Challenging Possibilities of Material Research by Learning from Nature

Developing Materials Alternative to Autogenous Bone through Material Engineering Approach

HIRANO I have always wanted to talk with material science researchers and I looked forward to talking with two of you about your research. First, Professor Nakano, would you tell me about your research?

NAKANO Simply put, my current research theme is developing bone substitute materials based on bone microarchitecture. I have advanced this through my metallic material research. Major metallic materials supporting the infrastructure are iron and aluminum. Generally, these materials have cubic structures and high isotropy, or identical properties in all directions. On the other hand, structures in nature such as bone tissue have a strong anisotropy, the property of being directionally independent. For this reason, I don't think that we always need to use materials with a high isotropy in vivo. In order to make substitute materials exert their biological function, we need to use anisotropy in nature. That's why I'd like to examine the science of anisotropic materials thoroughly.

While researching aerospace materials, which was my starting line, I found that a hexagonal column structure with a high anisotropy, even if it accounted for only 10% of the whole structure, determined the properties of the material, which drew me to material science.

HIRANO So you 're saying is that if 10% of a material structure has changed, the material’s properties as a whole will change. Is that correct?

NAKANO That’s right. Since isotropy changes materials, it has been used without extra consideration. But anisotropy can be used in a desired direction when needed. It is also possible to make it exert a high function to a certain direction or even have new functions. In the beginning, I had immersed myself in metallic material research, but I gradually became interested in the possibilities of anisotropic materials. So my research interests shifted to bones, which also have anisotropy.

Knowing How to Obtain Desired Bone Strength

HIRANO What did spark your interest in bones?

NAKANO Before I started researching bones, I had been involved in isotropic material research. I examined materials of turbine blades with heat-resistance such as the titanium-aluminum alloy used in JAL Boeing 787, and found anisotropy was very important. As a material similarly supporting strength, I was attracted by the study of bones themselves and the artificial joints which alternate bony functions.

HIRANO From aircraft materials to bones? What a great leap!

NAKANO Actually, many metallic materials are used for bone treatment. I wondered if I could contribute to bioscience from the perspective of material engineering. 90 percent of bone is composed of collagen, or fibrous protein, and apatite ceramics for increasing strength. Previously, it was believed that bone strength was determined by apatite density, or bone density. However, when looking at bones at an atomic level, which material engineering is good at, it was found that the apatite orientation, or bone quality, dominates bone regeneration. This means the alignment of apatite is very important.

HIRANO Tell me about it in more detail.

NAKANO I learned that the apatite has a hexagonal column-style anisotropycrystal structure, which is also used for part of aircraft materials. Bone has a structure in which hexagonal apatite and fibrous collagen are placed regularly in one direction, providing mechanical strength to load. Additionally, I found that apatite has an excellent structure, i.e., the orientation of apatite in bone flexibly changes by load. I think that, in bones with a certain structure, the orientation changes flexibly due to cells which sense load. Uncommon among other graduate schools of engineering, our laboratory has animal feeding facilities as well. We’re trying to elucidate the principle of the formation of preferential alignment in bone microstructure in vivo.

HIRANO I think that such research is a part of bioscience research. How do you connect it with material engineering?

NAKANO Perhaps I should say I tried to learn from bones. I thought of reproducing the mechanism of bone’s microstructure at an atomic level and realizing it by substitute materials which emulate bony mechanisms. For example, by learning about artificial joints from bone microstructure, I want to produce artificial materials which function like biological bones, fit naturally into bones, and will be good through the years.

Photocatalysts Converting Sunlight into Chemical Energy

HIRANO Professor Mori, you're also a material researcher, aren't you? Please tell me about your research.

MORI I have been involved in design and development of catalyst materials since I was a student. Catalysts do not hit the limelight, but behind every chemical reaction stands a catalyst. As they say “Where there are chemical reactions, there are also catalysts,” making catalysts important as backseat players. Actually, catalyst technology is used in all facets of the environment, resource energy, chemical product manufacturing, medicines, fertilizers, and more. My research theme is the development of new artificial photonic synthesis-type photocatalysts to be driven by solar energy and produce hydrogen energy from water. The supply of solar energy to the earth's surface is 3.0×10 ²⁴ joules per year, while the humankind energy consumption is 5.5×10 ²⁰ joules per year. That is, when calculated, making a good use of just 0.02 percent of the solar energy shining down on the earth can cover all the energy that humankind needs. It may be challenging, but if we can develop it to the level of practical use, we will see some great research results with ripple effects, which will be able to solve global-scale energy problems facing humankind.

