Abstract
Using capillary-driven forces as a means to pump and actuate fluids is attractive for many applications including portable, lab-on-a-chip diagnostic systems. However, the lack of reliable and easy-to-integrate means of flow control remains a major challenge for implementing more complex bioassays using capillary microfluidics. This paper presents an easy-to-fabricate, valveless capillary system allowing for high-reliability flow control without using traditional capillary stop or trigger valves. Analytical calculations were used to deduce a design criterion for flow control in the valveless system. Furthermore, electrical analogy modeling was used to analyze and optimize the flow characteristics in the valveless system. Silicon-based test structures and capillary mixing systems were fabricated to check the design criterion and benchmark the electrical analogy model, respectively. Experimental results were in good agreement for the analytically derived flow control criterion. Experimental measurements of the liquid–vapor interface position with respect to time agreed well with the electrical analogy modeling results. The flow control scheme developed in the work provides designers with another means to realize complex fluid processing requirements without the need for traditional valve structures.
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Acknowledgements
The authors would like to acknowledge the valuable help of Edith Grac (Imec, Belgium) for providing the MATLAB® code for tracking the liquid–vapor interface inside the microchannel.
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Taher, A., Jones, B., Fiorini, P. et al. A valveless capillary mixing system using a novel approach for passive flow control. Microfluid Nanofluid 21, 143 (2017). https://doi.org/10.1007/s10404-017-1981-9
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DOI: https://doi.org/10.1007/s10404-017-1981-9