复乳代使用聚二甲基硅氧烷（PDMS）同轴流量聚焦设备
Summary
Microfluidic double emulsions generation typically involves devices with patterned wettability or custom-fabricated glass components. Here we describe the fabrication and testing of an all polydimethylsiloxane (PDMS) double emulsion generator that does not require surface treatment or complicated fabrication processes, and is capable of producing double emulsions down to 14 µm.
Abstract
Double emulsions are useful in a number of biological and industrial applications in which it is important to have an aqueous carrier fluid. This paper presents a polydimethylsiloxane (PDMS) microfluidic device capable of generating water/oil/water double emulsions using a coaxial flow focusing geometry that can be fabricated entirely using soft lithography. Similar to emulsion devices using glass capillaries, double emulsions can be formed in channels with uniform wettability and with dimensions much smaller than the channel sizes. Three dimensional flow focusing geometry is achieved by casting a pair of PDMS slabs using two layer soft lithography, then mating the slabs together in a clamshell configuration. Complementary locking features molded into the PDMS slabs enable the accurate registration of features on each of the slab surfaces. Device testing demonstrates formation of double emulsions from 14 µm to 50 µm in diameter while using large channels that are robust against fouling and clogging.
Introduction
双乳液包括由一中间，不混溶流体层从载体相分离的液滴的，并且是特别令人感兴趣的，因为它们在工业，制药潜在用途，以及生物应用1。在某些情况下，以封装高价值的化合物在双乳剂的核心的能力使材料受到保护和释放以控制的方式。例如，药物可能不适合于外部载体流体 2的溶解度的条件下被封装。此外，中间层的油可以被用作用于药物，化妆品，和营养物质3的封装和递送的胶囊模板。在生物学中，双乳液，可以在高通量筛选有用的，因为它们允许进行子纳升实验数量庞大出来，然后检测和分选使用荧光激活细胞分选（FACS）仪器4,5。
ENT“>双乳液具有所需的性能特性的设计需要的双乳液的尺寸，组合物和均匀性的精确控制。虽然散装乳化过程，如膜乳化，在工业中使用，所得到的乳液是高度多分散的，显示出各种各样的功能特性1。液滴的微流体的字段被自然地适合单分散乳剂的产生与仔细控制组合物6。微流体双乳液生成已经实现了两个主要策略，顺序降制作和玻璃毛细管流聚集。双乳剂可以在使用两步骤降决策过程的平面PDMS的设备来产生。首先，含水包油乳液用的是水包油滴制作具有疏水通道壁的装置的区域。接着创建的，该乳液可以是流入或重新注入与适用于水包油型亲水墙壁下降，使得区域落制作4。然而，PMDS的亲水性表面处理需要额外的制造步骤和通常是暂时的7。最可控和可重复的方法，以形成双乳液是通过共轴流聚焦，一种技术使用玻璃毛细管微流体，由此形成含有三个阶段的同心射流通过一个小孔剪切以产生单分散的液滴8首创。这种技术允许用于生产液滴比通道尺寸小得多的，与双乳液是各相的流速的函数的精确大小和组成。液滴和信道的大小和保护性外鞘流之间的大的差异防止液滴从接触通道壁，使表面处理不必要。然而，这种玻璃设备需要锥形毛细管提示定制加工，以及精心的组装和密封。以前的研究已经用3D软光刻造影生成使用流聚集物理双乳液，但这些设备生产的乳剂，直径>150μm的9,10，要比一般分拣用FACS较大的物体大约一个数量级。一个有吸引力的替代方案将包括强大的功能的玻璃毛细管同轴流量和小液滴产生聚焦与易于制造的硅橡胶软光刻技术。在本文中，我们描述了使用同轴流动聚焦以产生≤50μm的乳剂和完全使用三维软光刻11构成的双乳液生成器。我们的设备采用了翻盖的方法来制造的设备，其中包括一个小剪切通道（图1）来近似所述乳液形成过程中拉玻璃毛细管喷嘴。更重要的是，这些设备不需要特定的表面处理，并且所有的聚合物结构提供简单和可重复的制造SCalable到大量的重复装置。在这里，我们概述了设计，制造和测试的双乳液生成器。双乳液生成被证明是健壮的，可重复至14微米的微滴直径。功能轻松制作的耦合使得该器件一个有吸引力的选项，新的双乳液的应用开发。
Protocol
Representative Results
Discussion
这里所描述的双乳液生成几何形状设计模仿的玻璃毛细管装置8的物理过程。在这些，对齐圆筒形玻璃毛细管用于创建被剪切成均匀的双乳液液滴三相同轴射流。我们的3D PDMS装置的功能是依赖于用50微米高的制造具有载波相位通道是320微米的总高度形成小的特征的中心对准。有一个显著潜力以错开的第二层掩模，在步骤1.7图案相对于50μm的高大几何的高功能，如果掩模不能准确地对…
Disclosures
The authors have nothing to disclose.
Acknowledgements
这项工作是由研究奖由美国加州理工学院定量生物科学（QB3），在缩小差距奖由罗杰斯家族基金会，加州大学旧金山分校/桑德勒基金会计划为突破生物医学研究，从巴斯夫赠款和美国国家科学基金会通过支持学院早期职业发展（CAREER）计划（DBI-1253293）。
Materials
| Photomasks | CadArt Servcies | ||
| 3" silicon wafers, P type, virgin test grade | University Wafers | 447 | |
| SU-8 3035 | Microchem | Y311074 | |
| SU-8 2050 | Microchem | Y111072 | |
| Sylgard 184 silicone elastomer kit | Krayden | 4019862 | |
| 1 ml syringes | BD | 309628 | |
| 10 ml syringes | BD | 309604 | |
| 27 gaugue needles | BD | 305109 | |
| PE 2 polyethylene tubing | Scientific Commodities, Inc. | B31695-PE/2 | |
| Novec 7500 | Fisher Scientific | 98-0212-2928-5 | Commonly knowns as HFE 7500 |
| Biocompatable surfactant | Ran Biotechnologies | 008-FluoroSurfactant | |
| 35,000 MW PEG | Sigma Aldrich | 1546660 | |
| Tween 20 | Sigma Aldrich | P1369 | |
| Sodium dodecyl sulfate | Sigma Aldrich | L3771 |
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