Faculty of Engineering
To nurture students who can play an active role in the world through their research
In this issue of “Tell Us Teacher,” we talked with Professor Takahiro Namazu, who has been conducting research on nanomaterials that will become the foundation for new technological innovations in fields ranging from semiconductor devices, which are an indispensable component of the IoT revolution, to automobiles and aircraft.
I have always enjoyed making plastic models and drawing pictures since I was a child. I was especially fond of cars, and even wanted to become a Formula 1 driver. When I went to university, I decided to study mechanical engineering in order to get involved in the automotive industry, which was my first step into this world.
Later, in April 1996, when I was a senior undergraduate student at Ritsumeikan University, I decided to enter the world of nanomaterials, which is my current field of expertise. I had hoped to enter a laboratory researching internal combustion engines for automobiles, but I was unable to do so and was assigned to a production processing laboratory. While my colleagues around me were making new grinding wheels and processing difficult-to-cut materials, some of the most advanced equipment at the time, an atomic force microscope (AFM), was brought into the laboratory, and I was assigned a topic related to nanofabrication. I remember learning the principles of the equipment from scratch for the first time and becoming completely absorbed in the many experiments I conducted.
An AFM is a microscope that uses tiny needles called cantilevers to trace the surface of a material and detect atomic-level irregularities. The tip of the needle has a small radius of about 10 nm (nanometers) and it can be used to perform various nanofabrications by applying force or electric currents to the target surface. In my experiments, I applied an electric current to the needle tip of the AFM to locally oxidize the surface of a silicon wafer, and combined it with etching to create a silicon nanobridge structure (a fixed beam structure at both ends in terms of material mechanics) with a width of about 200 nm. We also took up the challenge of measuring the strength of this structure, and found that the strength increases as the size of the material decreases, and that there is no size effect on Young’s modulus* in the nano to millimeter range. I wondered to what extent the Young’s modulus deviated from a certain value when the material was reduced in size, and whether that size was the limit at which the material could be treated as a continuum. I was fascinated by the world of nanomaterials, which is invisible to the naked eye, and was strongly attracted to the experimental identification of the boundary size between continuum and atomic aggregates.
*Young’s modulus is the proportional constant of strain and stress in the coaxial direction in the elastic range where Hooke’s law is valid.
Ｑ：After obtaining the doctoral degree, you have begun to conduct full-scale research.
Yes, that’s right. After obtaining my doctorate at Ritsumeikan University, I worked as an assistant professor at the University of Hyogo, where I developed an original experimental technique to precisely measure the mechanical properties of micro materials such as thin films. The reason why I started with micro testing technology instead of nano testing technology is because the technical difficulty of nano testing is extremely high and I felt that it would be reckless to start with nano testing technology. As a micro material testing technology, we developed a number of original testing devices, such as uniaxial and in-plane orthogonal biaxial tensile testing devices for thin films and tensile testing devices in an electron microscope. However, in the course of conducting these experiments, I lost interest in the experiments in which students used up the micro test specimens that they had fabricated in about a month using semiconductor processing technology in just one minute.
So we started by making our own sputtering equipment for making thin films. Together with the students, I drew up the plans from scratch and we started our research on metal multilayer films using our in-house three-source DC sputtering system. These films are made of light metals and transition metals deposited in layers of several nm to several tens of nm in thickness, and have the unique feature that an exothermic reaction occurs when an external micro-stimulus is applied, and the reaction propagates through the film at high speed. Using this exothermic film as an instantaneous local heat source, we have established a unique technology for bonding silicon wafers and other materials in less than one second. This research was selected as a “JST PRESTO” project, and the research on making materials was greatly accelerated as a result. During this time, we also started to develop nano-testing technology and succeeded in developing strength testing technology for nano-materials using MEMS (Micro Electro Mechanical Systems). We are now able to conduct strength tests of carbon nanotubes (CNTs) and silicon nanowires in an electron microscope.
During this period, I worked as an associate professor at the University of Hyogo and then as a professor at Aichi Institute of Technology, and in April 2020, I was appointed as a professor at the Faculty of Engineering of KUAS. In addition to research on elucidating the mechanical properties of nanomaterials such as carbon nanotubes and instantaneous bonding technology using exothermic multilayers, we have started a new research project on adding exothermic functions to nanoparticles. We are pushing ourselves to conduct highly original and challenging research, and we are working vigorously every day to achieve new goals.
Ｑ：What is your current research focus? And in what ways do you want to give back to society in the future?
I am currently focusing on the following two areas of research. I will briefly introduce each of them.
The most important thing, however, is to send students out into the world who can play a global role by developing their professional skills and mindset through their research. I believe that the best way to give back to society is to create graduates who can stand on their own feet and do useful work for the world. In my laboratory, students take the initiative in thoroughly collecting experimental data, and are encouraged to actively pursue any conclusions they can draw from it.
Ｑ：Please tell us about your hobbies, interests and things you were into during your time as a student.
