Simple Multi-level Microchannel Fabrication by Pseudo-Grayscale Backside Diffused Light Lithography.
Simple Multi-level Microchannel Fabrication by Pseudo-Grayscale Backside Diffused Light Lithography.
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DOI：
10.1039/c3ra43834a
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发表时间：
2013-11-14
期刊：
影响因子：
3.9
通讯作者：
Takayama S
中科院分区：
文献类型：
--
作者：
Lai D;Labuz JM;Kim J;Luker GD;Shikanov A;Takayama S
微流体中的多级通道特征的光刻是费力的和/或昂贵的。灰度光刻主要与正性光致抗蚀剂和常规正面曝光一起使用，但是所需的灰度掩模通常是昂贵的，并且正性光致抗蚀剂通常不用于微流体快速原型制作。在这里，我们介绍了一种简单而廉价的替代方案，使用伪灰度（pGS）光掩模结合背面漫射光光刻（BDLL）和常用的负性光刻胶，SU-8。BDLL可以产生平滑的多级通道的逐渐变化的高度，而不使用真正的灰度掩模，因为使用漫射光。由于曝光是通过载玻片进行的，因此光致抗蚀剂从基板侧向上交联，从而能够从甚至未旋转的光致抗蚀剂层制造出良好限定且稳定的结构。除了提供独特的结构和能力之外，该方法还与以低成本创建有用工具的“车库微流体”概念兼容，因为pGS BDLL可以仅使用热板和UV透照仪进行：生物实验室中常见的设备。不需要昂贵的旋涂机或准直UV对准器。为了证明pGS BDLL的适用性，构建了多种堰式细胞捕集器，单次UV暴露以将癌细胞（MDA-MB-231，大小为10-15 μm）与红细胞（RBC，大小为2-8 μm）以及卵泡簇（大小为40-50 μm）与癌细胞（MDA-MB-231，大小为10-15 μm）分离。
Photolithography of multi-level channel features in microfluidics is laborious and/or costly. Grayscale photolithography is mostly used with positive photoresists and conventional front side exposure, but the grayscale masks needed are generally costly and positive photoresists are not commonly used in microfluidic rapid prototyping. Here we introduce a simple and inexpensive alternative that uses pseudo-grayscale (pGS) photomasks in combination with backside diffused light lithography (BDLL) and the commonly used negative photoresist, SU-8. BDLL can produce smooth multi-level channels of gradually changing heights without use of true grayscale masks because of the use of diffused light. Since the exposure is done through a glass slide, the photoresist is cross-linked from the substrate side up enabling well-defined and stable structures to be fabricated from even unspun photoresist layers. In addition to providing unique structures and capabilities, the method is compatible with the “garage microfluidics” concept of creating useful tools at low cost since pGS BDLL can be performed with the use of only hot plates and a UV transilluminator: equipment commonly found in biology labs. Expensive spin coaters or collimated UV aligners are not needed. To demonstrate the applicability of pGS BDLL, a variety of weir-type cell traps were constructed with a single UV exposure to separate cancer cells (MDA-MB-231, 10-15 μm in size) from red blood cells (RBCs, 2-8 μm in size) as well as follicle clusters (40-50 μm in size) from cancer cells (MDA-MB-231, 10-15 μm in size).