Manipulation of dust particles in complex plasmas by electric field

Complex plasmas consist of fine solid particles suspended in a weakly ionized gas. It is often necessary to manipulate particles in a complex plasma of a gas discharge. Popular manipulation methods include modulating the discharge parameters (e.g., discharge voltage or current), using the radiation pressure of a focused laser beam, and using an electrically biased wire or external magnetic field. In the present study, additional electrodes were placed in a plasma of capacitively coupled rf discharge. Polymer microspheres were suspended in the plasma sheath above the lower rf electrode and in the vicinity of the additional electrodes. An ac voltage was applied to the additional electrodes with a frequency higher than the dust plasma frequency but lower than the ion plasma frequency. As a result, ions responded to the applied (screened) ac field and the particles responded to the time-averaged electric field and ion drag force. We discuss various regimes of particle manipulation using this scheme and their applications.