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

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• 作者：Hiroshi Abe ; Yusuke Imai ; Naoki Tokunaga ; Yasuhiro Yamashita ; Yoshiki Sasaki
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：November 11, 2015
• 年：2015
• 卷：7
• 期：44
• 页码：24492-24500
• 全文大小：600K
• ISSN：1944-8252

文摘

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 螖p_max was 鈭?500 Pa with 12 kV and I = 19 渭A. The smooth surface of the electrodes contributes not only to the formation of a stable electric double layer (EDL) but also to the prevention of charge injection from the electrodes. Polarization pumping derived from the stable EDL enables highly efficient energy transfer without discharging, or damage to the sample and electrodes. The dipole moments of the HFEs were estimated by density functional theory calculations. The hydrostatic pressure was found to be proportional to the difference in the calculated dipole moment between n- and i-HFEs. Numerical simulations were carried out to examine the experimentally obtained electrode gap dependence of the hydrostatic pressure.