Systematic characterization of feature dimensions and closing pressures for microfluidic valves produced via photoresist reflow
Systematic characterization of feature dimensions and closing pressures for microfluidic valves produced via photoresist reflow
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DOI：
10.1039/c2lc40414a
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发表时间：
2012-01-01
期刊：
影响因子：
6.1
通讯作者：
Gomez-Sjoberg, R.
中科院分区：
文献类型：
--
作者：
Fordyce, P. M.;Diaz-Botia, C. A.;Gomez-Sjoberg, R.
多层软光刻技术(MSL)为制备具有片上阀门的聚二甲基硅氧烷(PDMS)微流控器件提供了一种方便、低成本的方法，可实现流体流量的自动化和精确控制。用于流道的MSL铸造模具通常在阀门位置包含小片圆形正性光致抗蚀剂，以获得这些阀门正常运行所需的圆形横截面轮廓。尽管这些圆角特征对于器件性能很重要，但圆角过程如何影响特征尺寸和闭合压力的全面表征一直缺乏。在这里，我们测量了120种不同宽度和长度的阀门在圆整前后的尺寸和关闭压力，圆角后的高度在15 mm到84 mm之间，总共有1200种不同的几何形状，涵盖了各种有用的通径。我们发现，四舍五入后气门的高度和宽度强烈地依赖于气门的纵横比，这些影响对于较高和较窄的特征变得更加明显。基于测量数据，我们提供了一个简单的拟合模型和一个在线工具，用于估计达到所需的后舍入尺寸所需的舍入前尺寸。我们还发现，通过以类似于悬索桥的方式对阀膜进行建模，可以很好地解释阀门关闭压力，这为设备物理提供了新的认识，并为在设备设计过程中估计关闭压力提供了一个实用的模型。
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 mm, 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.