Electrokinetic particle trapping in microfluidic wells using conductive nanofiber mats

Area of Science:

• Microfluidics
• Nanotechnology
• Electrokinetics

Background:

• Dielectrophoresis (DEP) is crucial for particle manipulation in microfluidic devices.
• Large-area electrodes are needed for scalable applications.
• Carbon nanofibers (CNFs) offer nanoscale features for enhanced electric field gradients.

Purpose of the Study:

• Investigate the frequency dependence of electrokinetic particle trapping using large-area CNF mat electrodes.
• Quantify particle trapping efficiency across a range of electric field frequencies.
• Determine the optimal frequency for DEP trapping with CNF electrodes.

Main Methods:

• Fabrication of microfluidic wells with opposing CNF mat and aluminum electrodes.
• Trapping of fluorescent microspheres (1 µm) using varying electric field frequencies (30 kHz–1 MHz).
• Analysis of digital images to quantify particle trapping efficiency.
• Measurement of impedance spectra and theoretical analysis.

Main Results:

• CNF mat electrodes significantly enhanced DEP particle trapping compared to a no-field control across all tested frequencies.
• Maximum particle trapping was observed at 600 kHz.
• This optimal frequency minimizes electrothermal flow effects while maximizing DEP forces.

Conclusions:

• Large-area CNF mat electrodes are effective for electrokinetic particle trapping.
• The frequency dependence of DEP and the device's capacitive behavior influence trapping efficiency.
• The study identifies an optimal frequency for enhanced microfluidic particle manipulation using CNF electrodes.