| ZHANG Xue-ren,ZHANG Ya-feng,GU Xing-shi,YU Jia-xin.Active/Passive Control and Mechanism of the Adhesion Behaviors of Droplet/Liquid-infused Surface[J],52(10):304-312 |
| Active/Passive Control and Mechanism of the Adhesion Behaviors of Droplet/Liquid-infused Surface |
| Received:October 13, 2022 Revised:January 17, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.10.026 |
| KeyWord:microdroplet liquid-infused surface adhesion electrowetting interface adjustment |
| Author | Institution |
| ZHANG Xue-ren |
Key Laboratory of Testing Technology for Manufacturing Process, Ministry of Education, Southwest University of Science and Technology, Sichuan Mianyang , China |
| ZHANG Ya-feng |
Key Laboratory of Testing Technology for Manufacturing Process, Ministry of Education, Southwest University of Science and Technology, Sichuan Mianyang , China |
| GU Xing-shi |
Key Laboratory of Icing and Anti/De-icing, China Aerodynamics Research and Development Center, Sichuan Mianyang , China |
| YU Jia-xin |
Key Laboratory of Testing Technology for Manufacturing Process, Ministry of Education, Southwest University of Science and Technology, Sichuan Mianyang , China |
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| Abstract: |
| Controlling microdroplets has gotten wide attention due to its potential applications in drug delivery, microfluidic devices and lab on chip, etc. Recently, various methods were used to manipulate microdroplet. For example, surfaces were modified by coating with different surface energy, or by micro-structures to change the property of surface to manipulate microdroplet. These methods were classified as passive methods because the functions of the surface could not be changed when the surface was modified. Moreover, active methods, such as temperature, light, electricity, magnetism and mechanical stress, etc. were used to manipulate microdroplet dynamically. However, although the adhesion behavior at liquid/solid interface could be adjusted, some obstacles such as long response time, high energy consumption and droplet pollution, limited the application of those technologies. Therefore, a combined active and passive approach was required to manipulate microdroplets with fast response time, low energy consumption, and no pollution. In this study, silicon chip with size of 20 mm×20 mm was used as substrate. To ensure the conductivity, the back of the silicon chip was ground with sandpaper to remove the oxide layer. Then, the silicon chip was coated by spraying superhydrophobic liquid. After drying for 1 h, the superhydrophobic film was formed. The liquid-infused surfaces were prepared by adding lubricating oil (polydimethylsiloxane) to the superhydrophobic surface. Droplet was placed on the oil-infused surface and then electrowetting system on the droplet/oil-infused surface was established with applied voltage. Lubricant with viscosity of 10 mm2/s, 50 mm2/s and 100 mm2/s and applied voltage (0-240 V) were used in this work. Moreover, the effect of oil viscosity and applied voltage on the droplet/oil-infused surface adhesion behaviors was investigated. The adhesion mechanisms under the coupling effects of lubricating oil viscosity and applied voltage were studied. The adhesion force variation process could be described with snap-in force, maximum force and pull-off force. The snap-in force decreased from 194 μN to 123 μN, the maximum force decreased from 129 μN to 94 μN, and the pull-off force decreased from 101 μN to 82 μN when the liquid viscosity increased from 10 mm2/s to 100 mm2/s. Snap-in force increased from 156 μN to 322 μN, the maximum force increased from 120 μN to 178 μN and the pull-off force decreased from 85 μN to 53 μN when the applied voltage increased from 0 V to 240 V. Active control of the adhesion behaviors is achieved. It is indicated that the high-viscosity polydimethylsiloxane has strong internal shear force, however, the long chain will enhance the hydrogen at the droplet/liquid-infused surface. Consequently, the snap-in force, the maximum force and the pull-off force decrease with viscosity. Moreover, the effective interface energy varies nonlinearly with the voltage, realizing real-time adjustment of the adhesion force of the droplet/liquid-infused surface. The adhesion behaviors of droplet/liquid-infused surface can be actively/passively controlled by changing the voltage and the viscosity of the lubricant. Results help to provide theoretical and technical guidance for development of a new micro-droplet controlling method. |
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