Nonlinear Friction Dynamics of Oil-in-Water and Water-in-Oil Emulsions on Hydrogel Surfaces
Nonlinear Friction Dynamics of Oil-in-Water and Water-in-Oil Emulsions on Hydrogel Surfaces
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DOI：
10.1021/acs.langmuir.1c01339
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发表时间：
2021-06-22
期刊：
影响因子：
3.9
通讯作者：
Nonomura, Yoshimune
中科院分区：
文献类型：
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作者：
Kikuchi, Kei;Mayama, Hiroyuki;Nonomura, Yoshimune
在这项研究中，乳液在口腔环境中的摩擦性能进行了研究，以了解生物表面上发生的食物质地识别机制。许多出版物已经表明，摩擦现象取决于摩擦条件，如表面特性，以及接触探针的形状和运动。传统的摩擦评估系统不适合模拟口腔环境。因此，在这项研究中，使用正弦运动摩擦评价系统，有效地模仿口腔环境的乳液中的两个分形琼脂凝胶基质之间的摩擦力进行了检查。分形琼脂凝胶的物理性质，包括弹性，亲水性和表面粗糙度，类似于人的舌头。此外，正弦运动模仿生物体的运动。根据样品，观察到三种摩擦曲线。对于水、表面活性剂水溶液和橄榄油，向外和向里过程的摩擦轮廓是对称的（稳定模式）。有趣的是，对于水包油（O/W）乳液，注意到不仅具有不对称摩擦曲线（不稳定模式I）而且具有润滑现象的摩擦行为，所述润滑现象暂时降低摩擦力（不稳定模式II）。随着O/W乳液含油量的增加，凝胶基质之间出现不稳定图案和粘附力的可能性增加。这些特征性摩擦现象归因于夹在琼脂凝胶基质之间的乳液中的强粘附力。本研究的结果将有助于理解生物表面上的食物质地识别机制和动态现象。
In this study, the friction properties of emulsions in an oral environment were investigated to understand the food-texture recognition mechanisms occurring on biological surfaces. Numerous publications have suggested that the friction phenomena depend on friction conditions, such as the surface characteristics, as well as the shape and movement of contact probes. Traditional friction evaluation systems are unsuitable for mimicking the oral environment. Thus, in this study, the friction forces between two fractal agar gel substrates in an emulsion were examined using a sinusoidal motion friction evaluation system that effectively mimics the oral environment. The physical properties of the fractal agar gel, including the elasticity, hydrophilicity, and surface roughness, were analogous to those of the human tongue. Furthermore, the sinusoidal motion imitated the movements of living organisms. Depending on the samples, three friction profiles were observed. For water, the surfactant aqueous solution, and olive oil, the friction profiles of the outward and homeward processes were symmetric (stable pattern). Interestingly, for an oil-in-water (O/W) emulsion, friction behaviors with not only an asymmetric friction profile (unstable pattern I) but also a lubrication phenomenon, which temporarily decreased the friction force (unstable pattern II), were noted. The probability for the appearance of unstable patterns and adhesion force between the gel substrates increased with the oil content of the O/W emulsions. These characteristic friction phenomena were attributed to the strong adhesive force in the emulsion, which was sandwiched between the agar gel substrates. The findings obtained in this study would contribute significantly to understanding the food-texture recognition mechanisms and dynamic phenomena occurring on biological surfaces.