The resulting model of the so-called electrical-double layer (EDL) consists of a charged surface in contact with a liquid region with an enhanced concentration of counterions. 1 This model is widely applied in describing trans-port phenomena in nanofludics,2,4–7 separations based on. Net Surface Charge (Fixed Charge Groups on Surface) : 1. Adsorption (binding of ions) via van der Waals, hydrophobic, or ionic interactions, e. The object might be a solid particle, a gas bubble, a liquid droplet, or a porous body. This region is called the double layer. However, nowadays, it is still a hot topic of investigation, mainly because.