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Limin He - One of the best experts on this subject based on the ideXlab platform.
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electrocoalescence criterion of conducting Droplets suspended in a viscous fluid
Journal of Physical Chemistry C, 2019Co-Authors: Yuling Lu, Limin HeAbstract:Coalescence of conducting Droplets dispersed in an immiscible medium can be facilitated by an electric field. However, Droplets recoil promptly after contact in sufficiently high electric fields if the cone angle between Droplets exceeds a critical value. To elucidate the critical condition for Droplet coalescence, the behavior of two suspended Droplets after contact with a direct current electric field is studied. It is shown that the critical angle is determined not only by the Droplet geometry but also conductivity, surfactant concentration, and size. As the Droplet conductivity increases, more identical ions accumulate on the adjacent interfaces of two Droplets due to the faster ionic migration, which results in Coulombic repulsion between Droplets and a reduced critical angle. For surfactant-laden Droplets, film drainage induces a surfactant concentration gradient on the leading edges of Droplets, and then Marangoni stress is formed to reduce the critical angle. In the case of large Droplets, the bri...
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electrocoalescence criterion of conducting Droplets suspended in a viscous fluid
The Journal of Physical Chemistry, 2019Co-Authors: Yuling Lu, Limin HeAbstract:Coalescence of conducting Droplets dispersed in an immiscible medium can be facilitated by an electric field. However, Droplets recoil promptly after contact in sufficiently high electric fields if the cone angle between Droplets exceeds a critical value. To elucidate the critical condition for Droplet coalescence, the behavior of two suspended Droplets after contact with a direct current electric field is studied. It is shown that the critical angle is determined not only by the Droplet geometry but also conductivity, surfactant concentration, and size. As the Droplet conductivity increases, more identical ions accumulate on the adjacent interfaces of two Droplets due to the faster ionic migration, which results in Coulombic repulsion between Droplets and a reduced critical angle. For surfactant-laden Droplets, film drainage induces a surfactant concentration gradient on the leading edges of Droplets, and then Marangoni stress is formed to reduce the critical angle. In the case of large Droplets, the bridge transiently expands under the action of directional flow caused by further Droplet deformation, but eventually breaks due to opposite electrostatic forces. Based on this finding, the electrocoalescence criterion can be determined and employed to facilitate Droplet coalescence in various applications.
Yuling Lu - One of the best experts on this subject based on the ideXlab platform.
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electrocoalescence criterion of conducting Droplets suspended in a viscous fluid
Journal of Physical Chemistry C, 2019Co-Authors: Yuling Lu, Limin HeAbstract:Coalescence of conducting Droplets dispersed in an immiscible medium can be facilitated by an electric field. However, Droplets recoil promptly after contact in sufficiently high electric fields if the cone angle between Droplets exceeds a critical value. To elucidate the critical condition for Droplet coalescence, the behavior of two suspended Droplets after contact with a direct current electric field is studied. It is shown that the critical angle is determined not only by the Droplet geometry but also conductivity, surfactant concentration, and size. As the Droplet conductivity increases, more identical ions accumulate on the adjacent interfaces of two Droplets due to the faster ionic migration, which results in Coulombic repulsion between Droplets and a reduced critical angle. For surfactant-laden Droplets, film drainage induces a surfactant concentration gradient on the leading edges of Droplets, and then Marangoni stress is formed to reduce the critical angle. In the case of large Droplets, the bri...
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electrocoalescence criterion of conducting Droplets suspended in a viscous fluid
The Journal of Physical Chemistry, 2019Co-Authors: Yuling Lu, Limin HeAbstract:Coalescence of conducting Droplets dispersed in an immiscible medium can be facilitated by an electric field. However, Droplets recoil promptly after contact in sufficiently high electric fields if the cone angle between Droplets exceeds a critical value. To elucidate the critical condition for Droplet coalescence, the behavior of two suspended Droplets after contact with a direct current electric field is studied. It is shown that the critical angle is determined not only by the Droplet geometry but also conductivity, surfactant concentration, and size. As the Droplet conductivity increases, more identical ions accumulate on the adjacent interfaces of two Droplets due to the faster ionic migration, which results in Coulombic repulsion between Droplets and a reduced critical angle. For surfactant-laden Droplets, film drainage induces a surfactant concentration gradient on the leading edges of Droplets, and then Marangoni stress is formed to reduce the critical angle. In the case of large Droplets, the bridge transiently expands under the action of directional flow caused by further Droplet deformation, but eventually breaks due to opposite electrostatic forces. Based on this finding, the electrocoalescence criterion can be determined and employed to facilitate Droplet coalescence in various applications.
