Imprinting memory into paste to control crack formation in drying process

Abstract

In the drying process of paste, we have experimentally found a method to imprint into paste the direction of future crack propagation. In the method, we vibrate the paste before it is dried. As the paste dries, an anisotropic crack pattern, such as a lamellar crack pattern, appears with the directions of these cracks all perpendicular to the direction of the initial vibration. By performing rheological measurement of paste and by making a morphological phase diagram of crack patterns, we find that the plasticity of paste plays an important role in the memory effect.

Continuum theory of memory effect in crack patterns of drying pastes

“…This is plausible for CaCO 3 , which consists of spherical particles [3,4]. On the other hand, magnesium carbonate hydroxide is not expected to exhibit isotropy in this sense, as its particles are disk-like [5] and therefore can exhibit anisotropy similar to that of liquid crystals.…”

“…As the plastic behavior of soft glassy materials has been attracting increasing interest [1], it was reported by Nakahara and Matsuo [2,3,4] that a drying paste exhibits a memory effect. They observed a drying process for a paste containing calcium carbonate (CaCO 3 ) and water in a shallow container in order to study the resulting crack pattern.…”

Effect of disorder on shrinkage-induced fragmentation of a thin brittle layer

“…Experiments performed with suspensions of coffee powder [3], clay [4,5], and calcium carbonate [6] have revealed polygonal crack patterns with a high degree of isotropy of the crack orientation. Along the cellular crack network the thin layer breaks up into pieces such that the evolution of the crack pattern is usually characterized by the average size (linear extension, area, mass) of fragments, by the evolution of the mass distribution of fragments [1], and by the degree of opening of the cracks [5] as function of the shrinkage strain or time.…”

“…It is of great interest how to control the structure of shrinkage-induced two-dimensional crack patterns [1,6,7] also due to its high potential for technological applications [8,9]. Recently, it has been demonstrated experimentally for dense calcium carbonate and magnesium carbonate hydroxide pastes that applying mechanical excitation by means of vibration or flow of the paste the emerging desiccation crack pattern remembers the direction of excitation [6,7]: for vibration and flow the primary crack orientation becomes perpendicular and parallel to the direction of excitation, respectively.…”

“…Recently, it has been demonstrated experimentally for dense calcium carbonate and magnesium carbonate hydroxide pastes that applying mechanical excitation by means of vibration or flow of the paste the emerging desiccation crack pattern remembers the direction of excitation [6,7]: for vibration and flow the primary crack orientation becomes perpendicular and parallel to the direction of excitation, respectively. Detailed experiments varying the way of excitation, furthermore, the strength and range of interaction of colloidal particles have * ferenc.kun@science.unideb.hu revealed that the memory effect of pastes provides an efficient way of controlled generation of crack patterns in thin layers.…”