Department of Mechanical Engineering and Materials Science, University of Pittsburgh, PA 15261, USA.
Department of Civil and Environmental Engineering, University of Pittsburgh, PA 15261, USA.
Lab Chip. 2017 Mar 14;17(6):1060-1068. doi: 10.1039/c7lc00006e.
Generating, splitting, transporting, and merging droplets are fundamental and critical unit operations for digital (droplet-based) microfluidics. State-of-the-art digital microfluidics performs such operations commonly using electrowetting-on-dielectric (EWOD) in the typical configuration of two parallel channel plates. This paper presents such operations using dielectrowetting (derived from liquid dielectrophoresis), not EWOD, with an array of interdigitated electrodes. The major and unique feature is that the present droplet manipulations are effective for conductive (water with/without surfactant) and non-conductive (propylene carbonate) fluids. An equally important aspect is that the manipulations are performed in an open space without the covering top plate. This behavior is attributed to the intrinsic nature of dielectrowetting to generate stronger wetting forces than EWOD (with the ability to achieve complete wetting with contact angle = 0° to form a thin film). Using dielectrowetting, micro-droplets of various volumes are created from a large droplet and transported. Splitting a single droplet as well as multiple droplets and merging them are also achieved, even when the droplets are smaller than the electrode pads. The above splitting, transport, and merging operations are effective for propylene carbonate as well as DI water with/without surfactant, though the creating operation is proven only for propylene carbonate at this moment. All the above manipulations are successfully carried out on a single plate, which not only simplifies the structure and operation procedure, but could also eliminate the restriction to the volume of fluid handled.
生成、分裂、输送和合并液滴是数字（液滴式）微流控的基本和关键单元操作。最先进的数字微流控通常使用两个平行通道板的典型配置中的介电润湿（电润湿）来执行此类操作。本文使用叉指电极阵列演示了使用介电泳（源自液体电介质电泳）而不是电润湿的此类操作。主要且独特的特点是，目前的液滴操作对于导电（含/不含表面活性剂的水）和非导电（碳酸丙烯酯）流体均有效。同样重要的方面是，操作是在没有覆盖顶板的开放空间中进行的。这种行为归因于介电泳产生比电润湿更强的润湿力的固有性质（能够实现接触角为 0°的完全润湿以形成薄膜）。使用介电泳，可以从小型液滴中创建各种体积的微液滴并进行输送。即使液滴小于电极垫，也可以实现单个液滴的分裂以及多个液滴的分裂和合并。上述分裂、输送和合并操作对于碳酸丙烯酯以及含/不含表面活性剂的去离子水均有效，尽管目前仅证明了用于碳酸丙烯酯的创建操作。所有上述操作都可以在单个板上成功执行，这不仅简化了结构和操作程序，而且还可以消除对处理流体体积的限制。