HIRANO What is a photocatalyst?

MORI It’s a material for converting solar energy, which unlimitedly shines down on the earth, into useful chemical energy. Researchers all over the world are involved in the development of photocatalysts, but their approaches are either from organic materials or inorganic materials. With the aim of making a breakthrough in this field, I’m making efforts to develop photocatalysts with features of organic materials based on metal complexes and features of inorganic materials based on porous silica.

Developing Catalysts with Higher Activity than Platinum

HIRANO Catalysts are used for processing car exhaust as well, aren’t they?

MORI Gasoline engines prevail in Japan. So, by using three-way catalysts, hydrocarbon, carbon monoxide, and nitroxide in exhaust gas are converted into harmless carbon dioxide and water, and  then exhausted. However, the platinum, rhodium, and palladium used in the process are rare and expensive precious metals so it is said that it will become difficult to secure them on a global scale. So, precious metal-independent production is being discussed.

Additionally, developing catalysts for processing exhaust gas of diesel engines, which prevail in Europe, is also an important research challenge. Diesel features a higher conversion efficiency, lower cost, and better mileage than gasoline, but it also has disadvantages such as producing nitrogen oxides and particulates such as those from China, which is a problem for Japan. Currently expensive platinum is used as a catalyst for processing diesel engine exhaust gas. So I’m proceeding with my research based on element-oriented strategies using common metals such as Fe, Cu, and Ni as alternatives. This is important research especially for resource-poor nations such as Japan.

HIRANO Are catalysts for processing diesel exhaust gas commercialized?

MORI By using a little ingenuity to copper catalysts, which are cheaper than platinum catalysts and are in abundant supply, I succeeded in developing catalysts with higher activity than platinum. However,  to put copper into practical use, it is necessary to continuously process exhaust gas whose composition and temperature momentarily change. Furthermore, security and reliability for catalysts ensuring operation not requiring maintenance for several decades is also a necessity. I’m working toward practical use of catalysts while addressing these challenges.

The “Whys” Made them Researchers

HIRANO What drove you start current research?

NAKANO I’m an Okayama native. Major iron and steel material companies such as Kawasaki Steel Corporation (currently JFE Steel Corporation) were in my backyard. At that time, new materials such as superconducting materials and shape-memory-alloys were being talked about, so I felt that material research was a limitless world of dreams. While I was studying at Osaka University, I knew that materials were a source of breakthrough in various fields. Furthermore, I saw large objects like airplanes fly over the Osaka International Airport and land on runways. I saw them at a close range; they looked as if I could scoop them up with a net. That attracted me to the world of aerospace material.

On top of that, I had an image that a material’s strength decreased as a temperature went up. But in one class, I learned that the strength of some materials increased as a temperature went up and I wondered why, Which attracted me to the world of material research.

HIRANO So the question “why” provided a spark for your research, didn’t it?

NAKANO I strongly felt that there was still something that could be explained to some extent but its whole principle was not yet clarified. Furthermore, one of the materials that I was examining had beautiful tissues, which were aligned in the form of multiple layers. I have long believed that beautiful things have some meaningful and wonderful functions. Metallic tissues also have regularity. I learned that defective structures in such a regularity could cause various incredible phenomena, which immersed me in research.

Interested in Making Things as a Child

MORI I have liked making things since my childhood. I did home carpentry and was absorbed in radio control and making plastic models. From that time, I had a vague dream of getting a job related to manufacturing. At university, I was assigned to a laboratory, encountered catalyst research, and started to think that catalysts while unspectacular things, supported our lives. I began to think that they were a profound and attractive research theme.

At that time I was involved in research, a project to use biological apatite as a catalyst material, about which Professor Nakano said earlier. Although apatite had not been fully examined as a catalyst material, I thought that, by taking advantage of its ion-exchange capacity and ion sorbability, apatite could also be used as a catalyst material. As there was no existing data, I had no other choice but to search for a way, and I started to gain results a year later. A very excellent catalyst was completed and had the best record at that time. Not only that, eventually, it was sold on the open market by a pharmaceutical company. This achievement excited me as a student and I thought I'd like to make a career in research. That was my starting line.

