Periodic compression-expansion cycles

In a second technique, a freshly swept surface of a dilute surfactant solution is subjected to periodic compression-expansion cycles. With the... 

The amphiphilic material to be studied is dissolved at a known concentration in a volatile solvent which is not miscible with water and a known quantity is spread at the water surface using a micropipette. In order to study the physical properties of the film thus formed, one needs to be able to confine the film to a definite area and to be able to vary this area at will. It might appear that it would be equally possible to maintain a constant area and vary the amount of material which is spread. For the majority of materials this latter procedure is not satisfactory as equilibrium is not arrived at in a reasonable period of time and this method would not allow one to take the material through successive cycles of compression and expansion. We thus turn to a discussion of the various ways in which a film can be confined and its area varied in a systematic manner. Leaving aside methods which are really only of historical interest, for which reference should be made to the book by... 

The word cyclic requires that the system be restored periodically to its original state. In the case of a gas in a piston-and-cylinder assembly the expansion and compression back to the original state constitute a complete cycle. If the process... 

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