Issue 6, 2008

Micropumping of liquid by directional growth and selective venting of gas bubbles

Abstract

We introduce a new mechanism to pump liquid in microchannels based on the directional growth and displacement of gas bubbles in conjunction with the non-directional and selective removal of the bubbles. A majority of the existing bubble-driven micropumps employs boiling despite the unfavorable scaling of energy consumption for miniaturization because the vapor bubbles can be easily removed by condensation. Other gas generation methods are rarely suitable for micropumping applications because it is difficult to remove the gas bubbles promptly from a pump loop. In order to eradicate this limitation, the rapid removal of insoluble gas bubbles without liquid leakage is achieved with hydrophobic nanopores, allowing the use of virtually any kind of bubbles. In this paper, electrolysis and gas injection are demonstrated as two distinctively different gas sources. The proposed mechanism is first proved by circulating water in a looped microchannel. Using H2 and O2 gas bubbles continuously generated by electrolysis, a prototype device with a looped channel shows a volumetric flow rate of 4.5–13.5 nL s−1 with a direct current (DC) power input of 2–85 mW. A similar device with an open-ended microchannel gives a maximum flow rate of ∼65 nL s−1 and a maximum pressure head of ∼195 Pa with 14 mW input. The electrolytic-bubble-driven micropump operates with a 10–100 times higher power efficiency than its thermal-bubble-driven counterparts and exhibits better controllability. The pumping mechanism is then implemented by injecting nitrogen gas bubbles to demonstrate the flexibility of bubble sources, which would allow one to choose them for specific needs (e.g., energy efficiency, thermal sensitivity, biocompatibility, and adjustable flow rate), making the proposed mechanism attractive for many applications including micro total analysis systems (μTAS) and micro fuel cells.

Graphical abstract: Micropumping of liquid by directional growth and selective venting of gas bubbles

Article information

Article type
Paper
Submitted
04 Jan 2008
Accepted
26 Mar 2008
First published
24 Apr 2008

Lab Chip, 2008,8, 958-968

Micropumping of liquid by directional growth and selective venting of gas bubbles

D. D. Meng and C. “. Kim, Lab Chip, 2008, 8, 958 DOI: 10.1039/B719918J

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