Evolution of hexagonal patterns from controlled initial conditions in a Bénard-Marangoni convection experiment.

We report quantitative measurements of both wave number selection and defect motion in nonequilibrium hexagonal patterns. A novel optical technique ("thermal laser writing") is used to imprint initial patterns with selected characteristics in a Bénard-Marangoni convection experiment. Initial patterns of ideal hexagons are imposed to determine the band of stable pattern wave numbers while initial patterns containing an isolated penta-hepta defect are imprinted to study defect propagation directions and velocities. The experimental results are compared to recent theoretical predictions.