Buckling of a Bidimensional Solid

We observe buckling, without collapsing, of a solid Langmuir film under uniaxial compression, like an usual elastic plate. The preliminary characterization of this instability shows that, at the threshold, surface tension is strictly positive, amplitude is continuous and wavelength is A, - 6 pm. Without adjustable parameter, we interpret these resulta as a second- order transition due to dipolar interactions between amphiphilic molecules.