Analytical and Bioanalytical Chemistry

, Volume 382, Issue 3, pp 817–824 | Cite as

An electro-osmotic micro-pump based on monolithic silica for micro-flow analyses and electro-sprays

Original Paper
First Online:
Received:
Revised:
Accepted:

Abstract

A high-pressure electro-osmotic micro-pump fabricated by a sol–gel process is reported as a fluid-driving unit in a flow-injection analysis (FIA) system. The micro FIA system consists of a monolithic micro-pump on a glass slide (2.5×7.5 cm), a micro-injector, and a micro-sensor (2.5×1.5 cm). The monolithic silica matrix has a continuous skeleton morphology with micrometer-sized through-pores. The micrometer-size pores with a large negative surface charge density build up a large pressure under a DC electric field to drive fluid through the downstream units. A novel Nafion joint for the downstream cathode eliminates flow into the electrode reservoir and further enhances pressure build-up. The measured pump-pressure curve indicated a maximum pressure of 0.4 MPa at flow rate of 0.4 μL min−1 at 6 kV. Despite the large voltage, the small current transmission area through the monolith produced a negligible current (less than 100 μA) that did not generate bubbles or ion contaminants. The flow rate can be precisely controlled in the range 200 nL to 2.5 μL min−1 by varying the voltage from 1 to 6 kV. The high pump pressure and the large current-free DC field also enabled the pump to act as an electro-spray interface with a downstream analytical instrument.

Keywords

Electroosmotic micropump Monolith Sol–gel Bio-sensor Flow-injection analysis Electrospray. 
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Notes

Acknowledgments

We thank Dr Albert E. Miller, University of Notre Dame, for use of his electrochemical instrument; Dr William Boggess, University of Notre Dame, for the injector used in this study, and Mr Katsuyashi Hayashi, NTT Microsystem Integration Labs, for valuable discussion on the sensor. This work is supported by the Center for Microfluidics and Medical Diagnostics at the University of Notre Dame.

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Copyright information

© Springer-Verlag 2005

Authors and Affiliations

  1. 1.Center for Microfluidics and Medical Diagnostics, Department of Chemical and Biomolecular EngineeringUniversity of Notre DameUSA

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