Impact of softness of individual colloids on the shear banding in soft glassy materials

We will understand the role of the softness of an individual colloid on the structuring and macroscopic properties of a suspension under flow.

Suspensions of microgels (soft deformable colloids) will be studied by combining small-angle x-ray and neutron scattering to probe both the particle-to-particle arrangement and the shape of the individual colloid.

We will design, develop, and realise two shear cells, one to probe small-angle scattering (SAS) in the flow-plane, the optimal plane to observe deformations of a material, and the second to probe high applied shear (>104 s-1). The cells will enable simultaneous polarised microscopy, rheology and SAS experiments.

Microgel suspensions are a textbook example of complex fluids showing fluid-to-crystal transitions, shear thinning, shear banding and the possibility to form glasses or jammed systems.

These phenomena are common to most soft materials, both synthetic and bio-relevant, such as protein suspensions, saliva, and blood.

SAS experiments in the flow plane and at unprecedently high shear rates will allow us to identify the key parameters in the softness of a colloidal particle that affect the flow properties of the suspension.

The knowledge developed in this project will pave the way to the design of soft colloids for bio-medical applications, emulsion-stabilized formulations of cosmetics, detergents and shampoos.