arXiv subjects

Dixi Yang

Publications and source records attributed to Dixi Yang.

2 recordsLinked to original sources

arXiv2026

Wetting-coupled phase separation as an energetic mechanism for active bacterial adhesion

The rapid adhesion of motile bacteria from dilute suspensions poses a fundamental non-equilibrium problem: hydrodynamic interactions bias bacterial motion near surfaces without generating stable confinement, while electrostatic interactions are predominantly repulsive. Here, combining experiments on Pseudomonas aeruginosa and Staphylococcus aureus in a polyethylene glycol/dextran aqueous two-phase system with large-scale hydrodynamic simulations, we identify wetting-coupled liquid--liquid phase separation (LLPS) as an energetic trapping mechanism for bacterial adhesion. When bacteria partition into a phase that preferentially wets the substrate, interfacial free-energy minimization creates a deep energetic trap that stabilizes adhesion and induces lateral clustering via capillary interactions. Crucially, bacterial motility plays a dual role: at low phase volume fractions, activity enhances transport into the wetting layer and promotes accumulation, whereas at higher phase volumes it suppresses adhesion through the formation of self-spinning droplets that generate hydrodynamic lift opposing interfacial trapping. Our results establish wetting-coupled LLPS as a generic physical route governing interfacial organization in active suspensions. This provides a unified energetic framework for bacterial adhesion in complex fluids, with broad implications for deciphering bacterial-cell interactions and controlling biofilm formation.

cond-mat.soft↗

arXiv2025

Active motility and wetting cooperatively regulate liquid-liquid phase separation

Liquid--liquid phase separation in aqueous two-phase systems is fundamental across physical and biological sciences. While well understood for passive mixtures, how it is regulated by active agents such as motile bacteria remains largely unexplored. By combining experiments on Pseudomonas aeruginosa in a dextran--polyethylene glycol mixture with hydrodynamic simulations, we show that the coupling between bacterial activity and interfacial wetting converts self-propulsion into mechanically effective interfacial stresses, giving rise to a robust sequence of morphologies, including self-spinning droplets, elongated droplet chains, and branched capillary-like clusters. More importantly, it gives activity a dual kinetic role: activity suppresses coarsening in the droplet regime through rotation-induced hydrodynamic repulsion, but accelerates coarsening when dextran is the minority phase, where wetting-mediated attraction drives aggregation. To probe the biological relevance of this mechanism, we further show that a biofilm-associated protein can act as an interfacial ``wetting glue,'' promoting bacterial clustering even in dilute suspensions. Our findings establish activity--wetting coupling, rather than activity or wetting alone, as a mechanism by which active motility regulates pattern morphology and coarsening dynamics, and reveal a physical route to enhancing bacterial aggregation from dilute suspensions.

cond-mat.soft↗