Transportation of Detached Dust Particles

In an ac field a metallic surface may also become recharged, so that charges of different sign will be formed on the particle and the metallic surface these will interact and may increase the adhesive force. Hence, it is more difficult to clean metal surfaces than insulators or semiconductors in an ac field. 

In cleaning a surface it is very important not only to detach the adhering particles, but also to remove them from the area, i.e., to prevent the possibility of their reattachment. A process of this kind occurs when particles are detached in the dc electric field created by a continuous electrode the detached particles execute a shuttle motion between the substrate and the detaching electrode. 

Let us consider the forces acting on a dust particle being detached from the surface. Let us first make an assumption. We shall not consider forces acting tangentially to the dust-laden surface this is equivalent to the assumption that the electric field is uniform in a direction perpendicular to the surface. Then only electric and gravitational forces act on the particle after detachment. The height z to which the particles are raised may be determined from the equation of motion of the particle  

Remembering that the value of Q is directly proportional to r [see formula pC.3)] and that the mass varies as r, we may consider that the hei t to which the particle is raised is inversely proportional to its radius. This means that under otherwise equal conditions small particles will be lifted higher than large ones. 

The following represent the lift of the particles as a function of their size when using a rod electrode (rod diameter, 2 mm distance between rods, 6 mm) with an electrode potential of 20 kV and a distance of 10 mm between the electrode and the dust-laden surface  

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