Abstract
The thickness and the effects of electrical double layer on micro capillaries are analyzed in the present study. The distribution of the electric potential in the double layer is first determined by solving the Poisson-Boltzmann equation in cylindrical coordinates using the power series method. A definition for the double layer effective thickness is introduced based on 1% relative electrical potential at the artificial cut-off boundary. In this approach, a coefficient, being independent of the non-dimensional Debye-Huckel length, is introduced and is applied successfully to assess the double layer effective thickness at the solid-liquid interface. The results show that the double layer effective thickness is 4.7 times greater than that of the traditional value based on the thickness of the ionic atmosphere at the ion-liquid interface. The results appear to be in close agreement with Hunter's suggestion. Example is also given to illustrate the applications of the present study.