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Europhys. Lett.
Volume 64, Number 5, December 2003
Page(s) 709 - 715
Section Interdisciplinary physics and related areas of science and technology
Published online 01 November 2003
DOI: 10.1209/epl/i2003-00283-5
Europhys. Lett., 64 (5) , pp. 709-715 (2003)

Two-dimensional shear modulus of a Langmuir foam

S. Courty1, B. Dollet1, F. Elias2, P. Heinig3 and F. Graner1

1  Laboratoire de Spectrométrie Physique (UMR 5588 CNRS, Université J. Fourier Grenoble 1) BP 87, F-38402 Saint Martin d'Hères cedex, France
2  Laboratoire des Milieux Désordonnés et Hétérogènes (UMR 7603 CNRS, Université Paris 6) case 78, 4 place Jussieu, F-75252 Paris cedex 05, France
3  Max Planck Institut of Colloids and Interfaces Am Mühlenberg 1, D-14476 Golm, Germany

(Received 13 May 2003; accepted in final form 16 September 2003)

We deform a two-dimensional (2D) foam, created in a Langmuir monolayer, by applying a mechanical perturbation, and simultaneously image it by Brewster-angle microscopy. We determine the foam stress tensor (through a determination of the 2D gas-liquid line tension, $2.35 \pm 0.4$ $\un{pJ\cdot m^{-1}}$) and the statistical strain tensor, by analyzing the images of the deformed structure. We deduce the 2D shear modulus of the foam, $\mu= 38 \pm 3$ $\un{nN\cdot m^{-1}}$. The foam effective rigidity is predicted to be $35 \pm 3$ $\un{nN\cdot m^{-1}}$, which agrees with the value $37.5 \pm 0.8$ $\un{nN\cdot m^{-1}}$ obtained in an independent mechanical measurement.

83.80.Iz - Emulsions and foams.
68.18.-g - Langmuir-Blodgett films on liquids.
62.20.Dc - Elasticity, elastic constants.

© EDP Sciences 2003