Date on Master's Thesis/Doctoral Dissertation

5-2024

Document Type

Master's Thesis

Degree Name

M.S.

Department

Mechanical Engineering

Degree Program

Mechanical Engineering, MS

Committee Chair

Williams, Stuart

Committee Member

Brehob, Ellen

Committee Member

Cohn, Robert

Author's Keywords

dielectrophoresis; electrokinetics; electrohydrodynamics; nanofibers; microparticles

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 – 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 (ET) flow is more significantly weakened than DEP. This result indicates the contribution to particle trapping by ET flow is not exclusively positive.

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