate zeta potential determination and microfluidic flow profiling.

Main Methods:

• Utilized a combination of microelectrophoresis and laser-trap (optical tweezer) methodology.
• Employed stop-flow techniques for potential kinetic studies.
• Characterized hydrodynamic and electro-osmotic flow within microchannels.

Main Results:

• Achieved submillivolt accuracy and high temporal resolution in zeta potential measurements.
• Successfully profiled position and frequency-dependent hydrodynamic and electro-osmotic flow in microchannels without fluorescent markers.
• Demonstrated good agreement with electrophoretic flow theory, including retardation effects.

Conclusions:

• The developed microelectrophoresis and laser-trap system offers a powerful tool for precise characterization of microfluidic systems.
• This methodology facilitates high-resolution studies of particle dynamics, zeta potential, and fluid flow in microchannels.
• Potential for single-molecule sensitivity in adsorption and enzyme kinetics studies was highlighted.