Universal Plasma Jet for Droplet Manipulation on a PDMS Surface towards Wall-Less Scaffolds.

Cheng-Yun Peng,Chia-Hung Dylan Tsai

doi:10.3390/polym13081321

Abstract

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.

Highlights

Droplet manipulation is an important technique for engineering, biomedical and chemical research because it drastically reduces the volume of samples and significantly improves the efficiency of the tests [1,2,3]
Um et al [19] developed a continuous generation of hydrogel beads with encapsulation of biological materials for tissue engineering
It can be interpreted as that the longer treatment time leads to a greater dose of plasma treatment on the PDMS surface, as well as wider hydrophilic path

Summary

Introduction

Droplet manipulation is an important technique for engineering, biomedical and chemical research because it drastically reduces the volume of samples and significantly improves the efficiency of the tests [1,2,3]. Zhang et al [15] developed a microfluidic-based nozzle for fabricating microspheres from high-viscosity bioink. Du et al [16] used a tapered capillary connected with a syringe pump for screening cell-based drug combination on a droplet-based microfluidic system. Biodegradable polymers can be used as scaffolds for cell cultivation [17,18]. Um et al [19] developed a continuous generation of hydrogel beads with encapsulation of biological materials for tissue engineering. Li et al [20] used aligned fibers in polyglycerol sebacate (PGS) and polyvinyl alcohol (PVA) scaffolds for directing cell alignment

Methods

Results

Discussion

Conclusion