arXiv abstract link

A new study led by researchers from Ben-Gurion University of the Negev (BGU) reveals that living matter violates previously known physical principles of symmetry when cellular flows form and break dow...

arXiv abstract link

arXiv abstract link

Proceedings of the National Academy of Sciences, Volume 123, Issue 36, September 2026. SignificanceThe equilibrium polar patterns and their dynamics under external torques are of general interest in the field of ferroic materials. Among them, ferroelectric nematics exhibit novel behaviors because they combine spontaneous polarization and ...

Regulation of topological structures and pattern formation is attracting wide interest in the field of condensed matter. Liquid crystals (LCs) represent soft matter with a remarkable combination of fluidity and anisotropic properties. Topological defects may appear in confined LCs under external stimuli. Recently discovered ferroelectric nematics (NF) opened exceptional opportunities in technologies owing to high permittivity and polarisation. Polar properties of NF supply more variability to topological structures. In this research, we present tunable 2D topological defect arrays in NF compound, induced by an alternating (AC) electric field in simple sandwich cells without pre-patterning. The observed arrays of defects form pseudo-square lattices, which character and periodicity depend on the frequency of the applied field and partially on the cell thickness. The observed effect is explained to occur due to the competition between elastic and electrical forces. The proposed system can be useful to create reconfigurable spatially periodic polarisation structures.

Living systems are composed of discrete units, assembled through a hierarchy of structures, and active, by locally extracting energy from their environment to produce mechanical work. Hydrodynamic theories have been successfully applied to describe the large scale dynamics of active materials. Yet, the hydrodynamic limit requires a separation of scales which is not necessarily fulfilled among living systems. In this work, we propose a novel agent-based model of flexible rods exchanging active force dipoles with nematic symmetry, allowing us to explore their behavior down to the sub-agent scale. We obtain spontaneous flows and self-propulsion of $+1/2$ topological defects, hallmarks of the hydrodynamic theory of active nematics, even on scales smaller than the individual agent! Moreover, our results go beyond the hydrodynamic framework, identifying novel correlations between orientation and flows or strong asymmetries between contractile and extensile activity. Finally, we show the versatility of our agent-based model by presenting spontaneous flows in three dimensions and nematic tissue growth. Because living systems like cell tissues often exhibit several sources of activity, our framework opens the way for more integrated descriptions of living materials.

Living systems are composed of discrete units, assembled through a hierarchy of structures, and active, by locally extracting energy from their environment to produce mechanical work. Hydrodynamic theories have been successfully applied to describe the large scale dynamics of active materials. Yet, the hydrodynamic limit requires a separation of scales which is not necessarily fulfilled among living systems. In this work, we propose a novel agent-based model of flexible rods exchanging active force dipoles with nematic symmetry, allowing us to explore their behavior down to the sub-agent scale. We obtain spontaneous flows and self-propulsion of $+1/2$ topological defects, hallmarks of the hydrodynamic theory of active nematics, even on scales smaller than the individual agent! Moreover, our results go beyond the hydrodynamic framework, identifying novel correlations between orientation and flows or strong asymmetries between contractile and extensile activity. Finally, we show the versatility of our agent-based model by presenting spontaneous flows in three dimensions and nematic tissue growth. Because living systems like cell tissues often exhibit several sources of activity, our framework opens the way for more integrated descriptions of living materials.

Epithelial cells can resemble nematic liquid crystals, exhibiting long-range alignment and topological defects. Bera et al. show that these defects do not arise randomly but that they are pre-patterned by coordinated cell forces and motions. Some of these defects can move in both directions within the same tissue, driven by distinct distributions of cell-generated traction forces and internal stresses.