Imprinting Memory into Paste and Its Visualization as Crack Patterns in Drying Process

Abstract

In the drying process of a paste, we can imprint a memory into the paste that determines how it will be broken in the future. That is, if we vibrate the paste before it is dried, it remembers the direction of the initial external vibration, and the morphology of the resultant crack patterns is determined solely by the memory of this direction. The morphological phase diagram of crack patterns and the rheological measurement of the paste show that this memory effect is induced by the plasticity of the paste.

Evolution of mud-crack patterns during repeated drying cycles

“…Information about crack positions must be stored in the clay layer, across multiple wettings and dryings. A similar concept was demonstrated by Nakahara and Matsuo, 8 who vibrated slurries prior to drying them. The resulting cracks were largely co-aligned with the direction of vibration.…”

Effect of Interaction on the Formation of Memories in Paste

“…We had confirmed that this memory lasts at least one month. 12) In that experiment, we set a container in a small box, poured a paste into the container, vibrated the container for a short time, and kept the container at rest for one month. Since the container was kept in a small box, the humidity inside the small box became soon saturated, and the paste was kept wet without drying for one month.…”

“…[9][10][11] Recently, it has been reported that paste remembers the direction of external fields and the morphology of desiccation cracks can be controlled by memory effects of paste. [12][13][14] If we mix powder with water, pour the mixture into a container to make a thin layer, and dry it at a room temperature, desiccation cracks emerge with characteristic sizes of these fragments proportional to the depth of the mixture. [15][16][17][18] When the mixture contains a lot of water, it can be regarded as a viscous Newtonian fluid, and we usually get isotropic and cellular desiccation crack patterns.…”

“…Due to the plasticity, paste remembers the direction of external field, such as vibration and flow, and the direction of desiccation crack propagation is determined by the memory effect of the paste. [12][13][14] For example, a water-poor paste remembers the direction of vibration. If we vibrate a water-poor paste horizontally for some time as short as 1 min, then stop the vibration and dry it slowly at a room temperature for a long time from days to weeks, the paste is found to remember the direction of the initial vibration, so that the desiccation cracks propagate along the direction perpendicular to the direction of the initial vibration the paste got days or weeks ago.…”

“…We confirmed that this memory lasts at least one month by starting the drying process one month after the initial vibration. 12) What will happen when we vibrate a water-rich paste? Of course, even if we call this water-rich, it contains certain amount of colloidal particles as long as it holds plasticity.…”