Dynamics of spontaneous spreading with evaporation on a deep fluid layer

Dussaud, Anne D.; Troian, Sandra M.

doi:10.1063/1.869546

Cited by 87 publications

(127 citation statements)

References 25 publications

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“…The latter prediction is slightly higher than the reported value of kϭ0.88 obtained in a recent study of silicone oil drops spreading on water. 14,15 The discrepancy may be related to some uncertainty in the measurement of the spreading coefficient as well as the limited number of experiments on which this experimental value is based.…”

Section: ͑1͒mentioning

confidence: 99%

“…Our previous studies 15 have shown that during the first few seconds of spreading, such small volumes still behave as a source of constant concentration to produce a film that advances according to the 3/4 spreading law. A single vertical fluorescent line was drawn at a distance of 4.24 cm away from the point of deposition.…”

Section: A Spreading Behavior Of Nonvolatile Surface Filmsmentioning

confidence: 99%

“…These values agreed very well with previous measurements of the speed of the leading edge, dL/dt, obtained by laser shadowgraphy. 14,15 Besides simply digitizing the displaced dye lines, it is also useful to make comparison with the displacement that would be observed beneath a nonvolatile film traveling at the same speed as the leading edge of the p-xylene film. From the estimated surface velocity of the volatile film, we calculated the Lagrangian position, ͓x,y ͔ϭ͓u⌬t,y ͔, that would instead have resulted had the sublayer flow been purely unidirectional and Blasius-like, as for the silicone oil spreading on water.…”

Section: B Spreading Behavior Of Volatile Filmsmentioning

confidence: 99%

“…14, 15 The tank was filled to a depth of 4 cm with an aqueous dextran carboxy fluorescein solution ͑0.5 mg/l ͒. The addition of this small amount of caged fluorescein did not affect the surface tension of the ultrapure water ͑distilled and deionized 18 M⍀͒ which was measured to be 72.2Ϯ0.3 dyn/cm at 23°C.…”

Section: Flow Tagging Velocimetry Measurementsmentioning

confidence: 99%

“…In lieu of surface seeding techniques to locate the position of the leading edge, we have employed laser shadowgraphy to identify several regions of the spreading film which display strong surface curvature, including the region at the advancing front. 14,15 These experiments were conducted at room temperature in unsaturated conditions in order to enhance the effect of evaporation. The results show that volatile, immiscible films also advance on a deep liquid layer with a power law in time but with a reduced spreading exponent of 1/2 and a weaker dependence on the spreading coefficient than described by Eq.…”

Section: B Leading Edge Of Volatile Surface Filmsmentioning

confidence: 99%

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Fluorescence visualization of a convective instability which modulates the spreading of volatile surface films

1998

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The spontaneous spreading of a thin liquid film along the surface of a deep liquid layer of higher surface tension is a ubiquitous process which provides rapid and efficient surface transport of organic or biological material. For a source of constant concentration, the leading edge of a nonvolatile, immiscible film driven to spread by gradients in surface tension is known to advance as t 3/4 in time. Recent experiments using laser shadowgraphy to detect the advancing front of spreading films indicate, however, that immiscible but volatile sources of constant concentration spread with a reduced exponent according to t 1/2. Using a novel technique whereby fluorescent lines are inscribed in water, we have detected the evolution of a thermal instability beneath the leading edge of volatile films which strongly resembles a Rayleigh-Bénard roll. We propose that the increased dissipation from this rotational flow structure is likely responsible for the reduction in spreading exponent. This observation suggests a conceptual framework for coupling the effects of evaporation to the dynamics of spreading. © 1998 American Institute of Physics. ͓S1070-6631͑98͒01607-9͔ I. SPONTANEOUS SPREADING ON A DEEP LIQUID LAYERWhen a liquid substrate is contacted by a film of lower surface tension, surface traction is produced in proportion to the difference in surface tension between the liquid support and the spreading film. This traction creates rapid and spontaneous flow toward regions of higher surface tension. The speed of the spreading film is known to increase with the magnitude of the spreading coefficient defined by Sϭ␥ 1 Ϫ␥ 2 Ϫ␥ 12 , where ␥ 1 denotes the surface tension of the clean liquid support, ␥ 2 the surface tension of the spreading film, and ␥ 12 the interfacial tension between the spreading film and supporting liquid.1 This spreading coefficient is related to the local gradient in surface tension, ‫,‪x‬ץ/␥ץ‬ through the relation Sϭ͐ 0 L(t) ‫‪x‬ץ/␥ץ‬ dx, where the coordinate x denotes the horizontal or radial direction of spreading and L(t) denotes the length of the surface active film at time t after contact with the liquid support. In the examples discussed below, the gradients in surface tension are caused by variations in the surface concentration, ⌫, of the spreading film where ‫.)‪x‬ץ/⌫ץ()⌫ץ/␥ץ(‪xϭ‬ץ/␥ץ‬ The spontaneous advance of a surface film driven by this type of shear stress is called Marangoni driven spreading, 2 which occurs for positive values of the spreading coefficient. A small scale example of this spreading process occurs during the casting of Langmuir-Blodgett films. In the fabrication of these films, organic or biological molecules are dissolved in a solvent like hexane or carbon tetrachloride which spreads rapidly and spontaneously over the surface of water. The organic solvent, which has a lower surface tension than pure water, acts as the carrier liquid to transport molecules along the water surface under the action of Marangoni stresses. 3 The solvent film eventually evaporates leaving behin...

