Capillary force-driven particle orientation in rod networks

Abstract

Hypothesis: Anisotropic rod particles in capillary suspensions form complex network structures with distinctive orientation patterns and rheological properties that differ significantly from spherical particle systems. By identifying the orientation of individual particles, we are able to acquire invaluable experimental insight into the bulk particle orientation measurements. Experiments: Glass microrods were dispersed in capillary suspensions with varied secondary liquid volume fractions. The resulting microstructural characteristics were analyzed using confocal microscopy. Meanwhile, their rheological properties were measured through rheometry and rheoconfocal techniques. Particle networks were quantified in terms of coordination number, clustering coefficient, and orientation distribution. Findings: As the secondary liquid volume fraction increased, rod networks transitioned from point-to-point contact configurations to side-to-side aligned clusters. Unlike spherical systems, the average clustering coefficient decreased with increasing coordination number, indicating the formation of complex particle cluster configurations beyond simple side-to-side alignment. The rod networks demonstrated higher sensitivity to deformation, and samples with higher side-to-side contact probability exhibit higher viscoplastic fragility. These results provide a foundation for designing advanced materials with precisely tunable mechanical properties through controlled anisotropic particle interactions in capillary suspensions.