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Research Papers

Improved Flow Rate in Electro-Osmotic Micropumps for Combinations of Substrates and Different Liquids With and Without Nanoparticles

[+] Author and Article Information
Marwan F. Al-Rjoub

Mem. ASME
School of Dynamic Systems,
University of Cincinnati,
598 Rhodes Hall,
Cincinnati, OH 45221
e-mail: alrjoumf@mail.uc.edu

Ajit K. Roy

Air Force Research Laboratory,
Nanoelectronic Materials Branch,
Materials and Manufacturing Directorate,
2941 Hobson Way,
WPAFB, OH 45433-7750
e-mail: ajit.roy@wpafb.af.mil

Sabyasachi Ganguli

Air Force Research Laboratory,
Nanoelectronic Materials Branch,
Materials and Manufacturing Directorate,
2941 Hobson Way,
WPAFB, OH 45433-7750
e-mail: sabyasachi.ganguli.2@us.af.mil

Rupak K. Banerjee

Fellow ASME
School of Dynamic Systems,
University of Cincinnati,
593 Rhodes Hall,
Cincinnati, OH 45221
e-mail: rupak.banerjee@uc.edu

1Corresponding author.

Contributed by the Electronic and Photonic Packaging Division of ASME for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received June 17, 2014; final manuscript received September 19, 2014; published online November 17, 2014. Assoc. Editor: Yi-Shao Lai.

This work is in part a work of the U.S. Government. ASME disclaims all interest in the U.S. Government's contributions.

J. Electron. Packag 137(2), 021001 (Jun 01, 2015) (11 pages) Paper No: EP-14-1059; doi: 10.1115/1.4028746 History: Received June 17, 2014; Revised September 19, 2014; Online November 17, 2014

A new design for an electro-osmotic flow (EOF) driven micropump was fabricated. Considering thermal management applications, three different types of micropumps were tested using multiple liquids. The micropumps were fabricated from a combination of materials, which included: silicon-polydimethylsiloxane (Si-PDMS), Glass-PDMS, or PDMS-PDMS. The flow rates of the micropumps were experimentally and numerically assessed. Different combinations of materials and liquids resulted in variable values of zeta-potential. The ranges of zeta-potential for Si-PDMS, Glass-PDMS, and PDMS-PDMS were −42.5–−50.7 mV, −76.0–−88.2 mV, and −76.0–−103.0 mV, respectively. The flow rates of the micropumps were proportional to their zeta-potential values. In particular, flow rate values were found to be linearly proportional to the applied voltages below 500 V. A maximum flow rate of 75.9 μL/min was achieved for the Glass-PDMS micropump at 1 kV. At higher voltages nonlinearity and reduction in flow rate occurred due to Joule heating and the axial electro-osmotic current leakage through the silicon substrate. The fabricated micropumps could deliver flow rates, which were orders of magnitude higher compared to the previously reported values for similar size micropumps. It is expected that such an increase in flow rate, particularly in the case of the Si-PDMS micropump, would lead to enhanced heat transfer for microchip cooling applications as well as for applications involving micrototal analysis systems (μTAS).

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Figures

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Fig. 1

Schematics of the micropump showing the major components; the PDMS-cast microchannels and the Si substrate

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Fig. 2

Fabrication processes of the PDMS cover (not to scale)

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Fig. 3

ESEM photographs showing the PDMS cover (80×) and a single microchannel wall (500×)

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Fig. 4

(a) Schematics of the experimental flow loop and (b) photograph of the experimental flow loop

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Fig. 5

Experimental setup used to evaluate the P–Q curve of the micropump

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Fig. 6

Fluid flow rates at different voltages for DS water, DI water, 1% Al2O3, and 0.4 mM borax buffer (showing R2 values for two voltage ranges 100–500 V and 100–800 V)

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Fig. 7

Pressure–flow (P–Q) curves for the Si-PDMS micropump using: (a) DI water, (b) DS water, (c) 0.4 mM borax buffer, and (d) 1% Al2O3 nanoparticle solution

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Fig. 8

Fluid flow rates at different voltages for Si-PDMS, Glass-PDMS, and PDMS-PDMS, using DS water

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Fig. 9

Experimental and numerical flow rates for: (a) Si-PDMS section, (b) Glass-PDMS section, and (c) PDMS-PDMS section

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Fig. 10

ESEM photographs of silicon etched microchannels used in earlier designs. (a) Wet etched channels, (b) wet etched channel walls, and (c) dry etched channels.

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Fig. 11

Magnitude of Joule heating in (W) for all liquids at different EOF voltages

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