chemical sciences - adaptive sensors group

Dr. Jungho Kim

Qualifications

Ph.D. - "A study on the longitudinal ultrasonic bonding process for
electronic packaging", Korea Advanced Institute of Science and
Technology, 2004
M.Sc. - "Implementation of Automatic Teaching System for Subassembly
Process in Shipbuilding", Korea Advanced Institute of Science and
Technology, 1996
B.Sc. - Production Engineering, Korea Advanced Institute of Science
and Technology, 1991

Fabrication of microfluidic pump using conductive polymer for low power consumption

Summary

In this paper, we present a low-cost, low-voltage and low-power operating polypyrrole-membrane microfluidic pump with two push button type one-way check-valves for microfluidic applications. This polymeric microfluidic pump is fabricated with a conductive polymer (polypyrrole) modified poly dimethylsiloxane (PDMS) membrane encased into a polymethylmetacrylate (PMMA) structure. The check valves at the inlet and outlet will block unwanted reverse flow in the respective pump phases. The pumping action is induced by an electro-chemical actuated PPy-PDMS membrane. This pump is self-priming and is suitable for lab-on-a-chip applications. Accurate control of the output flow rate can be obtained by changing the actuation frequency. With this pump, a maximum pumping rate of 52㎕/min was achieved using an input power of 55㎽ with ±1.5 volt.

Motivation

Fluid transport is crucial in the development of microanalytical devices. While there are many micropump designs available for micro-nano scale liquid delivery, they generally require high operation voltages and high running current and therefore are very power hungry[1]. In this paper, we present a micropump for small volume fluid delivery. It is small in size, low power and can be easily integrated into microfluidic devices for lab-on–a-chip applications. This design employs polypyrrole (PPy) as the electrochemical actuator to give the mechanical movements required for the pumping action. This PPy actuator can operate below 1V and is extremely energy efficient, it can be operated using a 1.5 volt AA battery and is particularly suitable for microfluidic devices that will be used for long-term field deployments.

Results

Design and fabrication: Fig. 1(a) shows the structure of the designed pump. The micropump consists of two functional PMMA layers; a bottom layer incorporating two push-button type PDMS check-valves and fluidic channels, and a top layer holding a PPy membrane and PDMS diaphragm used for actuation. The PMMA layer was fabricated using a computer aided micro milling machine and the check-valves were molded using a PDMS mixture (Sylgard 184, 10:1 ratio) with PMMA master mold. 100㎛ thick layer of PDMS was fabricated to serve as the actuation diaphragm. The PPy membrane was electrochemically formed using pyrrole (Merck) monomer and propylene carbonate (PC, Aldrich) and LiTFSi salt on a platinum sputter-coated PVDF membrane substrate.² The PPy membrane deforms from convex to concave shape depending on the polarity of the applied voltage. The movement of this PPy membrane induces a push-pull action in the PDMS diaphragm. Fig. 1(b) shows a photograph of the fabricated micropump.

Measurement results: Fig. 2 shows the pumping rate versus the pumping period. Accurate control of the output flow rate can be obtained by changing the actuation period. Fig. 3 shows the measured current profile while switching ±1.5V using a potentiostat. The data was averaged after measuring 10 times under the same conditions. The average power consumption was 55.5mW when the push-pull period was 2 seconds each.

Acknowledgements: This work was funded by Science Foundation Ireland (Grant no. SFI 03/IN.3/1361), the Biotex Project (FP6-2004-1ST-NMP-2) and Korea Research Foundation (KRF-2005-214-D00236)

Figures

Figure 1: (a) The structure of the designed pump. (b) A photograph of the fabricated microfluidic pump.

Fig. 2: Measured pumping rate versus pumping period.

Fig. 3: Measured current profile with switching ±1.5V using potentiostat.

[1] P. Woias, “Micropumps-past, progress and future prospects”, Sen. and Act. B, Vol. 105, P.28-38, 2005.

²S. Hara, T. Zama, W. Takashima, K. Kaneto, “TFSI-dopped Polypyrrole actuator with 26% strain”, The Royal Society of Chemistry, Vol. 14, P. 1516-1517, 2004.

Publications

1. Jung H. Kim, Jihye Lee, and Choong D. Yoo, "Soldering Method Using Longitudinal Ultrasonic", IEEE Trans. on Component, Packaging, and
Manufacturing Technology. Vol. 28, No. 3, pp. 493~498, 2005.
2. Jung H. Kim, Byung C. Kim, Jihye Lee, and Choong D. Yoo, "Thermosonic Bonding of Crossed-Strip Au Bumps", Science and
Technology of Welding and Joining, Vol. 10, No. 5, pp.604~609, 2005.
3. Jihye Lee, Jung H. Kim, and Choong D. Yoo, "Thermosonic Bonding of Lead-free Solder with Metal Bump for Flip-chip Bonding", Journal of
Electronic Materials, Vol. 34, No.1, pp.96~102, 2005.
4. Jung H. Kim, Jihye Lee, and Choong D. Yoo, "Thermosonic Soldering Process with Metal Bump and Lead-free Solder Bumps", J. of Kor. Soc.
of Mech. Engng., Workshop, pp.20 ~ 24, 2004.
5. Byung C. Kim, Jung H. Kim, Jihye Lee, Choong D. Yoo, and Doo S. Choi, "Longitudinal Ultrasonic Bonding of Stripe-type Au Bump", J. of
Kor. Welding Soc., Vol. 22, No. 3, pp. 258 ~ 264, 2004.
6. Jung H. Kim, Jihye Lee, Choong D. Yoo, and Doo S. Choi, "Soldering Process of Au Bump using Longitudinal Ultrasonic", J. of Kor. Welding
Soc., Vol. 22, No. 1, pp. 65 ~ 70, 2004.
7. Jung H. Kim, Jihye Lee, Choong D. Yoo, and Doo S. Choi, "Modeling of Soldering Process using Longitudinal Ultrasonic", J. of Kor.
Welding Soc., Vol. 21, No. 5, pp. 534 ~ 539, 2003
8. Jung H. Kim, Jihye Lee, Choong D. Yoo, and Doo S. Choi, "Development of Ultrasonic Bonding Process for Micro Components", J.
of Kor. Soc. Tech. Plasticity, Vol. 11, No. 7, pp. 596 ~ 600, 2002