Charged nanoparticle in a nanochannel: Competition between electrostatic and dielectrophoretic forces

Nanochannels made in solid-state materials are used for various applications such as nanoparticle separation or DNA manipulation. In this work we examine the effects of the electric and dielectrophoretic forces on a charged nanoparticle confined in a nanochannel. To this end, we solve the Poisson equation for the nanochannel with a wedgelike geometry and consider how channel geometry and electrolyte concentration affect the electrostatic potential distribution and forces acting on nanoparticles of various sizes. On the basis of our calculations, we establish conditions necessary for the particle's attraction to the corners of a channel. We find that for large particles, the net force is attractive only for low concentrations of the electrolyte irrespective of the wedge angle, while small enough particles are attracted to the vertex for either larger electrolyte concentrations or small wedge angle.