Fei Peng Wang - One of the best experts on this subject based on the ideXlab platform.
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Droplet condensation on superhydrophobic surfaces with enhanced dewetting under a tangential ac electric field
Applied Physics Letters, 2016Co-Authors: Jian Li, Zheng Yong Huang, Licheng Li, Fei Peng WangAbstract:In this Letter, the dewetting behavior of superhydrophobic condensing surfaces under a tangential AC electric field is reported. The surface coverage of condensed Droplets only exhibits a negligible increase with time. The jumping frequency of Droplets is enhanced. The AC electric field motivates the dynamic transition of Droplets from stretch to recoil, resulting in the counterforce propelling Droplet jumping. The considerable horizontal component of jumping velocity facilitates Droplet departure from superhydrophobic surfaces. Both the amplitude and frequency of AC voltage are important factors for Droplet departure and dewetting effect. Thereby, the tangential electric field provides a unique and easily implementable approach to enhance Droplet removal from superhydrophobic condensing surfaces.
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the collision behavior of Droplets splitted from a Droplet that rebounded on super hydrophobic surface
Applied Mechanics and Materials, 2015Co-Authors: Zheng Yong Huang, Fei Peng Wang, Huan Huan XiaAbstract:Droplet rebounding on super-hydrophobic surfaces is critical to suppress pollution flashover (i.e. enhancement of pollution flashover-voltage) and to reduce ice accumulation on insulators. This paper presents a novel way to reduce water accumulation on surface via the elastic collision between Droplets splitted from a Droplet that has rebounded from super-hydrophobic surface. The water-mass that contacted with surface will be reduced resultantly. The influence of hydrophobicity of the surface on contact time and spreading time of water Droplets are discussed. The collision behavior between the splitted Droplets is indicated by the surface charge that was induced by the rebounding Droplets on super-hydrophobic surface. Experimental results show that the super-hydrophobic surface endows water Droplets with shorter contact time, spreading time than those values obtained on a bare glass. Specific Web and Reynolds numbers can lead to the elastic rebounding between water Droplets, delaying the water contact with the super-hydrophobic surface. The contact electrification between the rebounded Droplet and the super-hydrophobic surface renders the Droplet charged, thus determines the collision behavior of the splitted Droplets that born from the rebounded Droplet.
Zhuang Zhi Chong - One of the best experts on this subject based on the ideXlab platform.
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ac electric field induced Droplet deformation in a microfluidic t junction
Lab on a Chip, 2016Co-Authors: Hengdong Xi, Michael Leniart, Zhuang Zhi ChongAbstract:We present for the first time an experimental study on the Droplet deformation induced by an AC electric field in Droplet-based microfluidics. It is found that the deformation of the Droplets becomes stronger with increasing electric field intensity and frequency. The measured electric field intensity dependence of the Droplet deformation is consistent with an early theoretical prediction for stationary Droplets. We also proposed a simple equivalent circuit model to account for the frequency dependence of the Droplet deformation. The model well explains our experimental observations. In addition, we found that the Droplets can be deformed repeatedly by applying an amplitude modulation (AM) signal.
In Seok Kang - One of the best experts on this subject based on the ideXlab platform.
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a novel actuation method of transporting Droplets by using electrical charging of Droplet in a dielectric fluid
Biomicrofluidics, 2009Co-Authors: Yongmi Jung, In Seok KangAbstract:We evaluate the feasibility of manipulating Droplets in two dimensions by exploiting Coulombic forces acting on conductive Droplets immersed in a dielectric fluid. When a Droplet suspended in an immiscible fluid is located near an electrode under a dc voltage, the Droplet can be charged by direct contact, by charge transfer along an electrically conducting path, or by both mechanisms. This process is called electrical charging of Droplet (ECOD). This charged Droplet may then be transported rapidly by exploiting Coulombic forces. We experimentally demonstrate electrical actuation of a charged Droplet by applying voltage sequences. A charged Droplet is two dimensionally actuated by following the direction of the electrical field signal. The Droplet does not contact the surface of the microfluidic chip when it moves. This characteristic is very advantageous because treatments of the substrate surfaces of microfluidic chip become simpler. In order to test the feasibility of using ECOD in a Droplet-based microreactor, electrocoalescence of two oppositely charged Droplets is also studied. When two Droplets approach each other due to Coulombic attraction, a liquid bridge is formed between them. We postulate that if the applied electric field is weaker than a certain critical level, the two Droplets coalesce instantaneously when the charges are exchanged and redistributed through this liquid bridge.
