Soft Matter Laboratory (KURITA LAB)

Department of Physics, Graduate School of Science
Division of Physics, Faculty of Science

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Research themes

Soft matters are a group of materials that are easily deformed by weak stresses like thermal fluctuations. Typical examples of soft matters include liquid crystals, polymers, colloids, foams, gels, granular materials, and a number of biological materials. We see many soft matters in our daily life, such as liquid crystal displays, soaps, plastics, hair spray, ground coffee beans, and so on. You may think the physics governing these materials is already well understood, but it is not. Because dynamics of soft matters are too complicated to comprehend, almost all processes of making products like those described above rely on empirical rules alone. Our goals are to understand the principles of soft matters. We believe that the achievements will improve our daily lives.
(Keyword: Soft matters, non equilibrium, phase transition)

Recent Researches

■ A discovery of a new type of solvation.

Imagine introducing a droplet of red liquid into a container of water. You may believe that the red droplet will expand, and its color will become diluted, and you would be correct, if the droplet is not an ionic liquid. Ionic liquids are composed of cation and anion and have very low melting temperatures. Recently, we discovered a new type of mixing process in an ionic liquid and water system. Dispersion of ionic liquids does not obey the usual diffusion equation. A droplet of ionic liquid has a sharp interface in water despite the miscibility of the droplet to water. This observation can not be explained by conventional theories.

■ Modeling of aggregation in biosystems.

It is known that some kind of cells aggregate as a survival strategy when they are starved. You can see beautiful network patterns in their aggregation process. We proposed a very simple model for the aggregation dynamics and successfully reproduced the network patterns in numerical simulations. Because this model is constructed with a minimal number of factors, it is expected that the model can be applied to other systems that exhibit radial network patterns.

■ Temperature gradient experiments for soft matters.

Soft matters are so sensitive to external stresses that even very weak stress like thermal fluctuations can deform them. Temperature gradients, therefore, strongly affect the dynamics of soft matters. We investigate the effect of temperature gradient on soft matter systems such as Rayleigh-Benard convections of gels and membrane systems of surfactants. Investigation of the effects of temperature gradients is important not only for basic research, but also for applications, as the temperature distribution is always heterogeneous in natural environments and practical situations.