3D aggregation of wet fibers

Wet fibrous structures such as nanotube carpets or macroscopic brushes tend to self-assemble into bundles when the liquid evaporates. The aggregation process relies on a balance between capillary attraction provided by liquid bridges and restoring torque due to structure stiffness. The final self-organized structure is found to result from a cascade of pairing of smaller bundles into bigger ones. We first describe, both experimentally at a macroscopic scale and theoretically, the case of a single pair of fibers and then generalize this description to more complex 3D assemblies. We finally show the relevance of our results to micro-scale experiments from the literature.