Wetting morphologies on randomly oriented fibers

Abstract

We characterize the different morphologies adopted by a drop of liquid placed on two randomly oriented fibers, which is a first step toward understanding the wetting of fibrous networks. The present work reviews previous modeling for parallel and touching crossed fibers and extends it to an arbitrary orientation of the fibers characterized by the tilting angle and the minimum spacing distance. Depending on the volume of liquid, the spacing distance between fibers and the angle between the fibers, we highlight that the liquid can adopt three different equilibrium morphologies: 1) a column morphology in which the liquid spreads between the fibers, 2) a mixed morphology where a drop grows at one end of the column or 3) a single drop located at the node. We capture the different morphologies observed using an analytical model that predicts the equilibrium configuration of the liquid based on the geometry of the fibers and the volume of liquid.

Drop morphologies on flexible fibers: influence of elastocapillary effects

“…Above this angle, we recover the morphology diagram of the rigid fibers as the capillary force is not sufficient to significantly bend the fibers at large tilting angle δ. Indeed, the column/mixed morphology transition described by Sauret et al [28] for rigid fibers satisfactorily captures the column/mixed morphology transition for flexible fibers as reported in Fig. 2(f).…”

“…Note that the value at which the bending of the fibers becomes important depends on the flexibility of the fibers and thus on the elastocapillary length compared to the fibers length. Therefore, the transition between the different regimes can be described by the model developed for rigid fibers, and described in previous publications [48,28].…”

Continuous and discontinuous transitions between two types of capillary bridges on a beaded chain pulled out from a liquid

“…Therefore, a great effort is made to understand the mechanisms of their formation and shape development, [29][30][31] rupturing [32][33][34][35] and evaporation. 36,37 Capillary bridges exist at solid contacts between spheres, [38][39][40] rods, [41][42][43] plates, 44,45 a mix of these, [46][47][48][49] or other shapes. 50,51 They are also formed, when a particle is being pulled out from a suspension.…”

10.1063/1.4935251.1

“…However, the reentrainment of water in the air and the clogging of the fiber network then represents the major limitations to the improvement of the net's efficiency [3]. Indeed, when liquid collects on an array of fibers, the drops can attain a stable configuration between the fibers [4,5,6], preventing liquid collection and decreasing the efficiency of such a net. To optimize the design and the efficiency of fog nets, three-dimensional hierarchical structures have been proposed [7,8], which can be coupled with chemical surface properties of the material to alter the contact angle hysteresis [3].…”

“…(b) Critical radius after which the drop detaches from the fiber versus the local amplitude a of the fiber. The solid line is equation(6).…”