Flow of reagents through a stack of four Teflon-patterned paper arrays: adding solutions (here, dyes) in excess to the top paper and allow them to flow by simple gravity through the full stack, then adding an excess of solvent to wash them off. http://www.newswire.ca/en/story/1340115/teflon-not-just-for-pots-and-pans-as-sentinel-bioactive-paper-researchers-find