There are three things that I was passionate about when I was a student. These were music, cooking, and research. As for music, I used to play the drums, so I formed a band with my good friends and worked hard on composing and practicing every day. We wrote original songs that were a mixture of jazz and pop music, and performed live. We won the second prize in an amateur band contest, and the group that won the contest went on to make a major debut.
As for cooking, I worked part-time in the kitchen of a Chinese restaurant in Yamashina, Kyoto for nine years when I was a university student. The master of the restaurant was a native of my hometown, and he was a strict boss but took me in like an apprentice through cooking. I learned how to chop vegetables, use a wok, and season food from scratch, and now I can make all kinds of Chinese food. I still go back to that restaurant to this day, and the master is like a father to me.
As for my research, as I mentioned earlier, I became interested in “seeing and manipulating small objects that are invisible to the naked eye, and learning about their characteristics”. What I have learned and am still learning through all of this is to “never lose sight of the point”, to “aim for the best and never compromise”, and to “always finish what you start”. Every day I feel that it is important to have big dreams and goals in life and to remember that every moment is precious.
Learn more about Dr. Takahiro Namazu
The Fascinating World of Atoms
Ｑ：Why did you choose the world of engineering?I have always enjoyed making plastic models and drawing pictures since I was a child. I was especially fond of cars, and even wanted to become a Formula 1 driver. When I went to university, I decided to study mechanical engineering in order to get involved in the automotive industry, which was my first step into this world.
Later, in April 1996, when I was a senior undergraduate student at Ritsumeikan University, I decided to enter the world of nanomaterials, which is my current field of expertise. I had hoped to enter a laboratory researching internal combustion engines for automobiles, but I was unable to do so and was assigned to a production processing laboratory. While my colleagues around me were making new grinding wheels and processing difficult-to-cut materials, some of the most advanced equipment at the time, an atomic force microscope (AFM), was brought into the laboratory, and I was assigned a topic related to nanofabrication. I remember learning the principles of the equipment from scratch for the first time and becoming completely absorbed in the many experiments I conducted.
An AFM is a microscope that uses tiny needles called cantilevers to trace the surface of a material and detect atomic-level irregularities. The tip of the needle has a small radius of about 10 nm (nanometers) and it can be used to perform various nanofabrications by applying force or electric currents to the target surface. In my experiments, I applied an electric current to the needle tip of the AFM to locally oxidize the surface of a silicon wafer, and combined it with etching to create a silicon nanobridge structure (a fixed beam structure at both ends in terms of material mechanics) with a width of about 200 nm. We also took up the challenge of measuring the strength of this structure, and found that the strength increases as the size of the material decreases, and that there is no size effect on Young’s modulus* in the nano to millimeter range. I wondered to what extent the Young’s modulus deviated from a certain value when the material was reduced in size, and whether that size was the limit at which the material could be treated as a continuum. I was fascinated by the world of nanomaterials, which is invisible to the naked eye, and was strongly attracted to the experimental identification of the boundary size between continuum and atomic aggregates.
*Young’s modulus is the proportional constant of strain and stress in the coaxial direction in the elastic range where Hooke’s law is valid.
Ｑ：After obtaining the doctoral degree, you have begun to conduct full-scale research.
Yes, that’s right. After obtaining my doctorate at Ritsumeikan University, I worked as an assistant professor at the University of Hyogo, where I developed an original experimental technique to precisely measure the mechanical properties of micro materials such as thin films. The reason why I started with micro testing technology instead of nano testing technology is because the technical difficulty of nano testing is extremely high and I felt that it would be reckless to start with nano testing technology. As a micro material testing technology, we developed a number of original testing devices, such as uniaxial and in-plane orthogonal biaxial tensile testing devices for thin films and tensile testing devices in an electron microscope. However, in the course of conducting these experiments, I lost interest in the experiments in which students used up the micro test specimens that they had fabricated in about a month using semiconductor processing technology in just one minute.
So we started by making our own sputtering equipment for making thin films. Together with the students, I drew up the plans from scratch and we started our research on metal multilayer films using our in-house three-source DC sputtering system. These films are made of light metals and transition metals deposited in layers of several nm to several tens of nm in thickness, and have the unique feature that an exothermic reaction occurs when an external micro-stimulus is applied, and the reaction propagates through the film at high speed. Using this exothermic film as an instantaneous local heat source, we have established a unique technology for bonding silicon wafers and other materials in less than one second. This research was selected as a “JST PRESTO” project, and the research on making materials was greatly accelerated as a result. During this time, we also started to develop nano-testing technology and succeeded in developing strength testing technology for nano-materials using MEMS (Micro Electro Mechanical Systems). We are now able to conduct strength tests of carbon nanotubes (CNTs) and silicon nanowires in an electron microscope.
