The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Detlef Lohse - One of the best experts on this subject based on the ideXlab platform.
-
evaporating pure binary and ternary droplets thermal effects and axial symmetry breaking
Journal of Fluid Mechanics, 2017Co-Authors: Christian Diddens, Michel Versluis, Huanshu Tan, Jgm Hans Kuerten, Xuehua Zhang, Detlef LohseAbstract:The Greek aperitif Ouzo is not only famous for its specific anise-flavoured taste, but also for its ability to turn from a transparent miscible liquid to a milky-white coloured emulsion when water is added. Recently, it has been shown that this so-called Ouzo effect, i.e. the spontaneous emulsification of oil microdroplets, can also be triggered by the preferential evaporation of ethanol in an evaporating sessile Ouzo drop, leading to an amazingly rich drying process with multiple phase transitions (Tan et al., Proc. Natl Acad. Sci. USA, vol. 113 (31), 2016, pp. 8642-8647). Due to the enhanced evaporation near the contact line, the nucleation of oil droplets starts at the rim which results in an oil ring encircling the drop. Furthermore, the oil droplets are advected through the Ouzo drop by a fast solutal Marangoni Flow. In this article, we investigate the evaporation of mixture droplets in more detail, by successively increasing the mixture complexity from pure water over a binary water-ethanol mixture to the ternary Ouzo mixture (water, ethanol and anise oil). In particular, axisymmetric and full three-dimensional finite element method simulations have been performed on these droplets to discuss thermal effects and the complicated Flow in the droplet driven by an interplay of preferential evaporation, evaporative cooling and solutal and thermal Marangoni Flow. By using image analysis techniques and micro-particle-image-velocimetry measurements, we are able to compare the numerically predicted volume evolutions and velocity fields with experimental data. The Ouzo droplet is furthermore investigated by confocal microscopy. It is shown that the oil ring predominantly emerges due to coalescence.
-
evaporating pure binary and ternary droplets thermal effects and axial symmetry breaking
arXiv: Fluid Dynamics, 2017Co-Authors: Christian Diddens, Michel Versluis, Huanshu Tan, Jgm Hans Kuerten, Xuehua Zhang, Detlef LohseAbstract:The Greek aperitif Ouzo is not only famous for its specific anise-flavored taste, but also for its ability to turn from a transparent miscible liquid to a milky-white colored emulsion when water is added. Recently, it has been shown that this so-called Ouzo effect, i.e. the spontaneous emulsification of oil microdroplets, can also be triggered by the preferential evaporation of ethanol in an evaporating sessile Ouzo drop, leading to an amazingly rich drying process with multiple phase transitions [H. Tan et al., Proc. Natl. Acad. Sci. USA 113(31) (2016) 8642]. Due to the enhanced evaporation near the contact line, the nucleation of oil droplets starts at the rim which results in an oil ring encircling the drop. Furthermore, the oil droplets are advected through the Ouzo drop by a fast solutal Marangoni Flow. In this article, we investigate the evaporation of mixture droplets in more detail, by successively increasing the mixture complexity from pure water over a binary water-ethanol mixture to the ternary Ouzo mixture (water, ethanol and anise oil). In particular, axisymmetric and full three-dimensional finite element method simulations have been performed on these droplets to discuss thermal effects and the complicated Flow in the droplet driven by an interplay of preferential evaporation, evaporative cooling and solutal and thermal Marangoni Flow. By using image analysis techniques and micro-PIV measurements, we are able to compare the numerically predicted volume evolutions and velocity fields with experimental data. The Ouzo droplet is furthermore investigated by confocal microscopy. It is shown that the oil ring predominantly emerges due to coalescence.
-
Marangoni Flow on an inkjet nozzle plate
Applied Physics Letters, 2007Co-Authors: Jos De Jong, Hans Reinten, Herman Wijshoff, Marc Van Den Berg, Koos Delescen, Rini Van Dongen, Frieder Mugele, Michel Versluis, Detlef LohseAbstract:In piezo inkjet printing, nozzle failures are often caused by an ink layer on the nozzle plate. It is experimentally shown that the ink layer at the nozzle is formed through streamers of ink, emanating from a central ink band on the nozzle plate. The streamers propagate over a wetting nanofilm of 13 nm thickness, directed toward the actuated nozzles. The motion of the front end of the streamers follows a power law in time with an exponent ½. The observations are consistent with a surface tension gradient driven Flow. The origin of the Marangoni Flow is an effective lower surfactant concentration of the ink around the nozzle.
