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 𝒯 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 2θ ( f = 2𝒯 cos θ), which allows us to measure 𝒯. (ii) Moved sinusoidally, we generate “triplons” of wavevectors q along the line. In the gravity regime ( q κ - 1 < 1, where κ - 1 is the capillary length), the measured dispersion relation is ω( q ) ≃ q 1.51 ± 0.05 . An improved version of our previous dynamical model gives an exponent 3/2.