The 19th century was an era of metal-based hard materials typified by iron and steel, as represented by the first industrial revolution. Then in the 20th century, a concept on new materials called polymers was proposed by Staudinger, and discussions on their nature started. In the last half of the 20th century, polymers replaced conventional “hard” materials in the form of plastics in various fields of application. Moreover, materials that take advantage of the functionalities of soft materials themselves represented by these polymers are being developed in various fields, in the forms such as LCD devices, gel, organic electronic devices, and biomaterials.

In such a way, the role played by “soft materials” which use polymers is becoming more important in our daily lives. Also, in recent days, soft materials are attracting attention as materials which have a low impact on the environment in the recycling society that encompasses from producing through usage/recycling.

On the other hand, silicon-based semiconductors which are inorganic materials also appeared in the last half of the 20th century, and they became a foundation of the second industrial revolution (information technology). In contrast with hard materials such as metal or inorganic materials, in which their structures and physical properties are understood systematically through various analytical approaches and theories, in case of soft materials, systematic researches and understanding of their structures/physical properties is difficult, and full-fledged researches have just started at last. The reason for the delay in research is due to the delay in understanding their complex hierarchical structures and dynamic properties. The characteristics of soft materials are due to the complex hierarchical structures formed by mutual interactions among various kinds of molecules, and the dynamic characteristics corresponding to these hierarchical structures show up as distinctive functions.

Now, the properties and functions of materials depend on the contents of the materials, and even more than that, they are strongly influenced by the conditions and properties of the surfaces and interfaces. The surfaces and interfaces formed by soft materials (“soft interface”) exist everywhere around us, and their major features are that they are formed by organic polymers, have a finite thickness, and have unique dynamic properties. Also, the soft interfaces themselves also assume various functions. From the research thus far, it has been presumed that major functional characteristics such as the wetting, friction/wear, adhesion, electrical properties, optical properties and biocompatibility of the soft materials themselves are largely influenced by the structure and physical properties of the soft interfaces.

Therefore, in order to get the best from the characteristics of the soft interfaces, it is critical to manipulate their structures and physical properties at will. However, the background science required to enable this manipulation has not been fully understood, and there is a strong need for systematic researches on the precise control of soft interface structures and structures/physical properties.

Soft interfaces found in nature show various distinctive behaviors and superior dynamic responsiveness compared to soft interfaces of artificial materials. Examples of high-functionality soft interfaces in nature are as follows: (1) antithrombogenic vascular surface phospholipid membrane; (2) lubricating surface of the hip joints; (3) lotus leaf surface that shows superhydrophobicity and self-cleaning property (4) desert beetle surface skin which can collect water by surface energy gradient; (5) stimulus responsive surface of flytraps; (6) adhesiveness of blue sea mussel (adhesive which stick in the water); (7) beautiful thin film of natural lacquer made from lacquer sap. These surfaces and interfaces show unique characteristics, but perfect recreation with synthetic materials have not been possible. Even their scientific understanding is inadequate.

Under such background, a research project (“ERATO”, Exploratory Research for Advanced Technology by the Japan Science and Technology Agency) which I am in charge as a research director, started last year. This project aims to understand the characteristics of soft interfaces from three directions. The team with Motoyasu Kobayashi as its group leader is doing a research regarding molecular design to fabricate new soft interfaces, rather than simply imitating nature.

The second team (group leader: Hiromi Watanabe) will attempt to clarify the role of hierarchical structures in distinctive soft interfaces in natural systems, and to establish hierarchical structural control methods which fabricate high-performance soft interfaces. The third team will analyzes the mechanism of molecular movement and friction/adhesion on the surface using scattering/spectroscopic methods, and at the same time, develop a method to characterize the dynamic movements occurring on the soft material interfaces at the molecular level by using radiation from “SPring-8”, a large synchrotron radiation facility, and neutrons from “J-PARC”, Japan Proton Accelerator Research Complex, and will aim at characterizing the phenomena and mechanism that are happening at the soft interfaces.

The basic research on soft interfaces is still in an early stage. The purpose of this project is to form a scientific foundation to clarify the nature of soft interfaces, which are soft material surfaces and interfaces, and are important from the academic and engineering aspects. Also, by building prototype equipments that utilize J-PARC or SPring-8 which are the world’s most advanced large experimental facilities, or other unique equipments, we expect that the relationship between the structures and physical properties of new soft interfaces will be clarified, and researches on this field will develop rapidly.

Moreover, from the engineering point of view, we expect that after 10 to 15 years from now, these research results can be applied to new technologies which will achieve a safe/secure society with low impact on the environment, such as: “environmentally friendly water lubrication system without using organic solvent system”; “creation of surface that prevents adhesion of dirt or microbes under various environments”; “nano-coating technology which can provide the desired friction characteristics; “coronary angioplasty (stent treatment technique) which used a self-lubricating guide wire”; “development of adhesives derived from natural products which can be used in water”; “introducing the latest nanotechnology method to traditional craft such as Japanese lacquering.”

As I mentioned above, a new academic field of “materials science of soft interface” has been established through interdisciplinary research, and I am sure that this will contribute to applications in various fields such as medical materials, electronic materials, automobile materials, micro/nanomachines, surface materials science, traditional craft, etc.

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