Alois Würger - One of the best experts on this subject based on the ideXlab platform.
-
thermally driven Marangoni surfers
Journal of Fluid Mechanics, 2014Co-Authors: Alois WürgerAbstract:We study autopropulsion of an interface particle that is driven by the Marangoni stress arising from a self-generated asymmetric temperature or concentration field. We calculate separately the long-range Marangoni Flow $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}{\boldsymbol {v}}^{I}$ due to the stress discontinuity at the interface and the short-range velocity field ${\boldsymbol {v}}^{P}$ imposed by the no-slip condition on the particle surface. Both contributions are evaluated for a spherical floater with temperature monopole and dipole moments. We find that the self-propulsion velocity is given by the amplitude of the ‘source doublet’ that belongs to the short-range contribution ${\boldsymbol {v}}^{P}$ . Hydrodynamic interactions, on the other hand, are determined by the long-range Marangoni Flow ${\boldsymbol {v}}^{I}$ . Its dipolar part results in an asymmetric advection pattern of neighbouring particles, which in turn may perturb the known hexatic lattice or even favour disordered states.
-
Thermally driven Marangoni surfers
Journal of Fluid Mechanics, 2014Co-Authors: Alois WürgerAbstract:We study auto-propulsion of a interface particle, which is driven by the Marangoni stress arising from a self-generated asymmetric temperature or concentration field. We calculate separately the long-range Marangoni Flow v^{I} due to the stress discontinuity at the interface and the short-range velocity field v^{P} imposed by the no-slip condition on the particle surface; both contributions are evaluated for a spherical floater with temperature monopole and dipole moments. We find that the self-propulsion velocity is given by the amplitude of the "source doublet" which belongs to short-range contribution v^{P}. Hydrodynamic interactions, on the other hand, are determined by the long-range Marangoni Flow v^{I}; its dipolar part results in an asymmetric advection pattern of neighbor particles, which in turn may perturb the known hexatic lattice or even favor disordered states.
Motofumi Suzuki - One of the best experts on this subject based on the ideXlab platform.
-
thermochromic visualization of the heated region around a microbubble during Marangoni Flow generation
Journal of Nanophotonics, 2021Co-Authors: Kyoko Namura, Toshiki Sono, Samir Kumar, Kaoru Nakajima, Motofumi SuzukiAbstract:We experimentally investigated simultaneous microfluidic control and visualization of a heated region using gold nanoisland/VO2 thin films. By focusing a laser on the film, we photothermally generated an air microbubble in nondegassed water. After the bubble generation, another laser spot was irradiated 48 μm away from the bubble center. As a result, a sudden onset of the rotational Marangoni Flow was observed at 130 ms after the laser was turned on. At the same time, the heated region above 70°C was visualized based on the thermochromic property of the thin film. The heated area did not vary significantly at the onset of the Flow, indicating that there is a threshold temperature or temperature gradient on the bubble surface for generating the rotational Marangoni Flow. To understand the Flow generation, we decreased the distance between the bubble and the laser spot. The resulting visualized heated region suggests that a part of the bubble surface has to be heated above 70°C to generate the rotational Flow. In addition, the heated area during the Flow generation remained small as the distance decreased. The gold nanoisland/VO2 thin film is suitable for understanding and optimizing the rapid Marangoni Flow generation.
