Electric Double-layer Forces between Dissimilarly Charged Planar Surfaces in Salt-free Solution

A theoretical study on the electric double-layer force between planar surfaces that may carry dissimilar constant charges or potential in a salt-free solution has been presented in this paper. The results show that the electric double-layer force is always repulsive for positively charged planar surfaces regardless of surface charge density (or potential) and separation; however, a long-range attraction is always existed between oppositely charged surfaces.