Memory effect of paste and its visualization as desiccation crack patterns
Akio Nakahara, Nihon University, Japan

A densely packed colloidal suspension, called a paste, remembers the direction of external forces, such as vibration, flow and magnetic field, even after the external field is removed, and these memories in paste can be visualized as morphology of crack patterns which appear in a drying process. When a paste remembers the direction of vibration, desiccation cracks run in the direction perpendicular to the initial vibration, while desiccation cracks run along the direction of initial flow or magnetic field when the paste remembers the direction of flow or magnetic field [1]. Recently we have succeeded in controlling the position of crack formation by localizing the region of strong horizontal vibration at nodes of Faraday waves [2]. Our next challenge is to erase the memory in paste to increase the breaking strength of the material and its progress will be shown in the talk.

[1] Desiccation Cracks and their Patterns: Formation and Modelling in Science and Nature, Lucas Goehring, Akio Nakahara, Tapati Dutta, So Kitsunezaki, and Sujata Tarafdar (Wiley, 2015) .
[2] H. Nakayama, Y. Matsuo, Ooshida T. and A. Nakahara, "Position control of desiccation cracks by memory effect and Faraday waves", European Physical Journal E 36 (2013) 1.

seminar schedule