-
Microfluidic manipulation based on thermoplasmonic Marangoni effect
2017 6th International Conference on Informatics Electronics and Vision & 2017 7th International Symposium in Computational Medical and Health Technol, 2017Co-Authors: Kyoko Namura, Motofumi SuzukiAbstract:There is a growing need to develop fluid and particle manipulation techniques in microfluidic channels, which are essential for the development of Micro-Total Analysis Systems and Lab on a Chip Devices. The key issue is how to apply forces to the liquid packed in the tiny microfluidic channels. One of the most promising forces for the microfluidic manipulation is “Marangoni force,” which is induced by surface tension gradient on a gas-liquid surface under temperature gradient. Here, we present microfluidic manipulation techniques based on the Marangoni effect controlled by thermoplasmonic effect of gold nanoisland films. Gold nanoparticles absorb light efficiently at their resonant frequency and convert it to heat within several picoseconds. Therefore, a focused light spot on the gold nanoisland film acts as a localized and mobile point-heat-source at a micrometer scale. This heat source allows us to generate a microbubble in water and to give a steep temperature gradient on the bubble surface, which results in the generation of the Marangoni Flow. By tuning the laser spot position against the microbubble, the Flow pattern shows significant change and realizes particle sorting by their size or particle focusing. Recently, we revealed that a further enhancement of the strength of the Marangoni Flow is achieved by the degassing process of the working fluid. When the dissolved gases are removed from the water, a water vapor microbubble with a diameter of 10 μm is generated by the thermoplasmonic heating. This microbubble involves extremely rapid Marangoni Flow, whose speed exceeds 1 m/s at around the microbubble. This rapid Marangoni Flow generation is attributed to the small bubble size, over which the temperature is graded, and the superheat at the bubble surface in contact with the gold nanoisland film.
-
sheathless particle focusing in a microfluidic chamber by using the thermoplasmonic Marangoni effect
Applied Physics Letters, 2016Co-Authors: Kyoko Namura, Kaoru Nakajima, Kenji Kimura, Motofumi SuzukiAbstract:We experimentally investigated the modes of the Marangoni Flow around a microbubble in a 50-μm-thick water chamber and found a transition Flow mode that enables sheathless particle focusing. A temperature gradient was thermoplasmonically induced around the laser spot on a gold nanoisland film, and Marangoni Flows were generated around the microbubble to drive submicron particles dispersed in the water. When the laser spot was slightly displaced from the bubble center, the particles were continuously collected by the bubble underneath and leaked in one direction to form a focused particle stream. The generation of the particle-focusing Marangoni Flow was attributed to the appropriate balance of the temperature gradient in the perpendicular and horizontal directions of the chamber, which was controlled by the laser spot position against the bubble center. Temporally controlling this Flow mode with laser power caused the periodic emission of clustered particles from the bubble underneath. This particle handling method with a thermoplasmonic Marangoni Flow can be useful for improving the efficiency of reaction or sensing processes that take place in a microfluidic chamber.
-
photothermally controlled Marangoni Flow around a micro bubble
Applied Physics Letters, 2015Co-Authors: Kyoko Namura, Kaoru Nakajima, Kenji Kimura, Motofumi SuzukiAbstract:We have experimentally investigated the control of Marangoni Flow around a micro bubble using photothermal conversion. Using a focused laser spot acting as a highly localized heat source on Au nanoparticles/dielectric/Ag mirror thin film enables us to create a micro bubble and to control the temperature gradient around the bubble at a micrometer scale. When we irradiate the laser next to the bubble, a strong main Flow towards the bubble and two symmetric rotation Flows on either side of it develop. The shape of this rotation Flow shows a significant transformation depending on the relative position of the bubble and the laser spot. Using this controllable rotation Flow, we have demonstrated sorting of the polystyrene spheres with diameters of 2 μm and 0.75 μm according to their size.
Jianbin Luo - One of the best experts on this subject based on the ideXlab platform.
-
criterion for reversal of thermal Marangoni Flow in drying drops
Langmuir, 2010Co-Authors: Jianbin Luo, Dan GuoAbstract:The thermal Marangoni Flow induced by nonuniform surface temperature has been widely invoked to interpret the deposition pattern from drying drops. The surface temperature distribution of a drying droplet, although being crucial to the Marangoni Flow, is still controversial. In this paper, the surface temperature in the drop central region is analyzed theoretically based on an asymptotic analysis on the heat transfer in such region, and a quantitative criterion is established for the direction of the surface temperature gradient and the direction of the induced Marangoni Flow of drying drops. The asymptotic analysis indicates that these two directions will reverse at a critical contact angle, which depends not only on the relative thermal conductivities of the substrate and liquid, but also on the ratio of the substrate thickness to the contact-line radius of the droplet. The theory is corroborated experimentally and numerically, and may provide a potential means to control deposition patterns from drying droplets.
