CECAM Workshop: Rheology of gel networks: combining experimental, computational and theoretical insights

Aim of the workshop

The idea of this workshop is to bring together international experts in the field of the dynamics of gel networks, to discuss recent progress and insight from computational, theoretical and experimental approaches. This field is very young especially concerning modeling aspects, due to the computational challenges related to the complex molecular structures which are crucial, in many cases, for relaxation dynamics and mechanical responses on large scales.

In the recent years, however, the computer power and new parallel coding techniques like GPGPU or large scale MPI programming techniques has allowed for significant progress in accessing reasonable time and length scales to address questions that were difficult to tackle before. Also on the experimental side, new approaches combining different techniques (e.g. various types of spectroscopy and rheology) allow for an investigation on a more mesoscopic scale of the complex dynamics, being able to probe scales that can be modeled within, for example, MD simulations. In addition, recent theoretical developments now address specifically the non-linear response of soft materials, providing new concepts and ideas to be tested in experiments and simulations. There seems to be a unique opportunity, at this point, in combining such efforts to develop a new understanding of gels, closely related to their technological applications.

Specific topics

The specific topics and questions that we would like to focus on are the following:

Aging and Relaxation: Time evolution of structure and material properties; stretched and compressed exponential relaxation; elastic effects.
Structural Heterogeneities, Coarsening and Restructuring: Role of coarsening dynamics in phase separating suspensions and mixtures; changes of the structure upon forcing or relaxation; interplay between structural and stress heterogeneities.
Gel Rheology at Small and Large Amplitude Deformations: Specificity of the rheology of networks with respect to dense systems; connection between the linear and non-linear response of gels and their microstructure; fatigue and rheological hysteresis in terms of damage accumulation in soft amorphous solids.
Rigidity Percolation, Soft Modes and Stressed States: Onset of mechanical stability and rigidity percolation; role of frozen-in stresses in the gel structures; marginality and soft modes in disordered networks related to frozen in stresses; specific caracter of non-affine rearrangement.
Creep and Precursors to Failure: Critical slowing down of dynamics as stress decreases and related scaling laws; microstructural origins of the creep; possibility to define precursors; materials durability.
Design and Control of Mechanical Instabilities: Hardening, stress and strain localization; controlling structural damage; coupling between the emergence of strongly non-linear response and specifically designed structural/micromechanical features; role of walls and confinement under deformation.

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