During this period, I worked as an associate professor at the University of Hyogo and then as a professor at Aichi Institute of Technology, and in April 2020, I was appointed as a professor at the Faculty of Engineering of KUAS. In addition to research on elucidating the mechanical properties of nanomaterials such as carbon nanotubes and instantaneous bonding technology using exothermic multilayers, we have started a new research project on adding exothermic functions to nanoparticles. We are pushing ourselves to conduct highly original and challenging research, and we are working vigorously every day to achieve new goals.
Ｑ：What is your current research focus? And in what ways do you want to give back to society in the future?
I am currently focusing on the following two areas of research. I will briefly introduce each of them.
1.Elucidation of the mechanical properties of atomic to nanostructured materials
How does the strength of materials change when the object size is reduced to its absolute extremes? We are trying to clarify the strength of several nm sizes in an electron microscope with our original technology that makes full use of MEMS and nano processing technology. Recently, we succeeded in experimentally obtaining answers about the correlation between the strength and structure of single-walled CNTs. We demonstrated for the first time in the world that CNTs with smaller diameters and with shapes closer to an armchair possess higher strength, and some of these results were published in Nature Communications in 2019.
By implementing this research in device design, we can contribute to the development of “unbreakable” devices with excellent long-term reliability. The current challenge in CNT research is to increase the size of CNTs without decreasing their strength, and if this becomes technically possible, it will greatly contribute to the realization of large structures such as space elevators.
2.Development of self-propagating heat generating materials
When a nano-thick layer of two different metals is given a small external stimulus, it becomes an alloy and generates heat. Since the amount of heat generated can be freely engineering through the combination of metals, atomic ratios, thicknesses, etc., the material can be given a heat-generating performance tailored to whatever the process calls for. It is a completely different heat source from other heating methods such as electric heaters, which makes it possible to do things that are impossible with conventional technologies. For example, instantaneous bonding technology using Al/Ni multilayers can bond two silicon wafers together in less than 0.1 second. Since no gas is generated during the heating process, this technology is not only energy-saving but also environmentally friendly, and is expected to play an active role in the mounting of power semiconductor devices for electric vehicles and next-generation medicine.
How does the strength of materials change when the object size is reduced to its absolute extremes? We are trying to clarify the strength of several nm sizes in an electron microscope with our original technology that makes full use of MEMS and nano processing technology. Recently, we succeeded in experimentally obtaining answers about the correlation between the strength and structure of single-walled CNTs. We demonstrated for the first time in the world that CNTs with smaller diameters and with shapes closer to an armchair possess higher strength, and some of these results were published in Nature Communications in 2019.
By implementing this research in device design, we can contribute to the development of “unbreakable” devices with excellent long-term reliability. The current challenge in CNT research is to increase the size of CNTs without decreasing their strength, and if this becomes technically possible, it will greatly contribute to the realization of large structures such as space elevators.
2.Development of self-propagating heat generating materials
When a nano-thick layer of two different metals is given a small external stimulus, it becomes an alloy and generates heat. Since the amount of heat generated can be freely engineering through the combination of metals, atomic ratios, thicknesses, etc., the material can be given a heat-generating performance tailored to whatever the process calls for. It is a completely different heat source from other heating methods such as electric heaters, which makes it possible to do things that are impossible with conventional technologies. For example, instantaneous bonding technology using Al/Ni multilayers can bond two silicon wafers together in less than 0.1 second. Since no gas is generated during the heating process, this technology is not only energy-saving but also environmentally friendly, and is expected to play an active role in the mounting of power semiconductor devices for electric vehicles and next-generation medicine.
The most important thing, however, is to send students out into the world who can play a global role by developing their professional skills and mindset through their research. I believe that the best way to give back to society is to create graduates who can stand on their own feet and do useful work for the world. In my laboratory, students take the initiative in thoroughly collecting experimental data, and are encouraged to actively pursue any conclusions they can draw from it.
Ｑ：Please tell us about your hobbies, interests and things you were into during your time as a student.
There are three things that I was passionate about when I was a student. These were music, cooking, and research. As for music, I used to play the drums, so I formed a band with my good friends and worked hard on composing and practicing every day. We wrote original songs that were a mixture of jazz and pop music, and performed live. We won the second prize in an amateur band contest, and the group that won the contest went on to make a major debut.
As for cooking, I worked part-time in the kitchen of a Chinese restaurant in Yamashina, Kyoto for nine years when I was a university student. The master of the restaurant was a native of my hometown, and he was a strict boss but took me in like an apprentice through cooking. I learned how to chop vegetables, use a wok, and season food from scratch, and now I can make all kinds of Chinese food. I still go back to that restaurant to this day, and the master is like a father to me.
As for my research, as I mentioned earlier, I became interested in “seeing and manipulating small objects that are invisible to the naked eye, and learning about their characteristics”. What I have learned and am still learning through all of this is to “never lose sight of the point”, to “aim for the best and never compromise”, and to “always finish what you start”. Every day I feel that it is important to have big dreams and goals in life and to remember that every moment is precious.
Learn more about Dr. Takahiro Namazu