450:: binding forces between the substrate atoms and the film atoms can cause the total energy to decrease. In that case, the lowest energy configuration for the body would be one where as many film atoms as possible are as close as possible to the substrate. That would result in an infinitely thin film, infinitely widely spread out over the substrate. In reality, the effect of adherent wetting (causing surface maximization) and the effect of surface tension (causing surface minimization) would balance each other out: the stable configuration can be a droplet, a puddle, or a thin film, depending on the forces that work on the body.
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During the late stages of draining, sharp-edged black spots start to form. These spots are significantly thinner (< 100 nm) than the normal soap film, giving rise to their black interference colour. Whether black spots can form depends on the concentration of the soap, and moreover there are
544:
If a soap film is unstable, it ends by bursting. A hole is created somewhere in the film and opens very rapidly. Surface tension indeed leads to surface minimization and, thus, to film disappearance. The hole aperture is not instantaneous and is slowed by the liquid inertia. The balance between the
506:
are well chosen and the atmospheric humidity and air movements are suitably controlled, a horizontal soap film can last from minutes to hours. In contrast, a vertical soap film is affected by gravity and so the liquid tends to drain, causing the soap film to thin at the top. Colour depends on film
413:
Even in the presence of stabilizing surfactants, a soap film does not last forever. Water evaporates with time depending on the humidity of the atmosphere. Moreover, as soon as a film is not perfectly horizontal, the liquid flows toward the bottom due to gravity and the liquid accumulates at the
394:
Surfactants stabilize films because they create a repulsion between both surfaces of the film, preventing it from thinning and consequentially bursting. This can be shown quantitatively through calculations relating to
410:. This gives some elasticity to the interface: if surface concentrations are not homogeneously dispersed at the surface, Marangoni forces will tend to re-homogenize the surface concentration (see figure 2).
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Newton black films, around 4 nm in thickness, require a higher electrolyte concentration. In these films the outer soap surfaces have effectively snapped together and pinched out most of the inner
588:
536:
As drainage continues, the black spots eventually take over the entire soap film, and despite its extreme thinness, the final black film can be quite stable and can survive for many minutes.
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Daily experience shows that soap bubble formation is not feasible with water or with any pure liquid. Actually, the presence of soap, which is composed at a molecular scale of
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628:
434:. In order to minimize its energy, a droplet of liquid in free space naturally assumes a spherical shape, which has the minimum surface area for a given volume.
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Figure 3: thin film interference in a soap bubble. Notice the golden yellow colour near the top where the film is thin and a few even thinner black spots
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If the information is appropriate for the lead of the article, this information should also be included in the body of the article.
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Figure 2: Marangoni surface forces due to inhomogeneities in surfactants concentration. The arrows represent the force direction
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Figure 4: Picture of a film taken during its generation. The film is pulled out of a soapy solution and drains from the top.
486:
of internally reflected light), but rather is the same as the phenomenon causing the colours in an oil slick on a wet road.
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is the energy that is required to produce the surface, per unit area. A film—like any body or structure—prefers to exist in
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thickness, which accounts for the coloured interference fringes that can be seen at the top of figure 4.
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351:. Soap films can be used as model systems for minimal surfaces, which are widely used in mathematics.
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about governing physics, links with adsorption and nucleation, relevance in science and daily life.
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and are determined by the thickness of the film. This phenomenon is not the same as the origin of
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Moreover, surfactants make the film more stable toward thickness fluctuations due to the
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part. Thus, they are arranged preferentially at the air/water interface (see figure 1).
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Please expand the article to include this information. Further details may exist on the
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403:(the surfactants can not interlace) and electrostatic (if surfactants are charged).
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come into contact, they merge and a thin film is created in between. Thus,
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of (internally and externally) reflected light waves, a process called
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Figure 1: Organisation of surfactants at both surfaces of the soap film
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Capillarity and wetting phenomena : drops, bubbles, pearls, waves
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forces of inertia and surface tension leads to the opening velocity:
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contains information that is not included elsewhere in the article
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671:. Brochard-Wyart, Françoise., Quéré, David. New York: Springer.