HIRANO I presume photocatalysts are a very competitive field of study. What is the most difficult thing?

MORI For example, the production of hydrogen energy through water decomposition using photocatalysts is called a dream reaction and is such high-level research that it is deemed lucky if it is achieved in 30 to 50 years. The principle of the production of hydrogen is already clarified and hydrogen is generated, but it needs to enhance the efficiency of photocatalysts in order to produce enough hydrogen. While the efficiency of plants’ photosynthesis is nearly 100 percent, that of an artificially-produced photocatalyst bottoms out at a low level with a small percentage. Furthermore, providing visible-light responsiveness is also one of our important challenges. There are many factors to improve activity. Researchers in the world are looking for a good combination of such factors through trial and error.

HIRANO Are you also trying to artificially build a natural photosynthesis?

MORI Some researchers try to make catalysts similar to enzyme through a biological approach, or an approach mimicking nature, but this has poor durability. From the perspective of practical use, I think an approach using inorganic material is more effective.

Limitless Possibilities of Blending

NAKANO I think, in the world of materials, the border between artificial things and natural compositions is disappearing. I really feel that merging various possibilities from both sides will create new technology and scholarship. Especially in the world of materials, there are more than 100 elements and some 80 metallic elements and the blending of these elements produces limitless possibilities. However, depending on empirical rules alone has a limit, therefore, looking for materials based on principles is essential.

HIRANO Artificial joints that you achieved through an approach based on bone properties successfully elicited metallic properties that suited a real bone mechanism, didn’t they? It must be difficult to bring artificial bone mechanisms close to a natural mechanism. What are the odds?

NAKANO I think there were few researchers in bioscience who paid attention to bone’s anisotropy. However, allotropic modification, i.e., atoms change their structures depending on forces that affect their structures, is frequently heard in material studies. It’s possible to apply and reflect what takes place in vivo into material research from another perspective.

HIRANO Even though the shape of bones do not change in vivo, their orientation is changing every second by location, isn’t it? It would be nice to have materials whose atomic order can be changed flexibly. What is the allure of research for you, Professor Mori?

MORI Catalyst activity drastically changes through countless combinations of elements, which attracts me. I’m still in a trial and error phase, but recent development of analysis technology has enabled us to observe what we could not see at an atomic level through electronic microscopes and the synchrotron radiation facility SPring-8. Furthermore, what local structures increase catalyst activity is being clarified and it has become possible to design catalysts based on theories. Additionally, in the development of hybrid catalysts consisting of advantages of organic materials and inorganic materials, rather than a simple combination of advantages, we can get unexpected functions through combination, which is an allure and a thrill of research.

“Slow and Steady” “Become a .300 Batter”

HIRANO We have many mistakes and difficulties in research. What is your research philosophy?

NAKANO I always tell my students and team staff that "You don't have an option between ‘You cannot see the wood for the trees’ and ‘You cannot see the trees for the wood.' You must see both the wood and trees." We need to dig into something from multiple perspectives while looking at the whole picture. My personal motto is 'slow and steady' stated by KAIKO Takeshi, an Akutagawa Award winner. I frequently let my emotions control me and feel myself compelled to run rather than spending a great deal of time doing something. So I always tell myself that I need to be engaged in research and education while having peace of mind and thinking through things without losing sight of the essence of things.

HIRANO I know what you mean. The time that we serve as a researcher is not longer than 30 or 40 years. Our interests are expanding endlessly, but what can we do in such a limited time? We don’t need to conclude, but we do need to hurry. It’s important not to rush without thinking but to devote ourselves into research. As the proverb goes, '“Youthful years pass quickly before one accomplishes much learning' and 'There isn't a moment to be wasted.' The important thing is we should control our pace. Differentiating a time for running from a time for walking is important, isn’t it?

MORI My teacher said to me to become a '.300 batter,' so to speak. I think he wanted to say that I would make many failures in experiments, but by learning from such failures, I should become a researcher who can publish important experimental data on three out of every ten occasions. I’m addressing research while considering the balance of quality and speed.

HIRANO Lastly, tell me about your dreams.

