PhD defence

Emergent Mixing or De-mixing in Heterogeneous Colloidal Flocks

• S. Maity

Date

Friday 16 October 2026

Time

10:00 - 11:00 hour

Address

Academy Building
Rapenburg 73
2311 GJ Leiden

Supervisor(s)

• Prof.dr. M.L. van Hecke
• dr. A. Morin

Summary

Birds fly in a flock, cattle move in herds, fish swim in a school, and humans gather in crowds to celebrate, commute, or protest. Within all these active collectives, each individual is unique, making such aggregations inherently heterogeneous.

This work investigates how such individual variability or heterogeneity shapes their collective motion, using a model experimental system prepared from a binary flock of microscopic, spherical particles. These binary flocks either spontaneously segregate or remain homogeneously mixed under different physical constraints, which we further explain using a multicomponent hydrodynamic model.

Thus, we uncover the laws that govern spatial self-organization in such complex systems, providing broader insights into how individual heterogeneity can drive emergent collective behavior.

PhD dissertations

Approximately one week after the defence, PhD dissertations by Leiden PhD students are available digitally through the Leiden Repository, that offers free access to these PhD dissertations. Please note that in some cases a dissertation may be under embargo temporarily and access to its full-text version will only be granted later.

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