Effect of Interaction on the Formation of Memories in Paste

TL;DR

This study investigates how adding salt to colloidal paste influences its ability to remember flow directions, revealing that salt screening of electrostatic interactions enables memory formation.

Contribution

It demonstrates that salt addition modifies the memory effect in colloidal paste by screening Coulombic repulsion, allowing controlled tuning of crack pattern morphology.

Findings

Salt addition enables paste to remember flow direction.

Screening electrostatic interactions induces memory formation.

Crack pattern morphology can be precisely tuned with salt.

Abstract

A densely packed colloidal suspension with plasticity, called paste, is known to remember directions of vibration and flow. These memories in paste can be visualized by the morphology of desiccation crack patterns. Here, we find that paste made of charged colloidal particles cannot remember flow direction. If we add sodium chloride into such paste to screen the Coulombic repulsive interaction between particles, the paste comes to remember flow direction. That is, one drop of salt water changes memory effect in the paste and thereby we can tune the morphology of desiccation crack patterns more precisely.