We investigated an electrohydrodynamic pump that used a gel-coated electrode. An organic liquid that swelled the gel was also used as the working fluid. In this study, we examined 12 liquids. The following properties were found to be preferable for the pumping: (1) the liquid can significantly swell the gel, and (2) it can flow at a high velocity when the electrode is not coated. (c) 2005 Wiley Periodicals, Inc.