Figure 4.

(a) Fluorescence image of pyranine and Alexa 488 before the surface reaction has saturated. Pyranine, which will have a low barrier to deposit onto the patterned area shows a divergence at the rim, in agreement with the diffusion equation; Alexa 488, which requires a chemical reaction to deposit onto the patterned areas, does not show a divergence. Scale bars 2 μm. (b) Plots of the fluorescence as a function of the radial distance (normalized by the area). This semiquantitative plot demonstrates the spatial differences between adsorption in a reaction limited process vs a barrier-less, diffusion limited adsorption. The plots are normalized against signals obtained from a saturated pattern; the dashed lines show the fluorescence signal for the saturated pattern.