Moving Contact Line Instability on Soluble Fibers

Abstract

This paper presents a new kind of instability when inserting a soluble fiber into liquid. After wetting and dissolving the fiber by the liquid, the moving contact line (MCL) spontaneously loses stability. Because the sculpted shape of the fiber looks like a Chinese pagoda, this instability is named as the pagoda instability (PI). The coupling of dissolution and wetting leads to other special phenomena, i.e., dissolving‐induced jet flow, and optimizes the fiber shape, etc. A criterion of PI is proposed and the competition between the interfacial energy and chemical potential to deduce the MCL motion and PI is shown. A phase diagram is used to summarize the final shapes of the fibers. By conducting atomic force microscopy (AFM) measurements, it is found that fibers with optimized shapes have a low adhesion force. Using the optimized fiber can decrease the influence of the capillary force during AFM measurements in humid environments by 70%.

Shape optimization of a meniscus-adherent nanotip

“…19,21,50 Therefore, accurately judging the optimized shape is of great significance. It is noteworthy that the tip apex curvature radius cannot be infinitesimal, but that theoretical works 16–18 assume the apex to be infinitely sharp.…”

“…Furthermore, an optimized tip can be cut and glued to an AFM probe, preventing adhesion of the liquid. 17 Therefore, the special shape of an optimized tip reduces the capillary effect.…”

“…[28][29][30] Elegant molecular simulations have also studied the capillary adhesion of nanotips. [31][32][33] The capillary force of a meniscus can significantly reduce the imaging quality or measurement accuracy; 17,34 Hence, a tip that could reduce the capillary force is preferred.…”

“…Besides, theoretical research on tips is based on continuum theory, in which many assumptions are made to simplify calculations. 16–18 Some of these assumptions are not fully applicable to atomic-scale tip-shape evolution. In the context of these challenges, atomistic modelling serves as a powerful probe to elucidate tip formation mechanisms.…”

From the teapot effect to tap-triggered self-wetting: a 3D self-driving sieve for whole blood filtration

“…For example, Yang et al reported chemicalmechanical capillarity to design and generate an optimized shape, which made liquids slide off the surface very quickly. Similarly, we may shape the 3D sieve to follow the brachistochrone curve in our future study and further improve the filtration performance 39 .…”