To better understand the associated counterion distribution, we divide the nanochannel into three regions: inside the brush layer, the brush-bulk interface, and the bulk region of the nanochannel [shown schematically in Fig. ]. The region defined as "inside the brush layer" [shown as yellow rectangles in Fig. (e)] is the region that starts from the nanochannel and extends up to the z value that corresponds to the average brush height. The region defined as the "brush-bulk interface"