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to the atoms of a substrate. The latter phenomenon is called
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and films can exist in of the presence of other forces, like
339:(usually water-based) surrounded by air. For example, if two
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709:
Pugh, Robert J. (2016). "Soap bubbles and thin films".
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Common black films, around 50 nm in thickness, and
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Figure 5: Magnified view of black spots in a soap film
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Shapes. Nature's
Patterns: a tapestry in three parts
583:{\displaystyle V={\sqrt {\frac {2\gamma }{\rho h}}}}
145:. Unsourced material may be challenged and removed.
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may be too technical for most readers to understand
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422:From a mathematical point of view, soap films are
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347:are composed of a network of films connected by
418:Importance of surface tension: minimal surfaces
414:bottom. At the top, the film thins and bursts.
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838:
383:, which means they are molecules with both a
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53:Learn how and when to remove these messages
1064:Giant bubbles, coloured bubbles, freezing
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313:Learn how and when to remove this message
255:Learn how and when to remove this message
205:Learn how and when to remove this message
103:Learn how and when to remove this message
87:, without removing the technical details.
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16:Thin layers of liquid surrounded by air
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470:colours of a soap film are caused by
85:make it understandable to non-experts
804:. Oxford University Press. pp.
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399:. The main repulsion mechanisms are
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143:adding citations to reliable sources
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432:a state of minimum potential energy
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744:"Comments on a Ruptured Soap Film"
667:Gennes, Pierre-Gilles de. (2004).
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879:Experiments and characterization
34:This section has multiple issues.
757:(6). AIP Publishing: 1128–1129.
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610:is the liquid surface tension,
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42:or discuss these issues on the
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713:. Cambridge. pp. 84–111.
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853:Foam scales and properties
751:Journal of Applied Physics
630:is the liquid density and
524:two types of black films:
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742:Culick, F. E. C. (1960).
711:Bubble and Foam Chemistry
444:intermolecular attraction
325:Not to be confused with
650:is the film thickness.
603:{\displaystyle \gamma }
482:colours (caused by the
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476:thin film interference
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282:is missing information
1008:double bubble theorem
882:Transport properties
808:–67, 81–97, 291–292.
796:Ball, Philip (2009).
699:Ball, 2009. pp. 61–67
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623:{\displaystyle \rho }
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335:are thin layers of
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1055:Interferences
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1120:Potts' model
1014:Giant films
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931:ellipsometry
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341:soap bubbles
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233:lead section
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137:Please help
132:verification
129:
99:
90:
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50:
43:
37:
36:Please help
33:
1087:Coalescence
900:Surfactants
885:Irisations
867:Generation
511:Black spots
504:surfactants
472:interfering
389:hydrophilic
385:hydrophobic
381:amphiphilic
377:surfactants
154:"Soap film"
1165:Categories
1091:coarsening
1081:metastable
1039:T1 process
979:, bursting
922:adsorption
873:Stability
870:Structure
654:References
484:refraction
468:iridescent
333:Soap films
327:Soap opera
165:newspapers
39:improve it
1147:Aquafoams
1125:acoustics
1108:acoustics
1046:acoustics
983:Marangoni
977:dewetting
779:0021-8979
618:ρ
598:γ
571:ρ
566:γ
355:Stability
296:June 2020
288:talk page
245:June 2020
195:June 2020
93:June 2020
45:talk page
1143:topology
1100:rheology
1095:drainage
1050:electric
1034:drainage
907:Micelles
876:Dynamic
687:51559047
540:Bursting
490:Drainage
442:and the
1139:Packing
1093:, foam
1026:shape,
1020:Bubbles
759:Bibcode
532:liquid.
480:rainbow
454:Colours
448:wetting
440:gravity
436:Puddles
179:scholar
79:Please
888:Maths
864:Scale
812:
777:
725:
685:
675:
590:where
401:steric
387:and a
337:liquid
181:
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152:
1083:state
1032:foam
956:Films
747:(PDF)
345:foams
186:JSTOR
172:books
1141:and
1070:Foam
968:DLVO
935:Xray
894:Fun
810:ISBN
775:ISSN
723:ISBN
683:OCLC
673:ISBN
466:The
158:news
911:HLB
767:doi
715:doi
502:If
141:by
83:to
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