Guan Yin, Tu Jiyue, Li Baiyun, Fu Jingwei, Zhu Mengnan, Chen Xiyang, Zhou Cheng
School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074, People's Republic of China.
School of Business Administration, Hubei University of Economics, Wuhan, Hubei 430205, People's Republic of China.
Langmuir. 2020 Aug 18;36(32):9540-9550. doi: 10.1021/acs.langmuir.0c01543. Epub 2020 Aug 3.
Microdrop generation with excellent controllability and volume precision is of paramount significance for a large variety of microfluidic applications. In this work, we propose a new configuration comprising only stripped electrodes of rectangular shape for the closed electrowetting-on-dielectric digital microfluidic (EWOD DMF) system and investigate its parallel microdrop generation outcomes via a numerical approach. The microfluidic droplet motion is solved by a finite-volume scheme on a fixed computational domain. The numerical model is verified by an experimental study of microdrop production from an EWOD DMF device with three different electrode designs. After model verification, we examine the influences of the equilibrium contact angle and the spacing of the microchannel on stripped electrode based microdrop generation outcomes and discover five different regimes including the phenomena of satellite droplet formation and separation cessation. Despite the various generation outcomes, the daughter droplet size is found to vary linearly with a dimensionless EWOD parameter κ*. More importantly, for all successful generations, the deviation of the daughter droplet size from that of the stripped electrode is smaller than 3.5%, which even reaches zero in proper conditions. This new configuration can be utilized as a convenient alternative for electrowetting-induced parallel microdrop production with excellent precision and controllability.
对于各种各样的微流体应用而言，生成具有出色可控性和体积精度的微滴至关重要。在这项工作中，我们为封闭式介电电润湿数字微流控（EWOD DMF）系统提出了一种仅由矩形剥离电极组成的新配置，并通过数值方法研究其并行微滴生成结果。微流体液滴运动通过固定计算域上的有限体积格式求解。通过对具有三种不同电极设计的EWOD DMF装置产生微滴的实验研究验证了数值模型。模型验证后，我们研究了平衡接触角和微通道间距对基于剥离电极的微滴生成结果的影响，并发现了五种不同状态，包括卫星液滴形成和分离停止现象。尽管有各种生成结果，但发现子液滴尺寸与无量纲EWOD参数κ*呈线性变化。更重要的是，对于所有成功的生成，子液滴尺寸与剥离电极尺寸的偏差小于3.5%，在适当条件下甚至达到零。这种新配置可作为一种方便的替代方案，用于以优异的精度和可控性通过电润湿诱导并行生成微滴。
