Electrokinetic micro- and nanoparticle trapping using electrospun conductive nanofiber mats

Dielectrophoresis (DEP) is a microfluidic technique that can collect and trap micro- and nanoparticles by subjecting them to nonuniform electric fields. The DEP force is proportional to the gradient of the electric field squared (▽E²), so DEP is dependent upon field nonuniformity. DEP particle trapping suffers from low throughput because field nonuniformities are typically focused at sharp features such as electrode edges. Conductive nanofiber mats can distribute high DEP forces across a mesh of sharp features. Our nanofiber mats are created using electrospinning. Carbon nanotubes are added to a solution of polyacrylonitrile dissolved in N, N-dimethyl formamide; this solution is electrospun and then pyrolyzed. The conductive nanofibers have diameters of 267 ± 94 nm and conductivity between 2 – 5 S/cm. Proof-of-concept experiments with the mats demonstrated voltage and frequency dependence of DEP particle trapping, and we successfully trapped particles as small as 20 nm in diameter. Our recent experiments have incorporated the mats into microfluidic wells to investigate DEP particle trapping across larger mat surface areas. Analysis of the mats with trapped particles provides insight for comparison of trapping at different particle sizes, applied voltages, and field frequencies. We suspect electrohydrodynamic flows significantly affect particle trapping in these experiments.