Sample transport and electrokinetic injection in a microchip device for chemical cytometry

Area of Science:

• Microfluidics
• Analytical Chemistry
• Biophysics

Background:

• Sample transport and injection bias are critical in microfluidic devices.
• Existing knowledge is limited for devices combining electroosmosis, electrophoresis, and pressure-driven flow.
• Microfluidic chemical cytometry demands precise sample handling.

Purpose of the Study:

• To evaluate the effects of electric fields, electrophoretic mobility, and pressure-driven flow on sample injection.
• To understand sample transport dynamics in a microfluidic chemical cytometry device.
• To determine the suitability of the device for different analyte types.

Main Methods:

• Experimental evaluation of electric fields (0-300 V/cm), electrophoretic mobilities (10^-4 to 10^-6 cm^2/Vs), and pressure-driven velocities (50-250 μm/s).
• Analysis of a continuous sample stream in a microfluidic device.
• Utilizing COMSOL simulations to predict sample transport.

Main Results:

• Increased electric field strength and electrophoretic mobility improve sample injection.
• COMSOL simulations accurately predict sample transport.
• Pressure-driven flow effects are complex, impacting injection differently based on analyte mobility; high-mobility analytes show robust injection.

Conclusions:

• Device design must consider analyte characteristics, particularly electrophoretic mobility.
• The microfluidic device is well-suited for high-mobility analytes.
• Minimized electrokinetic injection bias and achieved electrophoretic separation were demonstrated for specific peptides.