Embedding orthogonal memories in a colloidal gel through oscillatory shear

Area of Science:

• Soft Matter Physics
• Materials Science
• Rheology

Background:

• Disordered systems can store memories of applied shear protocols in physical parameters like yield strain.
• Oscillatory shear training is a method to modify and recall these material properties.

Purpose of the Study:

• To investigate shear training memories in colloidal gels, focusing on their network structure and attractive interactions.
• To determine if colloidal gels can store memories along and orthogonal to the training flow direction.

Main Methods:

• Utilized oscillatory shear protocols to set and read out yield strain memories.
• Employed confocal microscopy to analyze the evolving gel structure during shear training.
• Examined the isotropy of gel bonds in the shear-vorticity plane.

Main Results:

• Colloidal gels exhibit shear training memories in both the direction of the training flow and orthogonal to it.
• Gel bonds largely maintained an isotropic structure in the shear-vorticity plane during training.
• Structures developed for shear along one direction also supported shear along the orthogonal direction.

Conclusions:

• Colloidal gels possess memory capabilities extending beyond the training flow direction, demonstrating orthogonal memory.
• This orthogonal memory enhances the utility of shear training for diverse applications in disordered systems.
• The findings suggest broad applicability to other disordered materials exhibiting network structures.