Reshaping soft colloidal gels using synthetic active particles

• Applicant: Alexander Petrunin
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics ; Preparatory and Physical Chemistry of Polymers
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576130641

Self-propelling particles mimic the behaviour of motile bacteria and, in stark contrast to systems in thermodynamic equilibrium, exhibit complex mutual interactions with their surroundings. Understanding this coupling is crucial to describe the bacterial dynamics in their natural environment, which is typically soft (e.g. soil or human body), and develop medical microrobots or self-healing dynamic materials. Here, we propose to study the coupling between the swimming of catalytic active microparticles and colloidal gels with tunable softness. We will realize colloidal gels both in two and three dimensions using swollen polymer particles of varying softness, dope these gels with active colloids and follow the self-propelling motion of the active colloids. Simultaneously, we will record the changes in viscoelasticity and microstructure of the gels due to this motion. We foresee that in ‘hard’ gels the active colloids will swim in the available free volume and reorient more often, whereas microstructure of the gel will not change significantly. Conversely, in ‘soft’ gels the active colloids will experience higher velocity fluctuations, as they break and re-shape the network; the microstructure and viscoelasticity of the gels will be strongly affected, resulting in weaker structures. We will highlight the fundamental differences between two- and three-dimensional gels due to the different degrees of freedom and impact of gravity.

• DFG Programme: WBP Position