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Line Tension Effect on Alkane Droplets Near the Wetting Transition

  • A. D. Dussaud (a1) and M. Vignes-Adler (a2)

Abstract

We have investigated n-octane droplets resting on the surface of sodium chloride solutions as a function of the salt concentration in a saturated, closed cell. For high salt concentration, the system approaches a wetting transition : the contact angles are very small (∼ 1°), the macroscopic droplet is unstable, and it breaks up spontaneously into microdroplets. The stable polydisperse population of microdroplets (5 μm < r < 250 μm) allowed us to analyze the dependence of the contact angle on droplet size. Because of the low contact angle values, accurate measurement ofcontact angles was obtained by interferometry. Moreover the accuracy of the classical method was significantly improved through the systematic use of three wavelengths. The relationship between the contact angle and the size droplet size indicated a positive line tension, τ, and the order of magnitude of τ was in good agreement with the theoretical prediction, τ, varies between (8.6 ± 0.9). 10−11 N and (1 ± 0.1).10−9 N and was dependent on the salt concentration. The positive sign of τ and its significant effect on droplet shape were related to the fact that the system was approaching the wetting transition.

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Line Tension Effect on Alkane Droplets Near the Wetting Transition

  • A. D. Dussaud (a1) and M. Vignes-Adler (a2)

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