Fast dynamics of floating triple lines

We study the contour (or contact) line of a large water puddle floating on an organic liquid substrate. The line tension F is a two-dimensional analogue of surface tension. We manipulate the line through a vertical metallic rod. (i) When stretched by a horizontal force f, the line makes a kink characterized by an angle 20 (f = 2 F cos 0), which allows us to measure F. (ii) Moved sinusoidally, we generate "triplons" of wavevectors q along the line. In the gravity regime (qκ - 1 < 1, where κ - 1 is the capillary length), the measured dispersion relation is ω(q) = q 1 . 5 1 γ 0 . 0 5 . An improved version of our previous dynamical model gives an exponent 3/2.