As seen in Fig. , the bright spots corresponding to clogs occur within the channels in pristine flow tests. However, after flow tests with particles in NaCl solution or with CTAB pretreatment, bright pixels representing particles or clogs appear mainly in the inlet region, not in the channels. The ratio β quantifies the percentage of particle clogs, or bright pixels, found within the channels. That is, β = 100% means all particles or clogs are found in the channels after a flow test, while β = 0% means all particles or clogs are found in the inlet reservoir.