Evaporation of Drops on Two Parallel Fibers: Influence of the Liquid Morphology and Fiber Elasticity

Abstract

We investigate experimentally the evaporation of liquid accumulated on a pair of parallel fibers, rigid or flexible. The liquid wetting the fibers can adopt two distinct morphologies: a compact drop shape, whose evaporation dynamics is similar to that of an isolated aerosol droplet, or a long liquid column of constant cross-section, whose evaporation dynamics depends upon the aspect ratio of the column. We thus find that the evaporation rate is constant for drops, while it increases strongly for columns as the interfiber distance decreases, and we propose a model to explain this behavior. When the fibers are flexible, the transition from drops to columns can be induced by the deformation of the fibers because of the capillary forces applied by the drop. Thus, we find that the evaporation rate increases with increasing flexibility. Furthermore, complex morphology transitions occur upon drying, which results in spreading of the drop as it evaporates.

Capillary Force‐Driven, Hierarchical Co‐Assembly of Dandelion‐Like Peptide Microstructures

“…In this system, two key issues needed to be addressed at different stages of the co‐assembly process. First, uniform FF microtubes must be synthesized with the desired flexibility; flexibility is closely related to fiber geometry (i.e., the diameter and wall thickness of the FF microtubes, crucial parameters affecting the wetting and drying of drops on parallel fibers) . Second, the assembly order of the FF and Fc‐FF peptides must be controllable under the same conditions.…”

“…For this work, the inspiration to program such complex peptide microstructures arose from a very simple physical phenomenon – the wetting and drying of flexible fiber arrays. Despite their ubiquity in both natural and engineered systems, comprehensive and visual studies of such processes were not reported until recently . Based on these recent findings, we deposited a tiny drop of Fc‐FF solution on a pair of parallel fibers and observed that Fc‐FF solutes accumulate at the free ends of these fibers due to capillary forces.…”

“…Recently, Stone and co-workers undertook a comprehensive investigation of the wetting and drying of liquid drops on fl exible fi bers, a common physical process in both natural and industrial applications. [22][23][24] To simplify the physical model, they used drops of silicone oil, a perfectly wetting liquid that does not contain any solutes. However, the wetting and drying phenomena for drops of solutions containing self-assembling peptides are not well understood.…”

“…Wetting–drying phenomena abound in nature (e.g., the “coffee ring” effect, tears of wine, wetting of fibers . The capillary forces underlying these phenomena could be used to control hierarchical self‐assembly processes.…”

“…Wetting-drying phenomena abound in nature (e.g., the "coffee ring" effect, [ 20 ] tears of wine, [ 21 ] wetting of fi bers. [22][23][24] The capillary forces underlying these phenomena could be used to control hierarchical self-assembly processes. For instance, using the "coffee ring" effect as inspiration, Lin and co-workers rationally designed a series of geometric modules to precisely control the self-assembly of nanoparticles, polymers, or DNA strands into periodic patterns on surfaces.…”