[No. 211] Yuki Takayama

Thank you for this opportunity to contribute to the Keio University alumni column. I am currently engaged in the development of lensless nano-imaging technology, which combines X-rays generated at a huge facility called a synchrotron radiation facility with information science, and in applied research in the fields of life sciences, food and agricultural sciences, and soft materials. The reason I entered this field was that I was strongly fascinated by understanding life phenomena at the level of macromolecular structures in a biophysics class taught by Professor Masayoshi Nakasako, who was my supervisor from my undergraduate years through my Ph.D. program.

I remember deciding to major in physics when I was promoted to my second year of high school. Since childhood, my parents had taken me to science museums and on insect-collecting trips, so I had a vague interest in the natural sciences. In high school, I studied physics, chemistry, and biology in my first year, and from the second year, we were divided into a physics/chemistry track and a biology/chemistry track. The teachers were very enthusiastic, and I keenly felt the appeal of the subjects themselves. I was particularly interested in both physics and biology, so I had trouble choosing. Ultimately, I decided to pursue physics, thinking that it would allow me to understand a wide range of subjects, not just biology, in universal terms.

At the Keio University Faculty of Science and Technology, only students from Gakumon 1 could advance to the Department of Physics, so I enrolled in Gakumon 1 without hesitation and moved on to the Department of Physics in the departmental allocation in my second year. The Department of Physics was relatively small, with about 40 students per year, which I think was a good thing because it allowed us to build close relationships with everyone in our grade. During our free time between classes, we would discuss lectures, experiments, and programming assignments in the library, recommend good textbooks to each other, and go to karaoke in the "Hiyoura" area. Thanks to these interactions with my friends, I was able to enjoy a friendly and harmonious student life while maintaining high aspirations.

Although I had chosen to major in physics, I still had no specific goals in my first and second years. Therefore, as mentioned earlier, I broadened my horizons by taking a wide range of courses, including life sciences (my other interest), mechanical and electronic engineering lectures (which I thought would be necessary if I went into experimental work), and science writing (which I was not good at). Although I haven't truly mastered everything, having even a partial understanding of these subjects has been beneficial to my current work. I believe that studying at the interdisciplinary Keio University Faculty of Science and Technology was a great advantage for me.

On the other hand, I struggled to find an intersection between physics and life sciences that I could be truly passionate about, and I was still undecided about my future path. It was during this time, in the fall semester of my third year, that I took Professor Nakasako's biophysics course. Proteins, which are biological macromolecules, spontaneously form three-dimensional structures as "nanomachines" in the presence of water and express their functions through dynamic structural changes. This process is visualized using X-rays with a wavelength on the 0.1 nm scale and understood in the language of physics. "This is it!" I thought, as it strongly resonated with my interests. I remember going to talk to Professor Nakasako after the first or second lecture to tell him I wanted to pursue biophysics. Biophysics is a broad field, so I was truly lucky that there was a professor whose research perfectly matched my interests.

I was a member of the Biophysics Laboratory for a total of six years: from my fourth year as an undergraduate, through two years of the master's program, and three years of the Ph.D. program. There were two to four students in each grade, and they were such a memorable and unique group of people. We spent our days in the lab not only conducting research but also having lively discussions about our hobbies. This friendly and harmonious atmosphere might be a characteristic of the department's culture.

In the lab, until my master's program, I was engaged in developing experimental techniques for X-ray crystallography to induce and visualize protein structural changes. From the latter half of my master's program, I began to apply these techniques to develop a lensless X-ray imaging technology for observing the hierarchical structure of whole cells in three dimensions at the nanoscale. This research remains the main topic of my work, even after 14 years. It was a new technique called coherent X-ray diffraction imaging, which reconstructs a microscope image using a computational algorithm by measuring the X-ray interference pattern from the observed sample, instead of forming an image with a lens. To observe a clear X-ray interference pattern that can be analyzed, extremely powerful and coherent X-rays are required. Experiments are conducted at a huge facility that uses an electron accelerator called a synchrotron radiation facility to generate these X-rays. I conducted experiments about three times a year, staying for about a week each time, at SPring-8, a synchrotron radiation facility in Nishi-Harima, Hyogo Prefecture, that looks like a giant spaceship with a circumference of about 1.5 km. Developing new measurement techniques by bringing in equipment developed in our lab was very challenging, and sometimes we had to solve problems by sacrificing sleep during the limited beamtime. Although it was tough, I believe it helped me develop mental resilience against difficulties and problem-solving skills, which have been a great asset. Furthermore, being able to develop new measurement and analysis techniques to see what was previously unseen gave me great confidence in becoming a researcher.

After obtaining my Ph.D., I continued to advance the technology and conduct applied research while acquiring skills in electron microscopy (at RIKEN) and X-ray optics (at the University of Hyogo). During this time, my desire to apply the technologies I had developed not only to my own research but also broadly to academic research and industry grew stronger. While at the University of Hyogo, I also worked on the social implementation of these technologies as a staff member of the Hyogo Prefecture-dedicated beamline at SPring-8. Interacting with people from various fields was extremely stimulating, as it broadened my perspective and helped me discover new research seeds. Leveraging this experience, I am currently developing measurement technologies and pioneering applied research in the fields of life sciences, food and agricultural sciences, and soft materials for the use of NanoTerasu, a new synchrotron radiation facility under construction on the Aobayama New Campus of Tohoku University. I am excitedly pursuing research and development, wondering what kind of nano-world we will be able to understand by illuminating it with X-rays from NanoTerasu.