Zhou Yidi, Liu Jixiao, Yan Junjia, Zhu Tong, Guo Shijie, Li Songjing, Li Tiejun
School of Mechanical Engineering, Hebei University of Technology, Tianjin 300132, China.
Hebei Key Laboratory of Robot Perception and Human-Robot Interaction, Hebei University of Technology, Tianjin 300401, China.
Micromachines (Basel). 2020 Apr 10;11(4):396. doi: 10.3390/mi11040396.
Unstable liquid flow in syringe pump-driven systems due to the low-speed vibration of the step motor is commonly observed as an unfavorable phenomenon, especially when the flow rate is relatively small. Upon the design of a convenient and cost-efficient microfluidic standing air bubble system, this paper studies the physical principles behind the flow stabilization phenomenon of the bubble-based hydraulic capacitors. A bubble-based hydraulic capacitor consists of three parts: tunable microfluidic standing air bubbles in specially designed crevices on the fluidic channel wall, a proximal pneumatic channel, and porous barriers between them. Micro-bubbles formed in the crevices during liquid flow and the volume of the bubble can be actively controlled by the pneumatic pressure changing in the proximal channel. When there is a flowrate fluctuation from the upstream, the flexible air-liquid interface would deform under the pressure variation, which is analogous to the capacitive charging/discharging process. The theoretical model based on Euler law and the microfluidic equivalent circuit was developed to understand the multiphysical phenomenon. Experimental data characterize the liquid flow stabilization performance of the flow stabilizer with multiple key parameters, such as the number and the size of microbubbles. The developed bubble-based hydraulic capacitor could minimize the flow pulses from syringe pumping by 75.3%. Furthermore, a portable system is demonstrated and compared with a commercial pressure-driven flow system. This study can enhance the understanding of the bubble-based hydraulic capacitors that would be beneficial in microfluidic systems where the precise and stable liquid flow is required.
由于步进电机的低速振动，在注射泵驱动系统中普遍观察到不稳定的液体流动，这是一种不利现象，尤其是当流速相对较小时。在设计一种方便且经济高效的微流控驻气泡系统时，本文研究了基于气泡的液压电容器流动稳定现象背后的物理原理。基于气泡的液压电容器由三部分组成：在流体通道壁上专门设计的缝隙中的可调谐微流控驻气泡、近端气动通道以及它们之间的多孔屏障。液体流动过程中在缝隙中形成的微气泡以及气泡的体积可以通过近端通道中气压的变化来主动控制。当上游存在流速波动时，柔性气液界面会在压力变化下变形，这类似于电容的充电/放电过程。基于欧拉定律和微流控等效电路建立了理论模型，以理解这种多物理现象。实验数据用多个关键参数表征了流动稳定器的液体流动稳定性能，如微气泡的数量和大小。所开发的基于气泡的液压电容器可将注射泵产生的流动脉冲最小化75.3%。此外，展示了一个便携式系统，并与商业压力驱动流动系统进行了比较。这项研究可以增进对基于气泡的液压电容器的理解，这将有利于需要精确和稳定液体流动的微流控系统。
