A comparative study on bubble-driven micropumping in microchannels with square and circular cross sections

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We report experimental evidence that by employing circular flow channels, the maximum pressure head, flow rate and output flow power of a valve-less bubble-driven micropump can be improved by factors of 2.0-2.3, 2.3-2.9 and 3.6-4.6 respectively, when compared with its counterparts with square flow channels having the same hydraulic diameter. It is thus suggested that significant improvements on pumping performance can be achieved by rounding the flow channels of this category of micropumps, which are usually square or rectangular in cross section as fabricated. The geometry-dependent pumping performance is attributed to the different formations of liquid film generated between the gas bubbles and the channel wall. Such liquid films are much thicker in a square flow channel, leading to inferior pumping performance due to unfavorable venting (bubble removal) dynamics and leakage. The venting flow patterns are measured and matched with the two phase flows observed directly in the flow channels to understand their impacts on the pumping characteristics. © 2011 Elsevier B.V. All rights reserved.

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Sensors and Actuators, A: Physical