Wettability of fractal surfaces has been studied both theoretically and experimentally. The contact angle of a liquid droplet placed on a fractal surface is expressed as a function of the fractal dimension, the range of fractal behavior, and the contacting ratio of the surface. The result shows that fractal surfaces can be super water repellent (superwettable) when the surfaces are composed of hydrophobic (hydrophilic) materials. We also demonstrate a super-water-repellent fractal surface made of alkylketene dimer; a water droplet on this surface has a contact angle as large as 174°.

Super water-repellent surfaces showing a contact angle of 174° for water droplets have been made of alkylketene dimer (AKD). Water droplets roll around without attachment on the super water-repellent surfaces when tilted slightly. The AKD is a kind of wax and forms spontaneously a fractal structure in its surfaces by solidification from the melt. The fractal surfaces of AKD repel a water droplet completely and show a contact angle larger than 170° without any fluorination treatments. Theoretical prediction of the wettability of the fractal surfaces has been given in the previous paper. The relationship between the contact angle of the flat surface θ and that of the fractal surface θf is expressed by the equation cos θf = (L/l) D -2 cos θ where (L/l) D -2 is the surface area magnification factor. The fractal dimension of the solid AKD surface was determined to be D ≈ 2.3 applying the box-counting method to the SEM images of the AKD cross section. L and l, which are the largest and the smallest size limits of the fractal behavior of the surface, are also estimated from the box-counting method. The contact angles of some water/1,4-dioxane mixtures on the fractal and the flat AKD surfaces were determined, and the values of cos θf were plotted against cos θ. The plot of cos θf against cos θ agrees well with the theoretical prediction. It has been demonstrated by this work that the fractal concept is a powerful tool to develop some novel functional materials.

Surfaces that repel both water and liquid oils completely are very useful in daily life and in industry. Although surfaces with outstanding water-repellent properties have been developed and intensively studied recently," -31 surfaces with excellent oil-repellent properties, however, have not yet been reported in spite of their crucial importance. Wettability of a solid surface with a liquid is enhanced by the surface in particular by the presence of fractal structures. When the contact angle between a liquid and a flat solid surface is larger than 90", the surface repels the liquid completely if the surface rough enough.For a fractal rough structure the relationship between the contact angle of the flat surface Q and that of the rough surface 0, is expressed by the Equation (a).[2.3. In Equation (a),( L / I ) D -2 is the surface area magnification factor, L and I are the upper and lower limits of the fractal behavior of the surface, and D the fractal dimension. This idea has been realized recently for super water-repellent surfaces having the contact angle of 174", on using fractal We have applied the same concept in this work to the completely novel, super oil-repellent surfaces. The greatest difficulty in obtaining the super oil-repellent surface is to make a flat surface that has a contact angle greater than 9 0 for oils. Here the surface tension of the solid needed to achieve this condition is estimated. The contact angle 0 on the flat surface is determined by Young's equation [Eq. (b),where y s , yl,, and ysL are the surface tensions of the solid, the liquid, and the solid/liquid interfacial tension, respectively]. When the contact angle is 90", ys must be equal to ysL. The interfacial tension ysL can be approximated by Equation (c) (c) when the interaction force between the two materials is same kind. [61 Combining Equations (b) and (c), we obtain ys = yL/4 as condition for 0 = 90".Typical surface tensions of oils are 20-30 m N m -', and the value of y s must be on the order of several mNm-'. Such a small surface tension for a solid can probably be provided only by the trifluoromethyl group.['] Accordingly, our strategy for making super oil-repellent surfaces was to obtain a surface of enough roughness and then to cover the rough surface with trifluoromethyl groups by treating it with fluorinated compounds. Figure 1 shows a scanning electron microscopic photograph of the anodically oxidized rough surface of aluminum plate. This surface was analyzed by the box counting method1233J and found to be a fractal (dimension 2.16). This untreated surface is superwettable towards liquids, but can be converted into a super r-;'sr = ;'s + 71, -2b ;'s 7,.

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SynopsisThe aim of this study was to investigate the effect of iron oxide application on improving the volume of eyelashes. Iron oxide, having a negative surface charge in its natural form, was coated with commercial cationic polymers to increase its adhesion. The iron oxides coated with different types and concentrations of these polymers were incorporated into a basic mascara formula to test their volume effects by means of the weight difference of eyelashes. The results indicated that the type and concentration of coating materials affect the surface zeta potential and particle cluster size of iron oxides. The type of cationic polymer, especially, was shown to modify both factors of iron oxide. The obtained results also suggested that the volume effect of mascara increases with a higher positive surface zeta potential and a smaller particle cluster size of the coated iron oxides.J. Cosmet. Sci., 60, 627-636 (November/December 2009) Study and description of hydrogels and organogels as vehicles for cosmetic active ingredients Synopsis Cellulite, a clinical syndrome mainly affecting women, involves specific changes in conjunctive dermic and subcutaneous tissue, leading to vascular and hypertrophic alterations in adipose tissues and the consequent alteration of tissue structure. This paper describes the design of hydrogels and pluronic-lecithin organogels elaborated as vehicles of Aloe vera (Aloe vera linné) and Hydrocotyle asiatica (Centella asiatica) for the treatment of cellulite.The objective of this work was to carry out a complete evaluation of the proposed formulae through the study of the organoleptic and rheological properties of the formulae. Our work revealed that, in appearance, hydrogels show better organoleptic characteristics than organogels. On the other hand, from a rheological point of view, both hydrogels and organogels display a plastic behavior. However, the main difference between the two is that the more complex internal structure of the organogel bestows it with more viscosity. Finally, in vitro tests with Franz-type diffusion cells revealed that the release of cosmetic active principle from the tested excipients was appropriate, both in terms of magnitude and velocity.J. Cosmet. Sci., 60, 637-648 (November/December 2009) Changes in structure and geometric properties of human hair by aging SynopsisTo clarify hair changes by aging, the effect of age on hair properties was investigated from macro-to microscopic viewpoints. Sensory hair luster tests were performed on 230 Japanese females from 10 to 70 year of age, revealing that hair luster decreases with age. The age dependence of the hair diameter and the ellipticity of the hair cross section could not explain luster reduction by aging. It has been determined that an irregular increase in fiber curvature occurs with age and is a cause of luster reduction with aging. A detailed structural analysis by synchrotron radiation microbeam X-ray diffraction revealed that the inhomogeneity in the lateral distribution of the hair microstructure increas...