-
Marangoni Flow in an evaporating water droplet
Applied Physics Letters, 2007Co-Authors: Jianbin LuoAbstract:Marangoni effect has been observed in many liquids, but its existence in pure water is still a debated problem. In the present work, the Marangoni Flow in evaporating water droplets has been observed by using fluorescent nanoparticles. Flow patterns indicate that a stagnation point where the surface Flow, the surface tension gradient, and the surface temperature gradient change their directions exists at the droplet surface. The deduced nonmonotonic variation of the droplet surface temperature, which is different from that in some previous works, is explained by a heat transfer model considering the adsorbed thin film of the evaporating liquid droplet.
Xuehua Zhang - One of the best experts on this subject based on the ideXlab platform.
-
evaporating pure binary and ternary droplets thermal effects and axial symmetry breaking
Journal of Fluid Mechanics, 2017Co-Authors: Christian Diddens, Michel Versluis, Huanshu Tan, Jgm Hans Kuerten, Xuehua Zhang, Detlef LohseAbstract:The Greek aperitif Ouzo is not only famous for its specific anise-flavoured taste, but also for its ability to turn from a transparent miscible liquid to a milky-white coloured emulsion when water is added. Recently, it has been shown that this so-called Ouzo effect, i.e. the spontaneous emulsification of oil microdroplets, can also be triggered by the preferential evaporation of ethanol in an evaporating sessile Ouzo drop, leading to an amazingly rich drying process with multiple phase transitions (Tan et al., Proc. Natl Acad. Sci. USA, vol. 113 (31), 2016, pp. 8642-8647). Due to the enhanced evaporation near the contact line, the nucleation of oil droplets starts at the rim which results in an oil ring encircling the drop. Furthermore, the oil droplets are advected through the Ouzo drop by a fast solutal Marangoni Flow. In this article, we investigate the evaporation of mixture droplets in more detail, by successively increasing the mixture complexity from pure water over a binary water-ethanol mixture to the ternary Ouzo mixture (water, ethanol and anise oil). In particular, axisymmetric and full three-dimensional finite element method simulations have been performed on these droplets to discuss thermal effects and the complicated Flow in the droplet driven by an interplay of preferential evaporation, evaporative cooling and solutal and thermal Marangoni Flow. By using image analysis techniques and micro-particle-image-velocimetry measurements, we are able to compare the numerically predicted volume evolutions and velocity fields with experimental data. The Ouzo droplet is furthermore investigated by confocal microscopy. It is shown that the oil ring predominantly emerges due to coalescence.
-
evaporating pure binary and ternary droplets thermal effects and axial symmetry breaking
arXiv: Fluid Dynamics, 2017Co-Authors: Christian Diddens, Michel Versluis, Huanshu Tan, Jgm Hans Kuerten, Xuehua Zhang, Detlef LohseAbstract:The Greek aperitif Ouzo is not only famous for its specific anise-flavored taste, but also for its ability to turn from a transparent miscible liquid to a milky-white colored emulsion when water is added. Recently, it has been shown that this so-called Ouzo effect, i.e. the spontaneous emulsification of oil microdroplets, can also be triggered by the preferential evaporation of ethanol in an evaporating sessile Ouzo drop, leading to an amazingly rich drying process with multiple phase transitions [H. Tan et al., Proc. Natl. Acad. Sci. USA 113(31) (2016) 8642]. Due to the enhanced evaporation near the contact line, the nucleation of oil droplets starts at the rim which results in an oil ring encircling the drop. Furthermore, the oil droplets are advected through the Ouzo drop by a fast solutal Marangoni Flow. In this article, we investigate the evaporation of mixture droplets in more detail, by successively increasing the mixture complexity from pure water over a binary water-ethanol mixture to the ternary Ouzo mixture (water, ethanol and anise oil). In particular, axisymmetric and full three-dimensional finite element method simulations have been performed on these droplets to discuss thermal effects and the complicated Flow in the droplet driven by an interplay of preferential evaporation, evaporative cooling and solutal and thermal Marangoni Flow. By using image analysis techniques and micro-PIV measurements, we are able to compare the numerically predicted volume evolutions and velocity fields with experimental data. The Ouzo droplet is furthermore investigated by confocal microscopy. It is shown that the oil ring predominantly emerges due to coalescence.