Dielectrophoretic Slide: A Platform for Electrokinetic Characterization of Microparticles.

Dielectrophoresis (DEP) enables label-free particle polarizability quantification via the frequency-dependent Clausius-Mossotti (CM) factor; however, experimental determination of its real component, Re[CM], typically relies on additional confinement systems and complex electrode architectures that limit particle sizes and frequencies. Here, we present a channel-free dielectrophoretic slide that enables Re[CM] determination using unique planar interdigitated electrode array with finger geometry without particle trapping or additional confinement systems. Under AC excitation, time-resolved fluorescence microscopy is used to track individual particle trajectories, from which radial velocities are analytically related to Re[CM]. Measurements using 1 μm carboxylate polystyrene particles reveal a frequency-dependent transition from Brownian- to DEP-dominated transport and yield Re[CM] values between 0.22 and 0.32 across 50-200 kHz, with deviations of ∼0.03 relative to theoretical predictions. This platform provides a simple, reusable, and robust approach for electrokinetic characterization of micro- and nanoparticles, offering a practical alternative to existing techniques.