Elastocapillarity: stress transfer through fibrous probes in wicking experiments

Current advances in the manufacture of nanoporous and nanofibrous materials with high absorption capacity open up new opportunities for the development of fiber-based probes and sensors. Pore structures of these materials can be designed to provide high suction pressure and fast wicking. During wicking, due to the strong capillary action, liquids exert stresses on the fiber network. In this paper, we discuss the effect of stress transfer in the direction of propagation of the wetting front. As an illustration, we first consider a single capillary and demonstrate the effect of a moving meniscus on stress distribution along capillary walls. We then analyze similar effects in yarns. We consider a yarn that can capture an aerosol droplet as a promising sensing element that could monitor the stresses caused by wetting fronts. We also discuss the elastocapillary effects occurring during upward and downward wicking. The distributions of stresses in these two cases are shown to differ significantly. We discuss how these effects might be exploited for designing fiber-based sensors that can probe very small amounts of liquids.