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Abstract The frequency dependence of electrokinetic particle trapping using large‐area (>mm2) conductive carbon nanofiber (CNF) mat electrodes is investigated. The fibers provide nanoscale geometric features for the generation of high electric field gradients, which is necessary for particle trapping via dielectrophoresis (DEP). A device was fabricated with an array of microfluidic wells for repeated experiments; each well included a CNF mat electrode opposing an aluminum electrode. Fluorescent microspheres (1 µm) were trapped at various electric field frequencies between 30 kHz and 1 MHz. Digital images of each well were analyzed to quantify particle trapping. DEP trapping by the CNF mats was greater at all tested frequencies than that of the control of no applied field, and the greatest trapping was observed at a frequency of 600 kHz, where electrothermal flow is more significantly weakened than DEP. Theoretical analysis and measured impedance spectra indicate that this result was due to a combination of the frequency dependence of DEP and capacitive behavior of the well‐based device.
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This content will become publicly available on December 1, 2026
Dielectrophoretic trapping of particles flowing through an array of conductive cylinders
Dielectrophoresis (DEP) is a label-free electrokinetic method for selectively trapping polarizable particles using non-uniform electric fields. While co-planar electrode systems are common, their inherent DEP force distribution limits throughput. This study presents a computationally efficient framework for modeling two-dimensional DEP-based particle trapping in ordered arrays of conductive cylinders. These cylinders are modeled at a range of sizes, from micrometers to nanometers, to represent microfluidic systems consisting of conductive pillars, nanofibers, etc. Analytical solutions for fluid flow and electric potential were derived using eigenfunction expansions and collocation, then used in a particle tracking model that includes hydrodynamic drag, Brownian motion, and multipolar DEP forces. Although focused on conductive arrays, this framework is extensible to other configurations. This work provides a foundation for future work in the design of high-throughput DEP systems. Both dimensionless and dimensional analyses were performed across a wide range of particle sizes (30 nm to 3 μm), voltages (10 mV to 100 V), and array geometries. No specific optimal cylinder size was found; instead, optimal performance arises from a balance between DEP force distribution and flow through the cylinder array gap. Diamond-oriented arrays exhibited enhanced trapping under moderate dielectrophoretic velocity-to-fluid velocity ratios (up to 39% greater), while square arrays performed better under low-field and large-cylinder conditions (up to 40% greater).
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- Award ID(s):
- 2121008
- PAR ID:
- 10657564
- Publisher / Repository:
- AIP Publishing
- Date Published:
- Journal Name:
- Physics of Fluids
- Volume:
- 37
- Issue:
- 12
- ISSN:
- 1070-6631
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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