Crack Patterns in Drying Process Show Memories Contained Inside Granular Networks

We perform experiments in which we dry the mixture of powder and water. When the proportion of water to powder in the mixture is high and the mixture is Newtonian viscous fluid, crack patterns that will appear after the drying process are cellular. On the other hand, when the proportion of water to powder is low and thus the mixture becomes visco-plastic with a non-zero yield stress, the morphology of crack patterns can change from homogeneous cellular patterns to inhomogeneous patterns. For example, if we add initial vibration to the container of the visco-plastic mixture, we get a laminar crack pattern, the direction of which is perpendicular to the initial external vibration. That is, when the mixture is visco-plastic, the granular network inside the mixture remembers the direction of the initial external vibration.