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Research Papers

Dynamic Characterization of a Valveless Micropump Considering Entrapped Gas Bubbles

[+] Author and Article Information
Songjing Li

e-mail: lisongjing@hit.edu.cn

Jixiao Liu

e-mail: liujixiao@hit.edu.cn
Department of Fluid Control and Automation,
Harbin Institute of Technology,
Harbin 150001, China

Dan Jiang

School of Mechatronics Engineering,
University of Electronic Science and Technology of China,
Chengdu 610000, China
e-mail: jdan2002@163.com

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the Journal of Heat Transfer. Manuscript received June 14, 2012; final manuscript received February 13, 2013; published online July 26, 2013. Guest Editors: G. P. “Bud” Peterson and Zhuomin Zhang.

J. Heat Transfer 135(9), 091403 (Jul 26, 2013) (7 pages) Paper No: HT-12-1288; doi: 10.1115/1.4024461 History: Received June 14, 2012; Revised February 13, 2013

Unexpected gas bubbles in microfluidic devices always bring the problems of clogging, performance deterioration, and even device functional failure. For this reason, the aim of this paper is to study the characterization variation of a valveless micropump under different existence conditions of gas bubbles based on a theoretical modeling, numerical simulation, and experiment. In the theoretical model, we couple the vibration of piezoelectric diaphragm, the pressure drop of the nozzle/diffuser and the compressibility of working liquid when gas bubbles are entrapped. To validate the theoretical model, numerical simulation and experimental studies are carried out to investigate the variation of the pump chamber pressure influenced by the gas bubbles. Based on the numerical simulation and the experimental data, the outlet flow rates of the micropump with different size of trapped gas bubbles are calculated and compared, which suggests the influence of the gas bubbles on the dynamic characterization of the valveless micropump.

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Figures

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Fig. 1

Schematic illustration of a nozzle-diffuser piezoelectric valveless micropump. (a) Cross-sectional view of a nozzle-diffuser piezoelectric valveless micropump. (b) “Supply mode” during pumping. Liquid flows inward to the pump chamber through microchannels, when channel 1 works as a diffuser and channel 2 works as a nozzle. (c) “Pump mode” during pumping. Liquid flows outward to both the inlet and the outlet through microchannels, when channel 1 works as a nozzle and channel 2 works as a diffuser.

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Fig. 2

Structure of a nozzle-diffuser piezoelectric valveless micropump. (a) Micropump after assembling. (b) Explosive view of a nozzle-diffuser piezoelectric valveless micropump. The microchannels are micromachined on PMMA boards. The top layer, the bottom layer, a piezoelectric membrane, an inlet and an outlet pipe are assembled with glue.

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Fig. 3

Pressure-loss coefficient for diffuser and nozzle. The same microchannel will work as diffuser or nozzle in different modes.

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Fig. 4

Experiment setup for the gas bubble observation and pressure pulsation measurement. The 250 Hz 80 V square wave signal is used to drive the piezoelectric membrane. A pressure transducer and the high-speed video camera are adopted for the pressure measurement and image acquisition. The data acquisition board and PC are used for data collection.

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Fig. 5

Experimental results and numerical data of gas bubbles and pressure pulsations. (a) Picture of micropump when gas bubbles occupy about 1/30 of the whole chamber volume (about 1.5 μL). (b) Comparison of simulation result and experimental data when gas bubbles occupy about 1/30 of the chamber volume. (c) Picture of micropump when gas bubbles occupy about 1/8 of the whole chamber volume (about 5 μL). (d) Comparison of simulation result and experimental data when gas bubbles occupy about 1/8 of the chamber volume. (e) Picture of micropump when gas bubbles occupy about 3/8 of the whole chamber volume (about 15 μL). (f) Comparison of simulation result and experimental data when gas bubbles occupy about 3/8 of the chamber volume.

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Fig. 6

Comparison of simulation results with different gas bubble volume. (a) Transient flow rate of the nozzle-diffuser valveless micropump when gas bubbles occupy 0%, 3.33%, 12.5%, and 37.5% of the whole pump chamber volume. (b) Accumulated flow rate (pumped liquid through outlet) for 2 s of the nozzle-diffuser valveless micropump when gas bubbles occupy 0%, 3.33%, 12.5%, and 37.5% of the whole pump chamber volume.

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