Competition of intrinsic and topographically imposed patterns in Benard-Marangoni convection

The structure of Benard-Marangoni convection cells can be controlled by per iodic topographic patterns on the heated surface that generates the convect ion. When the periodicity of the topographic pattern matches the intrinsic periodicity of the convection cells, a convective pattern is formed that is 1:1 commensurate with the topographic pattern. Arrays of hexagonal, square , and triangular convection cells were generated over the appropriately des igned topographic patterns, and visualized by infrared imaging. For imposed patterns with periodicity in two dimensions, as the ratio of the intrinsic and perturbing length scales changes, the pattern of the convection cells shows sharp transitions between different patterns commensurate with the im posed pattern. For imposed patterns with periodicity in one dimension (i.e. , lines) the convection cells use the unconstrained dimension to adapt cont inuously to the external perturbation. Topographically controlled convectio n cells can be used to assemble microscopic particles into externally switc hable regular lattices. (C) 2001 American Institute of Physics.