where x is the distance from the interface. If ɛw > ɛhc, the charge in the non-polar phase is attracted to its image, but if Ɛw < ɛhc there is repulsion between the charge in the hydrocarbon phase and its image. From Eq. (4), it follows that the charge in the hydrocarbon phase is attracted to the water hydrocarbon interface. In the case of a thin membrane placed in a medium with high dielectric permittivity (Fig. 1), the sum from an infinite number of images must be calculated. Neumke and Lauger [10] estimated the combined Born and image energy of an ion in a thin membrane as follows