Fabrication and characterization of a bidirectional valveless peristaltic micropump and its application to a flow-type immunoanalysis

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Abstract

A planar bidirectional valveless peristaltic micropump for controlling biological sample fluids was designed with a very simple structure and fabricated employing MEMS technologies including deep reactive ion etching (DRIE) process in silicon, chemomechanical polishing (CMP), and silicon–glass anodic bonding. The proposed micropump was able to control the flow bidirectionally at the rate of ∼12 μl/min (20 nl/stroke) for water and ∼60 μl/min (100 nl/stroke) for air with an operation frequency of 10 Hz at a voltage of 120 Vpp. Actuation modeling of the PZT-glass actuator was performed using the CoventorWare, and the simulation results agreed well with the experimental measurements. In addition, the fabricated micropump was used in the setup for flow-type analysis and was found adequate in the electrochemical immunosensing by biocatalyzed precipitation.

Introduction

Recently, there has been an increased interest in microfluidic systems, like micro total analysis systems (μTAS) and microdosage systems, which use MEMS technologies to create advantages, i.e., high throughput, rapid response, and reduction in samples and reagents applied [1], [2], [3]. One of the main components in a microfluidic system is a micropump. Due to the increasing need from the biochemical and biomedical industries, various efforts to manipulate minute amount of samples have been attempted [1], [4], [5]. However, for practical applications, advanced micropumps are still needed that can reliably control liquids in a microliter range with directional contollability and simple structure.

Concerning the practical use of pumps in microfluidic systems, like μTAS, lab on a chip (LOC), and flow injection analysis (FIA), there are a number of challenges that we should take up. The integration between different components, such as valves and reservoirs with pumps, the design of efficient liquid pumping strategies that do not expose analytes to high electrical charges (overheating), and the settlements of problems arising from surface tension, air bubbles, and the clogging of microchannels with trapped small particles or precipitates are typical examples [6], [7], [8], [9], [10], [11], [12], [13], [14].

Accordingly, this paper shows a complete set of experimental results on fluidic pumping properties of a planar valveless peristaltic micropump fabricated for the purpose of controlling liquid or air fluids precisely with directional regulation under a microliter range. Our method differs from that of Olsson [3], [15] in the specific method of operation and that of Cao et al. [16] in the location and operational scheme of piezoactuators. The proposed micropump presents a number of merits such as simple structure and reduction in the fabrication steps in terms of device fabrication, chemical resistance and compatibility to biological fluid from the use of external piezoactuator, and applicability to the biomicrosystems including polymerase chain reaction (PCR) and immune sensing systems [17]. Fabrication and operational properties of the micropump with a model study of implementing the device for the flow-type immunoassay have been reported in this paper.

Section snippets

Experimental

A schematic diagram of the proposed valveless peristaltic PZT micropump is shown in Fig. 1(a). The micropump consists of an inlet port, three pumping chambers, three PZT actuators on each chambers, flow microchannels connecting adjacent chambers, and an outlet port. The fabricated micropump is shown in Fig. 1(b). A three-dimensional modeling was employed to perform a mechanical simulation of the microscale actuation in the designed micropump before fabricating the device, as shown in Fig. 2.

Results and discussion

To determine the electromechanically-coupled field effects from PZT actuation, the CoventorWare simulator was used, containing relevant elements for this type of simulation. A three-dimensional model of the circular PZT-glass structure, as shown in Fig. 2, was used for the simulation. The circumference sidewalls of the Pyrex glass membrane were clamped, while those of the PZT disk actuators were remained free. And the bottom surface of the PZT actuators was in close contact to the top surface

Conclusion

A planar bi-directional valveless peristaltic micropump for controlling biological fluids was designed with a simple structure only involving two masks and fabricated employing MEMS technologies, i.e. DRIE in silicon and silicon/glass anodic bonding. A simulation of the proposed PZT-glass membrane actuator was performed, and the comparison with experimental measurements exhibited a good agreement. The fabricated micropump was able to control the water flow rate at ∼12 μl/min (20 nl/stroke), with

Acknowledgements

This work has been financially supported by the Ministry of Information and Communication of Korea. H.C.Y. is grateful to Ajou University for financial support through Research Initiation Program, 2003. The authors would like to thank Mr. Seungoh Han at Davan Tech Co. for his advice with the simulation.

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