Laser-Induced Marangoni Convection in the Presence of Surfactant Monolayers

Gugliotti, Marcos; Baptista, Maurı́cio S.; Politi, Mário José

doi:10.1021/la020508a

Cited by 43 publications

(48 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This simple and direct method has been used before with tap water, and the results obtained are in good agreement with the literature. [17][18][19] For the experiments presented here, the uncertainty in the measurements of the water volume remaining in the recipients (using Pasteur pipettes and graduated cylinders) was less than 3%. Fatty alcohols as hexadecanol (99%) and octadecanol (95%) were purchased from Aldrich and used without further purification.…”

Section: Methodsmentioning

confidence: 99%

Reduction of evaporation of natural water samples by monomolecular films

Gugliotti¹,

Baptista²,

Politi³

2005

J. Braz. Chem. Soc.

Self Cite

View full text Add to dashboard Cite

A capacidade de filmes monomoleculares de álcoois graxos em reduzir a evaporação de amostras naturais de água, coletadas em dois reservatórios de São Paulo (Guarapiranga e Billings), foi estudada em laboratório. As reduções da evaporação foram determinadas diretamente, medindo-se o volume de água evaporado dos recipientes de teste após certo tempo. Filmes mistos de hexadecanol e octadecanol apresentaram alto potencial de redução da evaporação (até 57%) e persistência na superfície da água, por cerca de 48 horas. Uma breve discussão sobre a melhor eficiência desses filmes mistos na redução da evaporação de água é também apresentada.The ability of monomolecular films of fatty alcohols in reducing evaporation of natural water samples collected from two reservoirs in São Paulo (Guarapiranga and Billings) was studied in the laboratory. Evaporation reductions were determined directly by measuring the volume of water evaporated from the test recipients after a certain period of time. Mixed films of hexadecanol and octadecanol showed high potential of evaporation reduction (up to 57%) and persistence on the water surface of ca. 48 hours. A brief discussion on the better efficiency of these mixed films in reducing water evaporation is also presented. Keywords: water, evaporation, fatty alcohols, monomolecular films, surface tension IntroductionWater is the most precious natural resource available to mankind. Most of our usable fresh water is retained in lakes and reservoirs, but this type of storage allows for the greatest loss of water by evaporation. The increasing demand for municipal and industrial fresh water, and the current increase in the global temperature indicate that it is necessary to employ techniques for reducing evaporation aiming at the conservation of water supplies.It has been known for a long time that monomolecular films of certain surfactants can retard water evaporation. 1 This seems to be the only viable technology for reducing the evaporative losses of water from reservoirs. 2 For many years, important studies in laboratory scale were carried out in order to identify the optimal substances and conditions for reducing water evaporation. [3][4][5] Among the surfactants tested, biodegradable fatty alcohols of low toxicity presented the highest resistance to water evaporation, especially 1-hexadecanol and 1-octadecanol. 2 The first field experiment was conducted in Australia in the beginning of the 50's, and the obtained evaporation reductions of 30% called attention of many research groups and governments around the world. 6,7 In the following decades, several experimental and theoretical works were published, and the main conclusions were collected in a review published in 1986. 8 Although the spreading of a monomolecular film on the surface of a reservoir has been considered as an alternative technology for fresh water conservation by the United Nations Environment Programme, only a few investigations on this subject have been reported in the last years. 9 Among the most recent works on this subje...

show abstract

Section: Methodsmentioning

confidence: 99%

Reduction of evaporation of natural water samples by monomolecular films

Gugliotti¹,

Baptista²,

Politi³

2005

J. Braz. Chem. Soc.

Self Cite

View full text Add to dashboard Cite

show abstract

“…This is consistent with other examples of thermo-solutal competition where the thermal and solutal Marangoni mechanisms are almost in exact balance. 10,11 …”

Section: Marangoni Stresses and Interface Velocitymentioning

confidence: 99%

“…In practical situations, further complications appear when the thermocapillary effect is conjugated with the transport of surfactant molecules. 10,11 Indeed, the interface motion advects the surfactant molecules and can lead to the accumulation of these molecules at the stagnation points on the drop, leading to additional gradients of stress.…”

Section: Introductionmentioning

confidence: 99%

“…11 A recent series of articles has explored the use of laser heating to manipulate drops of water in oil travelling inside microfluidic channels. [12][13][14] The laser in these experiments is chosen to heat only the water phase, it remains stationary and is focused to a waist of a few microns, small compared to the typical drop size (100 µm).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Laser-Induced Force on a Microfluidic Drop: Origin and Magnitude

Verneuil

Cordero

Gallaire³

et al. 2009

Langmuir

View full text Add to dashboard Cite

The localized heating produced by a tightly focused infrared laser leads to surface tension gradients at the interface of microfluidic drops covered with surfactants, resulting in a net force on the drop whose origin and magnitude are the focus of this paper. First, by colocalization of the surfactant micelles with a fluorescent dye, we demonstrate that the heating alters their spatial distribution, driving the interface out of equilibrium. This soluto-capillary effect opposes and overcomes the purely thermal dependence of the surface tension, leading to reversed interfacial flows. As the surface of the drop is set into motion, recirculation rolls are created outside and inside the drop that we measure using time-resolved micro-Particle Image Velocimetry. Second, the net force produced on the drop is measured using an original microfluidic design. For a drop 300 µm-long and 100 µm wide we obtain a force of 180 † Laboratoire d'Hydrodynamique (LadHyX), Ecole Polytechnique, 91128 Palaiseau, France ‡ Laboratoire J.A. Dieudonné, Université de Nice Sophia-Antipolis, 06108 Nice, France § Current address:Department of Physics, University of Pennsylvania, Philadelphia, PA 1 Emilie Verneuil et al.Laser-induced force on a drop nN for a laser power of 100 mW. This micro-dynanometer further shows that the magnitude of the heating, which is determined by the laser power and its absorption in the water, sets the magnitude of the net force on the drop. On the other hand, the dynamics of the force generation is limited by the time scale for heating which has independently been measured to be τ Θ = 4 ms. This time scale sets the maximum velocity that the drops can have and still be blocked, by requiring that the interface passes the laser spot in a time longer than τ Θ . The maximum velocity is measured at U max = 0.7 mm/s for our geometric conditions. Finally, a scaling model is derived that describes the blocking force in a confined geometry as the result of the viscous stresses produced by the shear between the drop and the lateral walls.

show abstract

“…tension, density, and/or viscosity. Therefore, some convection can also be caused by local cooling or heating (e.g., Gugliotti et al 14 …”

mentioning

confidence: 99%