Hong Hyeonji, Song Jae Min, Yeom Eunseop
School of Mechanical Engineering, Pusan National University, Busan, South Korea.
Department of Oral and Maxillofacial Surgery, School of Dentistry, Pusan National University, Yangsan, South Korea.
Sci Rep. 2022 May 28;12(1):8986. doi: 10.1038/s41598-022-13165-6.
The formation of droplets or bubbles in a microfluidic system is a significant topic requiring device miniaturization and a small volume of samples. Especially, a two-phase segmented flow can be applied to micro-mixing for chemical reactions and the treatment of heat and mass transfer. In this study, a flow of liquid slugs and bubbles was generated in a 3D-printed chip and controlled by a single pump creating a vacuum at the outlet. The pump and chip device were integrated to form a simple and portable system. The size and flow rate of liquid slugs, obtained through image processing techniques, were analyzed considering several parameters related to hydraulic resistance and pressure drop. In addition, the effect of segmentation on mixing was observed by measuring the intensity change using two different colored inks. The hydraulic resistance of air and liquid flows can be controlled by changing the tube length of air flow and the viscosity of liquid flow. Because the total pressure drop along the channel was produced using a single pump at the outlet of the channel, the size and flow rate of the liquid slugs showed a near linear relation depending on the hydraulic resistances. In contrast, as the total pressure varied with the flow rate of the pump, the size of the liquid slugs showed a nonlinear trend. This indicates that the frequency of the liquid slug formation induced by the squeezed bubble may be affected by several forces during the development of the liquid slugs and bubbles. In addition, each volume of liquid slug segmented by the air is within the range of 10 to 2 µL for this microfluidic system. The segmentation contributes to mixing efficiency based on the increased homogeneity factor of liquid. This study provides a new insight to better understand the liquid slug or droplet formation and predict the segmented flow based on the relationship between the resistance, flow rate, and pressure drop.
在微流控系统中形成液滴或气泡是一个重要课题，需要设备小型化和少量样品。特别是，两相分段流可应用于化学反应的微混合以及传热传质处理。在本研究中，在3D打印芯片中产生了液塞和气泡流，并由一个在出口处产生真空的单泵进行控制。泵和芯片装置集成在一起，形成了一个简单便携的系统。通过图像处理技术获得的液塞尺寸和流速，在考虑了与水力阻力和压降相关的几个参数后进行了分析。此外，通过使用两种不同颜色的墨水测量强度变化，观察了分段对混合的影响。空气和液体流的水力阻力可以通过改变空气流的管长和液体流的粘度来控制。由于沿通道的总压降是由通道出口处的单个泵产生的，液塞的尺寸和流速根据水力阻力呈现出近似线性关系。相比之下，随着总压力随泵的流速变化，液塞的尺寸呈现出非线性趋势。这表明在液塞和气泡形成过程中，挤压气泡诱导的液塞形成频率可能受到多种力的影响。此外，对于这个微流控系统，被空气分段的每个液塞体积在10至2微升范围内。基于液体均匀性因子的增加，分段有助于提高混合效率。本研究为更好地理解液塞或液滴形成以及基于阻力、流速和压降之间的关系预测分段流提供了新的见解。