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Section: ͑1͒mentioning

confidence: 99%

Section: A Spreading Behavior Of Nonvolatile Surface Filmsmentioning

confidence: 99%

Section: B Spreading Behavior Of Volatile Filmsmentioning

confidence: 99%

Section: Flow Tagging Velocimetry Measurementsmentioning

confidence: 99%

Section: B Leading Edge Of Volatile Surface Filmsmentioning

confidence: 99%

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Fluorescence visualization of a convective instability which modulates the spreading of volatile surface films

1998

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Water‐Surface Drag Coating: A New Route Toward High‐Quality Conjugated Small‐Molecule Thin Films with Enhanced Charge Transport Properties

et al. 2020

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Electronic properties of organic semiconductor (OSC) thin films are largely determined by their morphologies and crystallinities. However, solution‐processed conjugated small‐molecule OSC thin films usually exhibit abundant grain boundaries and impure grain orientations because of complex fluid dynamics during solution coating. Here, a novel methodology, water‐surface drag coating, is demonstrated to fabricate high‐quality OSC thin films with greatly enhanced charge transport properties. This method utilizes the water surface to alter the evaporation dynamics of solution to enlarge the grain size, and a unique drag‐coating process to achieve the unidirectional growth of organic crystals. Using 2,8‐difluoro‐5,11‐bis(triethylsilylethynyl)anthradithiophene (Dif‐TES‐ADT) as an example, thin films with millimeter‐sized single‐crystal domains and pure crystallographic orientations are achieved, revealing a significant enhancement (4.7 times) of carrier mobility. More importantly, the resulting film can be directly transferred onto any desired flexible substrates, and flexible transistors based on the Dif‐TES‐ADT thin films show a mobility as high as 16.1 cm2 V−1 s−1, which represents the highest mobility value for the flexible transistors reported thus far. The method is general for the growth of various high‐quality OSC thin films, thus opening up opportunities for high‐performance organic flexible electronics.

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Kirigami‐Inspired Stretchable Conjugated Electronics

Zhang

Tang

et al. 2019

Adv Elect Materials

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The conducting nature of π-conjugated polymers enables the strain-dependent electronic and capacitance sensor. Its light-emitting nature facilitates its optical strain sensing due to the emission change under strain, which is unaccessible in the conductor and insulator materials. The semiconducting materials used to form stretchable components are typically achieved by transferring the films onto the soft stretchable substrate. Random polymer chain distribution with defects would exist, and a significant amount of cracks could occur during the transferring process. The geometric engineering has been applied to simultaneously achieve high stretchability and conductivity of conjugated polymers. [20-22] In this context, the kirigami, which refers to cutting materials into certain patterns to acquire desirable structures, has inspired the programmable stretchable electronics. [23,24] The kirigami structures reveal excellent potential to achieve the desired stretchable electronic properties. Here, we report a liquid/air assembly to grow large-area freestanding poly2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene (MEH-PPV) nanosheets, while their unique electronic and light-emitting properties arise from the electron coupling strength between π-stacking units and further high degree of molecular packing arrangements. The freestanding MEH-PPV nanosheets at the water-air interface ensure the conformal contact onto various surfaces. These contribute to the development of conformal sensors based on the sensitivity of band gap to π-π stacking. Furthermore, the geometric engineering with kirigami structures on the freestanding MEH-PPV films not only extends its stretchability but also sustains its conductive and light-emitting properties, which significantly enhance its stretchable applications.

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Dynamics of spontaneous spreading with evaporation on a deep fluid layer

Cited by 87 publications

References 25 publications

Fluorescence visualization of a convective instability which modulates the spreading of volatile surface films

Fluorescence visualization of a convective instability which modulates the spreading of volatile surface films

Water‐Surface Drag Coating: A New Route Toward High‐Quality Conjugated Small‐Molecule Thin Films with Enhanced Charge Transport Properties

Kirigami‐Inspired Stretchable Conjugated Electronics

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