ISSN   1004-0595

CN  62-1095/O4

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张亚锋, 张学仁, 顾兴士, 齐慧敏, 余家欣. 微液滴/注液界面摩擦力的主/被动控制及其机理研究[J]. 摩擦学学报, 2023, 43(9): 1063-1071. doi: 10.16078/j.tribology.2022109
引用本文: 张亚锋, 张学仁, 顾兴士, 齐慧敏, 余家欣. 微液滴/注液界面摩擦力的主/被动控制及其机理研究[J]. 摩擦学学报, 2023, 43(9): 1063-1071. doi: 10.16078/j.tribology.2022109
ZHANG Yafeng, ZHANG Xueren, GU Xingshi, QI Huimin, YU Jiaxin. Active/Passive Control Method and Mechanisms for Droplet/Liquid-Infused Surface Friction[J]. TRIBOLOGY, 2023, 43(9): 1063-1071. doi: 10.16078/j.tribology.2022109
Citation: ZHANG Yafeng, ZHANG Xueren, GU Xingshi, QI Huimin, YU Jiaxin. Active/Passive Control Method and Mechanisms for Droplet/Liquid-Infused Surface Friction[J]. TRIBOLOGY, 2023, 43(9): 1063-1071. doi: 10.16078/j.tribology.2022109

微液滴/注液界面摩擦力的主/被动控制及其机理研究

Active/Passive Control Method and Mechanisms for Droplet/Liquid-Infused Surface Friction

  • 摘要: 通过结合主/被动方式控制微液滴/注液表面的摩擦力,并研究了界面摩擦力的变化机理. 结果表明:当注入流体二甲基硅油黏度从10 mm2/s增至100 mm2/s时,界面摩擦力从约15 μN增至40 μN;当外加电压从0 V增至240 V,摩擦力可以从15 μN增至45 μN左右;当外加电压从240 V逐渐降至0 V,摩擦力可以从45 μN降至15 μN左右,摩擦力实现了3倍范围内的动态调节. 分析表明,增加注液表面二甲基硅油黏度会增强微液滴/注液界面氢键作用,导致摩擦力增加. 在电压作用下,微液滴/注液表面发生介质上电润湿行为,有效界面张力随电压发生改变,实现固液界面摩擦力的动态调节. 因此,通过改变黏度的被动方式和电压控制的主动方式可以有效调节微液滴/注液表面的摩擦力,研究成果可为微流体控制系统微通道表面的优化设计及微液滴的精确输送提供技术和理论指导.

     

    Abstract:
    Microfluidic system is integrational analytical laboratory on a micro-chip to realize the generation, transportation, merging and separation of micro-droplets on the microscopic scale. Microchannels are the core parts of the microfluidic system, and the manipulation of microdroplets is mainly completed in microchannels. Consequently, the interface of microdroplet/microchannel is the mainly contact interface and the solid/liquid interface behaviors will influence the precise actuation of microdroplets. Solid/liquid interfacial friction force is an important parameter of interfacial behavior when microdroplets are transported in microchannels. Therefore, the solid/liquid interfacial behaviors can be effectively adjusted to achieve precise driving of micro-droplets by controlling and optimizing the solid/liquid interfacial friction force. The interfacial friction force can be modified by passive and active control. Generally, modifying the interfacial friction by permanently changing the morphology, structure, or surface energy of a solid surface through physical and chemical methods is a passive control. Moreover, changing the interfacial friction by external energy, such as light, electricity, magnetism et al. is an active control. However, these active control methods are limited by practical applications due to the long response time of interface to external energy. Therefore, it is necessary to explore new active control methods with fast response and wide adjustment range in order to further optimize the function of the microfluidic control system.
    In this paper, liquid-infused surfaces were prepared to study the interfacial friction behaviors. The friction force at droplet/liquid-infused surface was adjusted by adjusting the infused fluid viscosity and applied voltage. Moreover, the mechanisms of the interfacial friction force caused by fluid viscosity and applied voltage were studied. Results showed that interfacial friction force increased from about 15 to 40 μN as the infused liquid viscosity increased from 10 to 100 mm2/s. Moreover, the friction force increased from 15 μN to approximately 45 μN when the applied voltage increased from 0 V to 240 V. However, the friction force decreased from 45 μN to 15 μN when the applied voltage was gradually reduced from 240 V to 0 V. Results indicated that the friction force could be dynamically adjusted within a range of 3 times. It was deduced that the variation of friction with fluid viscosity was associated with the enhancement of the hydrogen bonding at the droplet/liquid-infused surface. Furthermore, droplet/liquid-infused surface could be considered as electrowetting system under applied voltage. The effective interfacial tension at droplet/liquid-infused interface varied with voltage, realizing the friction force dynamic adjustment. Therefore, the frictional force at droplet/liquid-infused interface could be effectively adjusted by liquid viscosity and applied voltage. The results might be helpful for providing technical and theoretical guidance to optimal microchannel design and accurately delivering microdroplet.

     

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