File Name : supplemental_figure_1.tif

Caption : figure s1: dimensions of single unit device. units are in millimeters. a) side view b) bottom view

File Name : supplemental_figure_2.tif

Caption : figure s2: description of backwards flow phenomenon observed in sequential delivery device. a) first reagent is added, mixes with sample well, and equilibrium is established. b) second reagent is added causing the liquid height of the sample to increase, disrupting equilibrium with the first reagent. c) some of the liquid is driven out of the sample well back into the first well until equilibrium is again established.