The Life and Death of a Free Soap Film

Authors: H. C. Mayer, R. Krechetnikov, "The Life of a Free Soap Film," ArXiv, 12 Oct 2010: http://arxiv.org/abs/1010.2529

"The Life of a Free Soap Film" is a fluid dynamics video for the Gallery of Fluid Motion intended to showcase the novel experimental techniques that we have developed in our laboratory to study the retraction of planar liquid films of various shapes and sizes as well as other film properties not accessible before. Unlike previous experimental studies that have used rupture to initiate the retraction of a liquid film from a point, we can produce the uniform release of a soap film along a straight edge up to many centimeters in length and capture the subsequent retraction of the film and details concerning the development of the edge using high speed photography. This video only hints at the astonishing life of a "free" soap films.

The soap films used in our experiments are formed from a solution composed of deionized water, 4% glycerol, and sodium dodecyl sulfate surfactant at the
critical micelle concentration. The shape and size of the soap films are set by the nichrome wire frames on which they are formed; the size of the wires ranges between 50 gauge (25 micrometers diameter) and 36 gauge (127 micrometers diameter). The wire frames are mounted to a precision stepper motor which allows the frames to be withdrawn vertically from the solution with a constant speci ed velocity.

Soap films produced in this manner are on the order of 1 micrometer thick. The wire frame acts as a resistor in a custom-built high voltage circuit connected to a capacitor charged to several thousand volts. When the capacitor is discharged, Joule heating of the wire frame causes the soap film immediately in contact with the frame to rapidly boil thereby detaching the soap film uniformly along the entire frame.

The video starts with a movie showing the soap film retraction by point rupture, the more traditional method of film rupture from a point by impacting the film with a cotton swab. Our experimental technique allows us to go beyond the classical study of the retraction of liquid films from a point and to capture the retraction of planar liquid films detached from their edges. The movie shows the soap film retraction for square, rectangular and circular frames.

Category:

Science & Technology

Tags:

• science
• physics
• fluid mechanics
• planar liquid sheets
• liquid films
• soap

[xXCatalystic37Xx]

This video is fantastic. Did you do a quantitative analysis on the retraction of the film, or was it purely qualitative? What was the insight gained from this other then seeing the retraction of the film?