Laurent Blanchoin | Searcharxiv

arXiv2026

Phase separation by polar active transport

We propose an active Cahn-Hilliard theory for the dynamics of a new type of phase transition where the driving force is not the direct interactions between the two separating components, but their active sorting by a third polar species. This third species can transport the other two along its polarity in opposite directions, thus separating them. Inspired by recent experiments where molecular motors that walk in opposite directions along microtubules are sorted into separated domains, our theoretical description of this process introduces a new mechanism for active phase separation and could serve as a model for the organization of biological material in space inside cells. We predict the formation of motor domains, and further show that they can either coarsen to form macroscopic phases or reach a finite micro- or mesoscopic steady state size, these latter due to an arrest of coarsening through activity.

cond-mat.soft↗

arXiv2025

Gliding microtubules exhibit tunable collective rotation driven by chiral active forces

How chirality propagates across scales remains an open question in many biological and synthetic systems. An especially clear manifestation of this propagation is found in in vitro gliding assays of cytoskeletal filaments on surfaces, driven by molecular motors. These assays have become model systems of active matter dynamics, as they spontaneously organize into diverse dynamical states, including collective motions with chiral rotation. However, the microscopic mechanisms underlying these chiral collective dynamics have remained unclear. Here, we investigate rotating active nematic order in microtubule gliding assay experiments under two stabilization conditions, each on two types of substrates. We propose that chirality in active forces exerted by motors on microtubules represents a viable mechanism for this large-scale chirality. Using Brownian dynamics simulations of self-propelled, semiflexible filaments with chiral activity, we demonstrate that coherently rotating active nematic order emerges by this mechanism even in the absence of curvature, i.e. shape chirality, of the constituent filaments. Moreover, we predict that the angular speed and handedness of the collective rotation can be tuned by modulating filament stiffness. Our findings identify a new set of sufficient microscopic ingredients for predictable propagation of chiral handedness from the molecular to the material scale in living and active matter.

cond-mat.soft↗