Experimental Demonstration of the Role of Anisotropy in Interfacial Pattern Formation

We impose anisotropy in modified Hele-Shaw experiments by engraving a grid on one of the plates. Without anisotropy, the dynamics is dominated by tip bifurcations leading to a branched ramified structure. With anisotropy, a dendritic pattern forms, in qualitative agreement with the prediction of recent studies of local growth models.