Memories of paste

Overview

References:

• Weitz, D., Nature 410, 32-33 (2001).

In his article, Weitz primarily describes the following paper:

• Cloitre, M., Borrega, R. & Leibler, L. Phys. Rev. Lett. 85, 4819-4822 (2000).

Key Words: Paste, Glass, Microgel, Stress, Relaxation, Ageing

Summary

Weitz's article draws attention to the findings of Cloitre, Borrega, and Leibler and goes on to list related questions for future exploration.

Cloitre, Borrega, and Leibler studied the rheology of a paste consisting of pieces of microgel suspended in a fluid.

The related questions Weitz lists are:

• 1) What causes the ageing affect?
• 2) How much impact does the surprising rheology have?
• 3) Is the ageing affect specific to the particular microgel paste, or does it apply to other pastes or even other kinds of soft matter?

Soft Matter Details

Types of Soft Matter

As the title suggests, Memories of Paste focuses primarily on a class of soft materials called pastes. However, the author remarks on a similarity between pastes, gels, and glasses. "...the way a paste recovers from an applied stress is remarkably like the behaviour of glasses and gels." (p.32)

• What is the difference between a paste, a gel, and a colloid?

• • "Pastes typically consist of a suspension of small particles in a background fluid. These particles are crowded, or jammed together like grains of sand on a beach, forming a disordered, glassy, or amorphous structure." (p.32)

The property of the specific microgel paste highlighted in this article is a stress-relaxation aging relationship.

Experimental Methods

author: Becca Perry