Microfluidic lab-on-a-chip devices are usually fabricated using replica molding, with poly(dimethylsiloxane) (PDMS) casting on a mold. Most common techniques used to fabricate microfluidic molds, such as photolithography and soft lithography, require costly facilities such as a cleanroom, and complicated steps, especially for the fabrication of three-dimensional (3D) features. For example, an often-desired 3D microchannel feature consists of intersecting channels with depth variations. This type of 3D flow focusing geometry has applications in flow cytometry and droplet generation. Various manufacturing techniques have recently been developed for the rapid fabrication of such 3D microfluidic features. In this paper, we describe a new method of mold fabrication that utilizes water jet cutting technology to fabricate free-standing structures on mild steel sheets to make a mold for PDMS casting. As a proof-of-concept, we use this fabrication technique to make a PDMS chip that has a 3D flow focusing junction, an inlet for the sample fluid, two inlets for the sheath fluid, and an outlet. The flow focusing junction is patterned into the PDMS slab with an abrupt, nearly stepwise change to the depth of the microchannel junction. We use confocal microscopy to visualize the 3D flow focusing of a sample flow using this geometry, and we also use the same geometry to generate water-in-oil droplets. This alternative approach to create microfluidic molds is versatile and may find utility in reducing the cost and complexity involved in fabricating 3D features in microfluidic devices.

中文翻译：

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一种新颖的磨料水射流加工技术，用于快速制造三维微流体组件。


微流控芯片实验室设备通常采用复制成型法制造，并在模具上浇注聚（二甲基硅氧烷）（PDMS）。用于制造微流体模具的最常见技术（例如光刻和软光刻）需要昂贵的设施（例如洁净室）和复杂的步骤，特别是对于三维（3D）特征的制造。例如，经常需要的 3D 微通道特征由具有深度变化的交叉通道组成。这种类型的 3D 流聚焦几何结构可应用于流式细胞术和液滴生成。最近已经开发出各种制造技术来快速制造此类 3D 微流体特征。在本文中，我们描述了一种新的模具制造方法，该方法利用水射流切割技术在低碳钢板上制造独立式结构，以制造用于 PDMS 铸造的模具。作为概念验证，我们使用这种制造技术制造了一个 PDMS 芯片，该芯片具有 3D 流聚焦接头、一个样本流体入口、两个鞘液入口和一个出口。流动聚焦连接点被图案化到 PDMS 板中，微通道连接点的深度发生突然的、几乎逐步的变化。我们使用共焦显微镜来可视化使用这种几何形状的样品流的 3D 流聚焦，并且我们还使用相同的几何形状来生成油包水液滴。这种创建微流体模具的替代方法用途广泛，并且可能有助于降低微流体设备中制造 3D 特征的成本和复杂性。