Three-dimensional numerical simulation of particle separation using a dusty plasma ratchet

A ratchet can be employed to rectify randomly moving particles, generating directional transport. Taking advantage of the distinct responses of particles with different sizes to the system, bi-dispersed particles can be effectively separated. Based on previous experiments demonstrating the rectification and separation of dust particles in gas-phase plasma, a three-dimensional model is constructed to reveal the physical mechanism behind the separation of bi-dispersed dust particles here. Utilizing plasma fluid simulation and double sine function interpolation, the distribution of plasma parameters in the asymmetric ratchet channel is obtained, which is challenging to measure experimentally. Subsequently, a numerical simulation of the directional transport process of bi-dispersed dust particles in a dusty plasma ratchet is conducted by solving the Langevin equation. The results analyze the forces acting on micro-sized dust particles in the sheath and reproduce the experimental phenomenon of particle separation. The numerical simulation reveals that the bi-dispersed dust particles, suspended at different heights within the sheath, experience asymmetric potentials with opposite orientations, leading to their distinct transport and subsequent separation.