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. Author manuscript; available in PMC: 2012 Feb 1.
Published in final edited form as: Sens Actuators A Phys. 2011 Feb 1;165(2):310–315. doi: 10.1016/j.sna.2010.10.002

Figure 2.

Figure 2

Experimental visualizations of concentration fields in the millichannel about the silica frit (225 nm mean pore radius). We show visualizations at three borate ionic strengths (10, 1, 0.1 mM) and an applied current of 25 μA. The x-axis represents axial position along the borosilicate millichannel which houses the frit, and the ordinate is elapsed time (current is applied at 10 s). The colormap represents the concentration enrichment factor. In all realizations, the anode and cathode surfaces are at ~ 0 and 5.5 mm, respectively, and the frit between 2 and 3 mm. a) At 10 mM borate, no CP is observed. The frit and electrode boundaries are shown as dashed lines. b) At 1 mM, CP zones observably form but remain local to the frit surfaces. Additionally, a barely noticeable, apparently stationary depletion zone forms near the cathode surface. c) At 0.1 mM, CP fronts clearly propagate from the frit. Also, propagating enrichment and depletion zones are sourced by the anode and cathode, respectively.