Quanzi Yuan | Searcharxiv

arXiv2020

The pagoda instability (PI) on soluble fibers

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.

physics.chem-ph↗

arXiv2017

Topography-induced symmetry transition of droplets on quasi-periodically patterned surfaces

Quasi-periodic structures of quasicrystals yield novel effects in diverse systems. However, there is little investigation on employing quasi-periodic structures in the morphology control. Here, we show the use of quasi-periodic surface structures in controlling the transition of liquid droplets. Although surface structures seem random-like, we find that on these surfaces, droplets spread to well-defined 5-fold symmetric shapes and the symmetry of droplet shapes spontaneously restore during spreading, hitherto unreported in the morphology control of droplets. To obtain physical insights into these symmetry transitions, we conduct energy analysis and perform systematic experiments by varying properties of both liquid droplet and patterned surface. The results show the dominant factors in determining droplet shapes to be surface topography and the self-similarity of the surface structure. Our findings significantly advance the control capability of the droplet morphology. Such a quasi-periodic patterning strategy can offer a new method to achieve complex patterns.

physics.app-ph↗