Embedding Orthogonal Memories in a Colloidal Gel through Oscillatory Shear

TL;DR

This study demonstrates that colloidal gels can embed and support orthogonal shear memories through oscillatory shear training, revealing isotropic structural rearrangements that extend the potential applications of shear memory effects.

Contribution

It introduces the concept of orthogonal shear memories in colloidal gels and shows their structural basis using confocal microscopy, expanding understanding of memory effects in disordered systems.

Findings

Colloidal gels support shear memories along and orthogonal to training flow.

Gel structures remain largely isotropic in the shear-vorticity plane.

Orthogonal memories enhance the applicability of shear memory techniques.

Abstract

It has recently been shown that in a broad class of disordered systems oscillatory shear training can embed memories of specific shear protocols in relevant physical parameters such as the yield strain. These shear protocols can be used to change the physical properties of the system and memories of the protocol can later be "read" out. Here we investigate shear training memories in colloidal gels, which include an attractive interaction and network structure, and discover that such systems can support memories both along and orthogonal to the training flow direction. We use oscillatory shear protocols to set and read out the yield strain memories and confocal microscopy to analyze the rearranging gel structure throughout the shear training. We find that the gel bonds remain largely isotropic in the shear-vorticity plane throughout the training suggesting that structures formed to support shear along the training shear plane are also able to support shear along the orthogonal plane. Orthogonal memory extends the usefulness of shear memories to more applications and should apply to many other disordered systems as well.