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%.