between the cell and the reservoir. We observe that the linear solution is in good agreement with the nonlinear case for most of the solution support, but slightly underestimates the solution near the microgel center. This behavior is consistent with the approximations inherent to the linearization: towards the cell center, where the charges are located, the |Φ| increases and the linear approximation becomes less accurate, tending to overestimate |Φ|. Furthermore, while for the outside of the microgel, r > a, we only approximate the microion contribution of the electrostatic density, for the inner part, r < a, the acid and basic site contributions are approximated additionally, which results in an overall larger accumulated relative error. Consequently, the derived profiles display a larger inaccuracy around the cell center, as shown in Fig. and. In Figure , we show the cation and anion density profiles, which saturate to a constant equal concentration for r → R. For r → 0, they are increasing and decreasing, respectively, as is expected for a negatively charged microgel.