Peng Cheng-Yun, Tsai Chia-Hung Dylan
Department of Mechanical Engineering, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan.
Polymers (Basel). 2021 Apr 17;13(8):1321. doi: 10.3390/polym13081321.
Droplet manipulation is important in the fields of engineering, biology, chemistry, and medicine. Many techniques, such as electrowetting and magnetic actuation, have been developed for droplet manipulation. However, the fabrication of the manipulation platform often takes a long time and requires well-trained skills. Here we proposed a novel method that can directly generate and manipulate droplets on a polymeric surface using a universal plasma jet. One of its greatest advantages is that the jet can tremendously reduce the time for the platform fabrication while it can still perform stable droplet manipulation with controllable droplet size and motion. There are two steps for the proposed method. First, the universal plasma jet is set in plasma mode for modifying the manipulation path for droplets. Second, the jet is switched to air-jet mode for droplet generation and manipulation. The jetted air separates and pushes droplets along the plasma-treated path for droplet generation and manipulation. According to the experimental results, the size of the droplet can be controlled by the treatment time in the first step, i.e., a shorter treatment time of plasma results in a smaller size of the droplet, and vice versa. The largest and the smallest sizes of the generated droplets in the results are about 6 µL and 0.1 µL, respectively. Infrared spectra of absorption on the PDMS surfaces with and without the plasma treatment are investigated by Fourier-transform infrared spectroscopy. Tests of generating and mixing two droplets on a PDMS surface are successfully achieved. The aging effect of plasma treatment for the proposed method is also discussed. The proposed method provides a simple, fast, and low-cost way to generate and manipulate droplets on a polymeric surface. The method is expected to be applied to droplet-based cell culture by manipulating droplets encapsulating living cells and towards wall-less scaffolds on a polymeric surface.
液滴操控在工程、生物学、化学和医学领域都很重要。人们已经开发出许多技术，如电润湿和磁驱动，用于液滴操控。然而，操控平台的制造通常需要很长时间，并且需要训练有素的技能。在此，我们提出了一种新颖的方法，即使用通用等离子体射流在聚合物表面直接生成和操控液滴。其最大的优点之一是，该射流可以极大地缩短平台制造时间，同时仍能以可控的液滴大小和运动进行稳定的液滴操控。所提出的方法有两个步骤。首先，将通用等离子体射流设置为等离子体模式，以修改液滴的操控路径。其次，将射流切换到空气射流模式以生成和操控液滴。喷射的空气将液滴分离并沿等离子体处理过的路径推动液滴，以进行液滴的生成和操控。根据实验结果，液滴的大小可以通过第一步中的处理时间来控制，即等离子体处理时间越短，液滴尺寸越小，反之亦然。结果中生成的液滴的最大和最小尺寸分别约为6微升和0.1微升。通过傅里叶变换红外光谱研究了有无等离子体处理的聚二甲基硅氧烷（PDMS）表面的红外吸收光谱。成功实现了在PDMS表面生成和混合两个液滴的测试。还讨论了所提出方法中等离子体处理的老化效应。所提出的方法提供了一种在聚合物表面生成和操控液滴的简单、快速且低成本的方法。该方法有望通过操控包裹活细胞的液滴应用于基于液滴的细胞培养，并应用于聚合物表面的无壁支架。
