In Fig. (a), we plot counterion distribution across the nanochannel half height for different electric field strengths: for higher electric field strength, the counterion concentration becomes larger (or more localized) at near-wall locations (z = 0 defines the location of the wall). In Fig. (b), we plot the corresponding distribution of the PMETAC monomers, and we find a monomer profile that shows a greater density at near-wall locations for higher electric field strengths. Such a monomer distribution profile, which is commensurate with the corresponding counterion distribution for larger electric field strengths, signifies (as will be discussed in greater details later) that the PE chains are reducing in height at the high electric field. This height reduction in the presence of (a large) applied electric field is typically characterized by the collapse of the PE chains (as elucidated in our previous studies on PAA brushes ), which leads to a reduction in space inside the brush layer and the squeezing out of the counterions from inside the brush to the brush-free bulk [this scenario has been schematically shown in Fig. ]. The squeezing out of the counterions from inside the brush layer will imply that the number of counterions inside the brush layer is significantly smaller than the brush charge, or equivalently, for large applied electric fields, the screening efficiency or SE (of the brush layer by the counterions) will be significantly smaller than 100% (see section S.3.2 in the SI for the procedure to calculate the SE). In Fig. (d), we plot the SE of the PMETAC brush layer (by the counterions) for different strengths of the applied electric field. We find that the SE is nearly 100% for all the values of the applied electric field strength,