Thermocapillary motion of hybrid drops

Rosenfeld, Liat; Lavrenteva, Olga M.; Nir, A.

doi:10.1063/1.2958292

Cited by 12 publications

(7 citation statements)

References 25 publications

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“…These changes might lead to separation or full engulfment. They also simulated the motion of a compound drop due to Marangoni effect which can be unpredictably against the temperature gradient under specific conditions [ 169 ].…”

Section: Thermocapillary-induced Droplet/bubble Actuationmentioning

confidence: 99%

Thermocapillarity in Microfluidics—A Review

2016

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This paper reviews the past and recent studies on thermocapillarity in relation to microfluidics. The role of thermocapillarity as the change of surface tension due to temperature gradient in developing Marangoni flow in liquid films and conclusively bubble and drop actuation is discussed. The thermocapillary-driven mass transfer (the so-called Benard-Marangoni effect) can be observed in liquid films, reservoirs, bubbles and droplets that are subject to the temperature gradient. Since the contribution of a surface tension-driven flow becomes more prominent when the scale becomes smaller as compared to a pressure-driven flow, microfluidic applications based on thermocapillary effect are gaining attentions recently. The effect of thermocapillarity on the flow pattern inside liquid films is the initial focus of this review. Analysis of the relation between evaporation and thermocapillary instability approves the effect of Marangoni flow on flow field inside the drop and its evaporation rate. The effect of thermocapillary on producing Marangoni flow inside drops and liquid films, leads to actuation of drops and bubbles due to the drag at the interface, mass conservation, and also gravity and buoyancy in vertical motion. This motion can happen inside microchannels with a closed multiphase medium, on the solid substrate as in solid/liquid interaction, or on top of a carrier liquid film in open microfluidic systems. Various thermocapillary-based microfluidic devices have been proposed and developed for different purposes such as actuation, sensing, trapping, sorting, mixing, chemical reaction, and biological assays throughout the years. A list of the thermocapillary based microfluidic devices along with their characteristics, configurations, limitations, and improvements are presented in this review.

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Section: Thermocapillary-induced Droplet/bubble Actuationmentioning

confidence: 99%

Thermocapillarity in Microfluidics—A Review

2016

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“…The motion of a partially engulfed compound drop induced solely by gravity and buoyancy was studied by Oguz (1987) and Vuong & Sadhal (1989a). Their derivations were revisited also in our recent paper (Rosenfeld et al 2008). Due to the linearity of the problem, the velocity of a partially engulfed drop moving under the simultaneous effect of gravity and thermocapillarity can be obtained by a simple superposition of the two results.…”

Section: Further Discussion and Conclusionmentioning

confidence: 99%

“…are determined using the boundary conditions (2.3)-(2.6). The procedure of finding these coefficients was developed by Rosenfeld et al (2008) following methods of Oguz (1987) and Vuong and Sadhal (1989a), who solved the problem of the compound drop motion in the absence of Marangoni effect. The details of methods of calculation are given in the Appendix.…”

Section: Methods Of Solution Flow Fieldmentioning

confidence: 99%

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On the thermocapillary motion of partially engulfed compound drops

2009

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In this work the thermocapillary-induced motion of partially engulfed compound drops is considered. This phenomenon occurs in many natural and technological processes in which heat is exchanged between such hybrid drops and the medium around them through the interfaces. Two types of thermal fields and the resulting motions are studied; flow induced by an external temperature gradient and spontaneous thermocapillary motion. For the first flow type, it was found that, in general, the motion is induced in the direction of the temperature gradient. However, under certain physical conditions and drops' configuration a motion against the temperature gradient may be observed. In the second case, spontaneous thermocapillary motion, the compound drop moves due to surface tension gradients which result from the geometric non-uniformity of the system. Results are presented for several parameters such as configuration of the compound drop, viscosity, thermal conductivity ratio, the dependence of the various interfacial tensions on temperature and the volume ratio of the phases within the drop.

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“…Literature reports show results about the laser beam interaction with droplets that contain single liquids or mixtures of immiscible materials produced in different surrounding environments (which may be either liquids or air/gases) [4,5].…”

Section: Introductionmentioning

confidence: 99%

Unresonant interaction of laser beams with microdroplets

Pascu¹,

Popescu²,

Ticoş³

et al. 2012

J. Eur. Opt. Soc.-Rapid Publ.

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The interaction of distilled water droplets (volumes of 3-4 µl) with pulsed laser beams emitted at 532 nm is described. At 532 nm the distilled water absorption is very low and the interaction of a water droplet with the laser radiation is dominated by unresonant phenomena. In this case, following the collision of the laser beam with a droplet in suspended position in air, its deformations and mechanical vibrations are produced. The conditions in which the droplets lose material as a consequence of the impact with laser beams are explored. The effects produced on the droplet were studied pulse by pulse and depend on: droplet's content, beam wavelength, power and focusing, irradiation geometry and adhesion of the droplet to the capillary on which it is suspended. The laser pulses energies were varied in four steps: 0.25 mJ, 0.4 mJ, 0.7 mJ and 1 mJ. The laser pulse full time width at half maximum was 5ns and the typical beam waist diameter on the droplet was 90 µm; the beam had a relatively low divergence around the focus point. The droplet's shapes evolution is visualised by recordings performed at 10 kframes/second. Following a droplet interaction with the laser beam one may also produce at a controlled moment in time, nanodroplets propagating at high (probably supersonic) speeds and microdroplets propagating at slower speeds. One may also produce suspended droplets of smaller dimensions than the initial one as well as micro/nano gas bubbles in the suspended droplet's material/volume. In a second set of experiments the behaviour of the microdroplets of Rhodamine 6G in distilled water was recorded at high speed, at resonant interaction with similar laser pulses, and at the same power levels. The phenomena considering that the droplets contents are Newtonian liquids produced at interaction with the laser beams, are discussed.

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Thermocapillary motion of hybrid drops

Cited by 12 publications

References 25 publications

Thermocapillarity in Microfluidics—A Review

Thermocapillarity in Microfluidics—A Review

On the thermocapillary motion of partially engulfed compound drops

Unresonant interaction of laser beams with microdroplets

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