where, for our purpose here, [𝑆] value may be approximated by [𝑆] value at 𝜁 , defined by the intersection of the two lines figuring the slopes of 𝑆 concentration profile on either side of the enzymatic layer in the conformal space (Fig. ). 𝜁 is much smaller than 𝛿 since its value is by definition smaller than that of the thickness of the thin enzymatic coating (see Fig. ). Hence, Eq.( ) can be readily simplified into: