以减少液滴表面的相互作用来优化Bioanalytes运输中的数字微流体
Summary
The protocol for fabrication and operation of field dewetting devices (Field-DW) is described, as well as the preliminary studies of the effects of electric fields on droplet contents.
Abstract
Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of “lab-on-a-chip” platforms. Often, droplet motion relies on the wetting of a surface, directly associated with the application of an electric field; surface interactions, however, make motion dependent on droplet contents, limiting the breadth of applications of the technique.
Some alternatives have been presented to minimize this dependence. However, they rely on the addition of extra chemical species to the droplet or its surroundings, which could potentially interact with droplet moieties. Addressing this challenge, our group recently developed Field-DW devices to allow the transport of cells and proteins in DMF, without extra additives.
Here, the protocol for device fabrication and operation is provided, including the electronic interface for motion control. We also continue the studies with the devices, showing that multicellular, relatively large, model organisms can also be transported, arguably unaffected by the electric fields required for device operation.
Introduction
该液体的工作装置的小型化是非常重要的用于“芯片实验室”的平台的开发。在这个方向上，在过去二十年已经见证了在微流体领域的显著进展，具有各种应用。1-5用流体在封闭的通道（通道微流）的传输对比，DMF操纵上的电极阵列的微滴。其中，最有吸引力的这种技术的优点是没有可动部件运送流体，并且运动是通过关闭电信号即刻停止。
然而，雾滴的运动依赖于液滴内容，当然对于通用的“芯片实验室”的平台不希望的特性。含有蛋白质和其它分析物的微滴粘到设备的表面，成为不可移动。可以说，这一直是主要的限制为拓宽DMF的应用范围; 6-8替代方案，以尽量减少不希望的表面结垢涉及添加额外的化学物质，以液滴或它的周围，这有可能影响液滴的内容。
先前，我们小组开发出一种装置，以允许细胞和蛋白质在DMF中的传输，而无需额外的添加剂（现场DW的设备）。9这是通过基于蜡烛烟灰，10与设备的几何形状有利于液滴滚动表面相结合来实现并导致在熔滴上的向上的力，从而进一步降低液滴的表面相互作用。在这种方法中，液滴运动并不与表面润湿相关联。11
下面描述的详细方法的目标是产生一个微流体装置能够输送含有蛋白质，细胞和整个生物体的液滴，而无需额外的添加剂。在现场-DW设备铺平了道路液滴工作的化学家很大程度上独立完全控制平台RY。
在这里，我们还存在模拟表明，尽管所需的设备的操作的高电压，在整个液滴上的电压降是所施加的电压的一小部分，这表明在液滴内部bioanalytes的影响可以忽略。事实上，与秀丽隐杆线虫 （ 线虫 ），用于各种生物学研究线虫的初步试验，表明蠕虫游泳原状作为施加电压。
Protocol
Representative Results
Discussion
该协议中最关键的步骤是保护的烟灰层的，可直接与在移动液滴的成功相关联。金属化的烟灰层（上述的方法1）允许接近制造成功的100％。然而，最大的操作时间约为10分钟;可能的话，微滴级分通过在所述金属层的孔润湿烟灰。涂烟灰层的氟化液是最简单和最快的替代，需要最少的资源，但只有40％-50％的基板制作工作（20分最高）的 – 和涂层不均匀。实际上，该烟灰层是非常脆弱的，而且在粘?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
我们感谢Lindback基金会的资金支持，而亚历山大西多连科医 生和埃尔萨楚的富有成果的讨论和技术援助，以及罗伯特·史密斯教授的协助C.线虫检测。
Materials
| Name of Material/ Equipment | Company | Catalog Number | Comments/Description |
| Paraffin candle | Any paraffin candle | ||
| Sputtering system | Denton Vacuum, Moorestown, NJ | Sputter coater Desk V HP equipped with an Au target. | |
| 1-dodecanethiol | Sigma-Aldrich | 471364 | |
| Teflon | Dupont | AF-1600 | |
| Fluorinert FC-40 | Sigma-Aldrich | F9755 | Fluorinated liquid: Prepare Teflon-AF resin in Fluorinert FC-40, 1:100 (w/w), to create the hydrophobic coating. |
| Graphic design software -Adobe Illustrator | Adobe Systems | Other softwares might be used as well. | |
| Copper laminate | Dupont | LF9110 | |
| Laser Printer | Xerox | Phaser 6360 or similar | Check for the compatibility with "rich black" or "registration black" (see text). |
| Copper Etchant | Transene | CE-100 | |
| Perfluoroalkoxy (PFA) film | McMaster-Carr | 84955K22 | |
| Breadboard | Allied Electronics | 70012450 or similar | Large enough to allow the assemble of 10 drivers. |
| Universal circuit board | Allied Electronics | 70219535 or similar | |
| Connector | Allied Electronics | 5145154-8 or similar | |
| Control board and control program (LabView software) | National Instruments | NI-6229 or similar | |
| High-voltage amplifier | Trek | PZD700 | |
| Resistor R 27 kΩ, 1/4 W | Allied | 2964762 | |
| Capacitors C and C1, 100 nF, 60 V | Allied | 8817183 | |
| Transistor T, NPN | Allied | 9350289 | |
| Diode D, 1N4007 | Allied | 2660007 | |
| Relay | Allied | 8862527 | |
| Visualization system | Edmund Optics | VZM 200i or similar | System magnification 24X- 96X. It is combined with a Hitachi KP-D20B 1/2 in CCD Color Camera. |
| Recorder | Sony | GV-D1000 NTSC or similar | It is connected to the camera by an S-video cable. |
| Simulations | COMSOL Multiphysics | V. 4.4 |
References
- Fair, R. B. Digital microfluidics: is a true lab-on-a-chip possible. Microfluid Nanofluid. 3 (3), 245-281 (2007).
- Gupta, S., Alargova, R. G., Kilpatrick, P. K., Velev, O. D. On-Chip Dielectrophoretic Coassembly of Live Cells and Particles into Responsive Biomaterials. Langmuir. 26 (5), 3441-3452 (2009).
- Shih, S. C., et al. Dried blood spot analysis by digital microfluidics coupled to nanoelectrospray ionization mass spectrometry. Anal Chem. 84 (8), 3731-3738 (2012).
- Gorbatsova, J., Borissova, M., Kaljurand, M. Electrowetting-on-dielectric actuation of droplets with capillary electrophoretic zones for off-line mass spectrometric analysis. J Chromatogr. 1234, 9-15 (2012).
- Qin, J., Wheeler, A. R. Maze exploration and learning in C. elegans. Lab Chip. 7 (2), 186-192 (2007).
- Koc, Y., de Mello, A. J., McHale, G., Newton, M. I., Roach, P., Shirtcliffe, N. J. Nano-scale superhydrophobicity: suppression of protein adsorption and promotion of flow-induced detachment. Lab Chip. 8 (4), 582-586 (2008).
- Perry, G., Thomy, V., Das, M. R., Coffinier, Y., Boukherroub, R. Inhibiting protein biofouling using graphene oxide in droplet-based microfluidic microsystems. Lab Chip. 12 (9), 1601-1604 (2012).
- Kumari, N., Garimella, S. V. Electrowetting-Induced Dewetting Transitions on Superhydrophobic Surfaces. Langmuir. 27 (17), 10342-10346 (2011).
- Freire, S. L. S., Tanner, B. Additive-Free Digital Microfluidics. Langmuir. 29 (28), 9024-9030 (2013).
- Deng, X., Mammen, L., Butt, H. -. J., Vollmer, D. Candle Soot as a Template for a Transparent Robust Superamphiphobic Coating. Science. 335, 67-70 (2011).
- Kang, K. H. How Electrostatic Fields Change Contact Angle in Electrowetting. Langmuir. 18 (26), 10318-10322 (2002).
- Abdelgawad, M., Watson, M. W. L., Young, E. W. K., Mudrik, J. M., Ungrin, M. D., Wheeler, A. R. Soft lithography: masters on demand. Lab Chip. 8 (8), 1379-1385 (2008).
- Barbulovic-Nad, I., Yang, H., Park, P. S., Wheeler, A. R. Digital microfluidics for cell-based assays. Lab Chip. 8 (4), 519-526 (2008).
- Brenner, S. The genetics of Caenorhabditis elegans. 유전학. 77 (1), 71-94 (1974).
