Electrowetting-based pico-liter liquid actuation in a glass-tube microinjector

We describe pico-liter liquid actuation in a microinjector. Unlike the most MEMS studies reported before, we used a pulled glass tube as the device structure. The tube can pump and eject based on the principle of electrowetting on dielectrics (EWOD). The pipette was fabricated through a simple process of depositing and patterning a ITO conductive layer and hydrophobic Teflon(R) coatings on the inside and outside of a pulled glass tube. In the experiment, 1000 pl water was introduced within the hydrophilic part of the tube to prime the pump. 500 pico-liter water was then pumped-up at the maximum driving voltage of 1400 V. The obtained increase in pumping pressure was calculated to be 0.6 Pa. The measured actuated volume was compared with the theoretical value to discuss the matter in the proposed fabrication. Since glass-tube pipettes are commonly-used for biological experiments, the fabricated device is compatible with the tools and techniques used in biomedical researches, such as electrophysiological measurement and fluorescence method. (C) 2004 Elsevier B.V. All rights reserved.