Department of Biochemistry and Biophysics, University of California San Francisco, 1700 4th Street Byers Hall Room 403, San Francisco, CA 94158, USA.
Lab Chip. 2012 Nov 7;12(21):4287-95. doi: 10.1039/c2lc40414a.
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.
多层软光刻（MSL）为制造具有片上阀的聚二甲基硅氧烷（PDMS）微流控器件提供了一种方便且低成本的方法，可实现对流体流动的自动化和精确控制。用于流道的 MSL 铸造模具通常在阀位置包含小的圆形正光刻胶补丁，以实现这些阀正常工作所需的圆形横截面轮廓。尽管这些圆形特征对于器件性能很重要，但对于圆角过程如何影响特征尺寸和关闭压力的全面表征一直缺乏。在这里，我们测量了 1200 种不同几何形状的圆角前后的阀尺寸和关闭压力，这些几何形状的后圆角高度在 15 到 84μm 之间，阀宽度和长度的 120 个不同值，涵盖了广泛的有用尺寸范围。我们发现圆角后阀的高度和宽度强烈依赖于阀的纵横比，对于更高和更窄的特征，这些影响更加明显。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，用于估计实现所需圆角后尺寸所需的预圆角尺寸。我们还发现，通过类似于悬索桥的方式对阀膜进行建模，可以很好地解释阀的关闭压力，这为器件物理提供了新的认识，并为在器件设计过程中估计关闭压力提供了实用的模型。
