| Abstract: |
When a toothpick coated with a surfactant is inserted into a thin film of Japanese ink (sumi) floating on a water surface, the film ruptures, and a beautiful star-shaped pattern spontaneously forms. This phenomenon is known as "Sumi-wari". These star-shaped patterns on the water surface are often transferred onto washi paper or fabric, representing one of Japan’s traditional dyeing techniques. While a paper on the science of Sumi-wari was published by Torahiko Terada approximately 100 years ago, there have been no subsequent reports on the subject until now. In this study, we treat Sumi-wari as a fracture phenomenon of soft matter, investigating it through experiments and mathematical modeling using modern scientific techniques. In this presentation, we will discuss the physical mechanisms of Sumi-wari as a soft matter fracture process based on our experimental results and theoretical models. This research is collaborated with L. Pauchard (FAST), L. Goehring (Nottingham Trent Univ.), A. Kinoshita (Nara Women's Univ.) and H. Sakaguchi (Nihon Univ.).
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