MORI Currently, I’m engaged in new material design based on an element strategic approach . There are many conflicts over races and religions in the world. One of them is conflicts over resources. Scientists cannot be involved in the solution of conflicts caused by races and religions, but as for material issues, we can contribute to peace building through providing new materials. I hope my research on catalysts and photocatalysts will lead to solutions to global-scale problems.

NAKANO I want to know the mechanism of preferential orientation in living things and apply it to the fields of material science and bioscience. I’d like to shift a focus from isotropy to anisotropy and establish my learning by focusing on anisotropy. I’m not a medical doctor, but as medical care in the future, in addition to medical care through bone density, if I can make a contribution to shift to orientation-oriented medical care, if only a little, I’m happy.

HIRANO Today, I enjoyed talking with these two material researchers by using ‘change’ and ‘replacement’ as keywords. Thank you both very much.

Fly High in the Future through Material Research with Dreams and Possibilities ─Comments from President HIRANO after the Talk

Osaka University’s roots reach back to Tekijuku, a private “place of learning” founded in 1838. 2013 marks the 175th anniversary of the founding of Tekijuku. The keywords of this “A Conversation Between the President and Young Researchers” in Tomorrow’s Pioneers were ‘change’ and ‘replacement.” Osaka University is going to change toward the future. I want to make every effort to achieve our great dream to make Osaka University one of the top ten research universities in the world by its 100th anniversary in 2031.

The research they talked to me about today was also filled with dreams and possibilities in the future. I was sure that efforts by such professors would open the future of Osaka University. I want them to make their dreams come true. I’ll do my best to realize my dream of making the university one of top 10 universities in the world.

NAKANO Takayoshi
A 1990 graduate of the Department of Metallic Material Engineering, School of Engineering, Osaka University, Prof. Nakano completed the Department of Metallic Material Engineering, Graduate School of Engineering, Osaka University in 1992.

He became an assistant at the Department of Material Property Engineering, School of Engineering in 1992. At the Graduate School of Engineering, he became a lecturer in 1999 and an assistant professor in 2001. He became an assistant professor at the Department of Material Production Science of the same graduate school in 2005. He became an associate professor at the Department of Material Production Science in 2007 and he has served as a professor since 2008. He also serves as a professor at the Education and Research Center for Advanced Structural and Functional Materials Design, Graduate School of Engineering and the Global Center for Medical Engineering and Informatics. Focusing on anisotropic material science, he has been involved in research regarding a crystallographic evaluation method of biological hard tissues, regenerative hard tissues, diseased hard tissues, and research regarding the clarification of apatite orientation mechanism, as well as the development of biocompatible materials and bone matrix control.

MORI Kohsuke
A 1999 graduate of the Course of chemical Engineering, Graduate School of Engineering Science, Osaka University, Prof. Mori completed the Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University in 2000. In 2003, he completed the Department of Materials Engineering Science, Graduate School of Engineering, Osaka University.

He became a post-doctoral researcher at University of California, Berkeley in 2004. At the Graduate School of Engineering, Osaka University, he became a specially appointed assistant at the Department of Materials Engineering Science in 2005, an assistant at the Division of Materials and Manufacturing Science in 2005, an assistant professor at the same division in 2007. In 2009, he became a lecturer at the same division. Since 2011, he has served as an associate professor at the same division. He has been involved in the development of optical functional materials driven by sunlight, application into energy conversion, design of metal nanocluster catalysts, its application to green chemistry, as well as the creation of environmentally-friendly catalysts with multiple functions.

HIRANO Toshio
A graduate of Osaka University's Faculty of Medicine in 1972, President HIRANO studied at NIH (U.S.) from 1973 through 1976. He became an assistant professor at Kumamoto University in 1980. He then became an assistant professor in 1984 and a professor in 1989 at Osaka University. Following that, he became the director of the Graduate School of Frontier Biosciences in 2004, and a director of the Graduate School of Medicine and the dean of the Faculty of Medicine in 2008. He assumed the the 17th presidency of Osaka University in August 2011. He served as Chairman for the Japan Society for Immunology from 2005 to 2006. He is also a member of the Council for Science, Technology and Innovation and The Science Council of Japan. He has a doctoral degree of medicine. His awards include the Sandoz Prize for Immunology, Osaka Science Prize, Academic Award of the Mochida Memorial Foundation, Medical Award, Fujiwara Prize, Crafoord Prize, Japan Prize, and Medal with Purple Ribbon by the Emperor of Japan.