  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
from fiber looks like a Chinese pagoda, we name this instability as pagoda
instability (PI). Coupling of dissolution and wetting leads to other special
phenomena, i.e. dissolving-induced jet flow, and optimizes the fiber shape,
etc. We propose a criterion of PI and show the competition between interface
energy and chemical potential deduce the MCL motion and PI. A phase diagram is
used to summary the final shapes of fibers. By conducting atomic force
microscope (AFM) measurement, we find the fiber with optimized-shape has the
characteristics of low adhesion force. Using the optimized-fiber can decrease
the 70% influence of capillary force for AFM measurement in humid environment.
