Moreover, the exponential decay of the slip length approximates the non-slip condition (see Figure for visualization of the non-slip condition, 𝑙 𝑠 =0). That means that if cations highly increase the interaction between the nanochannel walls and the water, the water transport follows the Hagen-Poiseuille equation. This is a valuable insight as this is experimental support for the use of the Hagen-Poiseuille equation in nanochannels with slip lengths that exceed the channel width. Here it is to be noted that so far, the justification for using the Hagen-Poiseuille equation relied only on molecular-dynamic (MD) simulations and is debated in the literature .