Control of Spatial Periodicities of Dewetting Structures of Oleo-Liquid Films

Fabrication of Spatially Periodic Double Roughness Structures by Directional Viscous Fingering and Spinodal Dewetting for Water-Repellent Surfaces

“…All of the samples before the water processing possessed almost the same water-repellent properties as the flat surface shown in Figure 10, indicating that the mesoscopic stripe pattern alone cannot enhance the water-repellent properties. In addition, every sample on which only a microscopic dewetting pattern was formed as prepared in our previous report 46 did not show any strong water-repellent properties, indicating that the microscopic dewetting pattern alone cannot enhance the water-repellent properties. The water processing did not influence the water-repellent properties of the samples coated by setting the gap of the applicator at 12.7 µm, since no surface structural change was generated by the water processing.…”

“…In our previous study, the plate on which the liquid film was formed was immersed in stationary water at 35 °C for 10 min. 46 In order to speed up the formation of the dewetting patterns, the water processing was carried out by immersing the plate into a 35 °C water shower flowing at 4 L‚min -1 for 1 min. Examples of FE-SEM images of the surface before and after the water processing are shown in Figure 9.…”

“…The liquid film having a weight ratio of OSI-TIO2-35/OPMC ) 7:3 underwent dewetting when the film weight was 0.100 mg‚cm -1 but not when it was 0.200 mg‚cm -1 . 46 Since the density of the suspension is 1.67 g‚cm -3 , the film thickness corresponded to 0.60 and 1.20 µm, respectively. In the case of the liquid film prepared by setting the gap of the applicator at 12.7 µm, the minimum liquid film thickness, 1.50 µm, was realized at the bottom part of the stripe pattern as shown in Figure 6.…”

“…We recently analyzed the dewetting pattern formation of liquid films containing octyl p-methoxycinnamate (OPMC) and an octylsilyl titanium dioxide particle having an average diameter of 35 nm (OSI-TIO2-35) on a glass plate. 46 In this study, a suspension of OSI-TIO2-35 in volatile silicone, decamethyl cyclopentasiloxane (DMCPSI), was mixed with OPMC, and the mixture was spread on a glass plate by dragging an applicator using a linear motor coater. Spatially periodic stripe patterns were formed spontaneously in some cases by the directional viscous fingering.…”

Preparation of Highly Water-repellent Surface by Spontaneous Formation of Double Scale Roughness Pattern

“…Formation of spatially periodic single scale stripe patterns by the directional viscous fingering alone, however, did not change the water-repellent property of the surface. Additional microscopic dewetting patterns 15) to generate double scale roughness were required to increase the water contact angle. Thus, not only dragging coat of the composite suspension at appropriate condition but also water shower process were required for preparing highly water-repellent surfaces.…”