Estimated depth concentration of uranine in the hydrogel using one-shot measurements.

(a) Estimated concentration in single hydrogel layers containing 5, 50, and 100 μmol/L uranine. Broken lines show the theoretical values. (b) Estimated concentration in double hydrogel layers at different uranine concentrations (50 and 25 μmol/L). A non-permeated transparent layer 10 μm in length was placed at the interface to prevent mass transport through the interface.