Tunable Electrokinetic Motion of Charged Nanoparticles in an Aqueous Solution Using Interdigitated Microelectrodes

Electrokinetic phenomena offer promising tools for the manipulation of micro- and nanoparticles in liquid media. However, most existing techniques rely on complex configurations and are often limited to particle separation based on large size differences or distinct material properties. Here, we present a simple and tunable method for spatial control and separation of nanoparticles using interdigitated electrodes under AC electric fields. Our approach exploits subtle differences in the electroosmotic and dielectrophoretic responses of particles with small size variations but identical material compositions. By adjusting the frequency and amplitude of the applied voltage, particles can be selectively directed and accumulated at designated regions of the device, enabling precise control over their positioning and segregation. We demonstrate the effectiveness of our method using micro- and nanoparticles composed of the same material, achieving accurate spatial separation based solely on their electrokinetic behavior. This technique offers a low-cost, easily integrable platform for diverse applications, including cell manipulation, water purification, and targeted drug delivery.