Supplementary Information: dissolvable fluidic time delays for programming multi-step assays in instrument-free paper diagnostics

We performed an experiment similar to that of Figure 2 but using saturated sugar solution as the wicking fluid. This system suppresses dissolution of the dried sugar, thus the pore structure of the strips should remain constant during wet-out, and the framework of the conventional Lucas-Washburn relationship should apply (as it does for untreated strips, so long as the meaning of r is not over-interpreted). Strips were prepared by applying different sugar concentrations and drying, followed by wicking saturated sugar solution containing dye into the strips (Figure S1A). Figure S1B shows strips after 2.2 hours. Surprisingly, the wicking rate was comparable for all strips despite a wide range of applied sugar concentrations (0-70% of saturation).