Active matter

Active matter refers to collective, ordered states of matter in ensembles of particles with intrinsic motion and alignment interactions. Examples span biological systems, like bird flocks and bacterial swarms, down to cellular tissues and subcellular systems, e.g. cytoskeletal filaments. These active systems exhibit large-scale orientational ordering in analogy with liquid crystals of different discrete rotational symmetries (polar, nematic, triatic..). At sufficiently high activity, the orientational order is locally punctuated by the spontaneous nucleation of topological defects which induce long-range elastic distortions and persistent flows.

Spontaneous flows in active liquid crystals

We study the spontaneous active flows induced by topological defects in thin active films with nematic or polar order. Using hydrodynamic models of active liquid crystals, we investigate the effect of incompressibility constraint, the role of hydrodynamic screening length and inhomogeneous activity on the flow profiles and defect dynamics.

PhD project of Jonas Rønning - PhD thesis (2023)

Spontaneous active flow induced by a -1/2 defect (left panel) and a + 1/2 defect (right panel) — Spontaneous active flow induced by a -1/2 defect (left panel) and by a + 1/2 defect (right panel) (by J. Rønning

Spontaneous active flow induced by -1 defect (left panel) and by a +1 defect (right panel) by J. Rønning

T1 transitions in confluent tissue monolayers

We use multi-phase field model simulations to study collective dynamics of cell and tissue flows in confluent monolayers.

PhD project of Harish P. Jain - part of the CompSci Doctoral Program

Image may contain: Colorfulness, Line, Pattern, Symmetry, Creative arts. — T1 transition event (top panels). Collective cell migration due to chaining of T1 transitions. by H. Jain

Tissue morphogenesis

We develop a discrete model for aggregates of cells interacting through their cell polarities study the interplay between flow, topology and geometry during the early tissue morphogenetic processes.

We have shown that a tubular structure can develop spontaneously at a vortex location and in the presence tissue fluidisation.

By Richard Ho — Spontaneous tube formation. By Richard D.J.G. Ho.

This work is done with Richard D. J.G. Ho and is part of the ITOM Convergence Environment at UiO: Life Sciences.

Published July 25, 2023 2:52 PM - Last modified Nov. 12, 2025 12:02 AM