Fig. 4.

(A and B) Normalized local diffusivity from experiments, $D(x,y)/D_0$, measured in the wide and narrow channels of Fig. 2. (C) Normalized diffusivity, $D_{hyd}(x)/D_0$, vs. $x$. Experimental data and results from finite element calculations are represented by symbols and curves, respectively. Experimentally measured $D_0$ values are $0.29$ and $0.27\mu$m²/s for wide and narrow channels, respectively; the Stokes–Einstein equation predicts a sphere diffusivity of $D_{\text{SE}}=\mathrm{\hspace{0.17em}0.5}\mu$m²/s in an unbounded space.