Simplified Industrial Formulations of Colloidal Dispersions: Design Challenges

First, this work provides a unified framework for designing tougher and more processable
colloidal gels by tuning particle surface chemistry, roughness, and shape. We developed
a reproducible thermoreversible model system using octadecyl-grafted silica particles in
tetradecane, enabling precise control of grafting density and gelation temperature. Modeling
and AFM measurements show that temperature-dependent interactions between
grafted chains, rather than van der Waals forces, govern reversible gel formation.
Using this platform, we demonstrate how aspect ratio and surface roughness jointly determine
network architecture and mechanics: roughness lowers the percolation threshold
and improves stability, while elongated particles strengthen elasticity and yield behavior.
Combining both yields homogeneous, shear-resistant networks. These insights offer
practical design rules for tailoring flow, stability, and recovery in next-generation soft
materials and formulations.

Second, We directly image the microscopic dynamics of colloidal gels under shear and
show that yielding is triggered by rare, collective, near-critical plastic rearrangements
at the particle scale. By isolating these events through a robust nonaffine-displacement
framework, we establish the microscopic origin of the elastic–plastic transition and create
a foundation for microstructure-based constitutive models for thixotropic soft solids.
Building on these insights, we developed and validated elasto-visco-plastic models for
simple yield-stress fluids. A scalar version, reducing to a modified Maxwell model, accurately
predicts complex protocols such as LAOS, while its tensorial extension captures
the coupling between 3D stress components. Both models reproduce complex deformation
behavior and the interplay of elastic and dissipative responses.

Third, new micro-mechanical tools (rheo-confocal imaging and optical tweezers on model
aggregates) directly link bond- and node-level mechanics to macroscopic properties. In
particular, surface roughness extends the linear deformation regime and alters yielding
modes.