Highly Efficient Electrohydrodynamic Pumping: Molecular Isomer Effect of Dielectric Liquids, and Surface States of Electrodes

Highly efficient electrohydrodynamic (EHD) pumping was obtained by a combination of a dielectric liquid having a molecular isomer and electrodes with a smooth surface. Four kinds of surface states of Cu electrodes were processed by conventional mechanical polishing, fine diamond paste polishing, chemical etching and Au vapor deposition. A series of hydrofluoroether liquids (HFEs) were used as dielectric liquids: C3F7OCH3 (HFE-7000), C4F9OCH3 (HFE-7100), C4F9OC2H5 (HFE-7200), C6F13OCH3 (HFE-7300), and C5H5F6OC3HF6 (HFE-7600). The coexistence of normal (n-) and isomer (i-) HFEs and their molar fractions were examined by NMR spectroscopy. Among the dielectric liquids, the hybrid n- and i-HFE-7600 showed highly efficient EHD pumping, where the electric current, I, was sufficiently suppressed by the smooth surface of the electrodes. The maximum hydrostatic pressure Δpmax was ∼7500 Pa with 12 kV and I = 19 μA. The smooth surface of the electrodes contributes not only to the formation of a stable electric double...