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Issue 21, 2012
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Systematic characterization of feature dimensions and closing pressures for microfluidic valves produced via photoresist reflow

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Abstract

Multilayer soft lithography (MSL) provides a convenient and low-cost method for fabricating poly(dimethyl siloxane) (PDMS) microfluidic devices with on-chip valves for automated and precise control of fluid flow. MSL casting molds for flow channels typically incorporate small patches of rounded positive photoresist at valve locations to achieve the rounded cross-sectional profile required for these valves to function properly. Despite the importance of these rounded features for device performance, a comprehensive characterization of how the rounding process affects feature dimensions and closing pressures has been lacking. Here, we measure valve dimensions both before and after rounding and closing pressures for 120 different valve widths and lengths at post-rounding heights between 15 and 84 μm, for a total of 1200 different geometries spanning a wide range of useful sizes. We find that valve height and width after rounding depend strongly on valve aspect ratios, with these effects becoming more pronounced for taller and narrower features. Based on the measured data, we provide a simple fitted model and an online tool for estimating the pre-rounding dimensions needed to achieve desired post-rounding dimensions. We also find that valve closing pressures are well explained by modelling valve membranes in a manner analogous to a suspension bridge, shedding new light on device physics and providing a practical model for estimating closing pressures during device design.

Graphical abstract: Systematic characterization of feature dimensions and closing pressures for microfluidic valves produced via photoresist reflow

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Publication details

The article was received on 27 Apr 2012, accepted on 09 Jul 2012 and first published on 11 Jul 2012


Article type: Paper
DOI: 10.1039/C2LC40414A
Citation: Lab Chip, 2012,12, 4287-4295

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    Systematic characterization of feature dimensions and closing pressures for microfluidic valves produced via photoresist reflow

    P. M. Fordyce, C. A. Diaz-Botia, J. L. DeRisi and R. Gomez-Sjoberg, Lab Chip, 2012, 12, 4287
    DOI: 10.1039/C2LC40414A

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