EDL configuration on a dissimilarly charged protrusion array via double Fourier series and perturbation method

In this study, through the extension of an one-dimensional, dissimilarly charged protrusions surface model set up in our previous work, a novel dissimilarly charged protrusion array (DCPA) model immersed in an electrolyte solution, which could simulate realistically both the surface morphology and the surface charged condition profoundly concerned on a biological cell membrane, or on the surface of a micro-scale, modified particle used in biomedical engineering and water treatment, is proposed. Considering the condition of small protrusions, the electrical potential field due to the electrical double layer (EDL) on DCPA model is solved semi-analytically using both the double Fourier series and the perturbation method. The analysis from the numerical result reveals that, a small, dissimilarly charged protrusion can lead to a steep variation in the local EDL configuration, especially compared with that in the condition when the charged surface is taken roughly as a flat surface using a lumped, mean surface charge density.