Japan – VISMAYA – History & Philosophy of Physics

Where Ideas Merge: A Visit to the Institute of Science Tokyo

New ideas are often created by the merging of two old ideas. How often is this true, and how often do we tend to forget this?

Today I visited the Institute of Science Tokyo, formerly known as Tokyo Tech. This is a new avatar of a very interesting institution funded by the government of Japan. By merging the Tokyo Institute of Technology with the Tokyo Medical and Dental University, a very interesting concept has emerged: the Institute of Science Tokyo. These two institutions have been important pillars of the research and educational landscape of Tokyo, and I had the privilege of visiting this new place, which is a result of a new merger.

Thanks to the invitation and fantastic hospitality of Prof. Daiki Nishiguchi, a faculty member in the Physics Department of the Institute of Science Tokyo, I had a memorable experience. I met Daiki a couple of years ago at the University of Tokyo, where he previously held a faculty position. Recently, he has moved to the Institute of Science Tokyo to establish his independent research group as an Associate Professor.

Daiki has done amazing work on topological soft matter, and his recent results include remarkable observations related to turbulence and vorticity in suspensions of bacteria under spatial confinement. He has also been setting up interesting experiments involving Janus particles, and I got a nice overview of his work. Thanks to him and his research group, I got a flavor of the research being carried out in their lab, and I was also treated to a wonderful lunch by Daiki.

I gave a physics seminar on some of our work on structured light and confinement of soft matter, especially thermally active colloidal matter in optothermal potentials. Since Daiki and his group (see image below) have expertise in topological soft matter, my seminar emphasized structured topological beams, including ring optical beams and optical vortices. I gave an overview of our experimental results and highlighted the prospect of utilizing the topology of light to interact with topological soft matter.

There is much to explore at this interface, and again, it brings me back to the point that new ideas often emerge from the merging of evolving old ideas, such as topological light and topological soft matter.

This is my third visit to Japan, and I always find their calm, focused, and deeply committed research environment inspiring. There is much to learn from their approach to science and technology, and my visit to the Institute of Science Tokyo reinforced this thought.

I thank Daiki and his research group for the wonderful time I had at their laboratory and offer my best wishes to him in his new explorations.

Talk at Kyoto University

Whereas Sunday was bright, sunny, and clear for outdoor activities, Monday started cloudy with a forecast of rain. I started from my living place to Kyoto University around 10 in the morning. I took the city bus, which shuttles people from the city centre to the university. Within half an hour, I was in a serene, green, and beautiful campus, typical of a Japanese university. Kyoto University has a rich blend of modern and ancient architecture, and I was not surprised to see a large maroon-coloured ark at the entrance of the university.

With Prof. Tetsuro, who hosted me at the Graduate School of Informatics at Kyoto University.

I met Tesuji Tetsuro upon arrival (our previous in-person meeting was in the 2023 Optics & Photonics Congress on optical manipulation at Yokohama). He had just arrived from his run (he is a regular marathon runner), and we had a brief chat. He had arranged an office for me to occupy for the day. We had a short discussion and thereafter went for lunch. Prof. Kazuo Aoki (Tetsuro’s erstwhile advisor at Kyoto University) accompanied us, and I was delighted to meet him. We had a delicious lunch at a small Italian restaurant.

Around 3 pm, we met at the seminar hall where I gave my talk titled Hot Brownian Dynamics Driven by Structured Light. One of the key points I emphasized in my talk was the relevance of structured light in driving Brownian dynamics of colloids. I spoke about various parts of the stochastic differential equation (see equation 1 below) that represent the dynamics of a colloidal system interacting with an external force.

A key element of my discussion was the generalized driving force on the right-hand side of the equation, where the conventional restoring force in an optical trap can be generalized to an external driving force due to structured light. This versatile force is a result of a large set of linear and angular momentum states of structured light. These states can drive soft matter, further resulting in unconventional assembly and dynamics. Furthermore, the generalized driving force can include not only the optical force but also the thermal and hydrodynamic effects initiated by optical illumination. The combination of these forces culminates in a resultant force, offering an unconventional driving mechanism to drive the structure, assembly, and dynamics of colloids and other kinds of soft matter systems, including droplets and fluids. I showed some of our experimental results related to the above-mentioned concepts with emphasis on rotational and orbital degrees of freedom. I also presented our recent results on synchronization in an optothermal trap.

We had a long discussion on how to measure fluid dynamic properties around such colloids, especially when there is an external perturbation force, such as a laser beam, which can itself influence the colloidal dynamics. Tetsuro also mentioned his protocols and certain simulation strategies utilized to study thermo-osmotic flows in such situations. I learned about interesting methods they have been developing to numerically simulate the interactions using differential temperatures. The strategy is interesting and deserves further attention by the community. He also showed his experimental setup and gave a tour of his laboratory facilities.

Overall, it was a long, thoughtful day with wonderful discussions on topics of common scientific interest. We ended with a delicious dinner at a Japanese izakaya, and I thank Tetsuro for his invitation and hospitality. Kyoto University has a wonderful atmosphere for research, and I hope to visit again.

Kyoto digital archives 02 – Japan’s physics Who’s Who…

Continuing on archival research on physics @ Kyoto, I found a remarkable photo.

The who’s who of Japan’s theoretical physics (and future Nobels) in 1951. They were meeting at Kyoto to establish an inter-university research institute.

This photo was further reproduced at :

Takaiwa, Yoshinobu, Masako Bando, Haruyoshi Gotoh, Hisao Hayakawa, Kohji Hirata, Kazuyuki Ito, Kenji Ito, et al. 2014. “Memorial Archival Libraries of Yukawa, Tomonaga, and Sakata.” In Proceedings of the 12th Asia Pacific Physics Conference (APPC12). Vol. 1. JPS Conference Proceedings 1. Journal of the Physical Society of Japan. https://doi.org/10.7566/JPSCP.1.019005.

Kyoto digital archives 01 – Yukawa’s book

Duff’s famous physics textbook from 1900 (5th edition) owned by Yukawa

Yukawa’s name on the book

Hideki Yukawa’s picture on the Nobel website

Apart from sipping the wonderful Japanese coffee and exploring the streets of Kyoto on foot, I have been looking into the archives of Kyoto University. I am mainly searching for records and books related to their physics department, and obviously, one of the names that pops out very often is Hideki Yukawa.

Yukawa was one of the Nobel laureates from this university. He obtained his Nobel Prize in Physics in 1949 for his prediction of the existence of mesons on the basis of theoretical work on nuclear forces. He is a big name in physics, and there is a physical potential named after him, which means one can understand the intellectual heft he carries as a physicist. Yukawa spent most of his scientific career at Kyoto, specifically at the Kyoto Imperial University (now, no more imperial :-) ), and is regarded as one of the inspirations for a battery of many excellent theoretical physicists to have emerged out of not only Kyoto but also Japan, and perhaps many parts of the world.
While looking through the archival records, I came across one of the textbooks owned by Yukawa, which has his signature on it. It made my day !

The textbook titled “A Text-Book of Physics,” edited by A. Wilmer Duff, is a classic. Yukawa had the 5th edition (1921), and this book went on to have 3 more editions. I hope to write more about this particular textbook because the author, Wilmer Duff, had a connection to Madras University (as a Professor) in India and was also on the faculty of my post-doc alma mater – Purdue University !

The scientific world is a small place with unanticipated, wonderful connections :-)

Osaka and Optical Manipulation

Thanks to the invitation of Prof. Hajime Ishihara, I visited Osaka from 29th April to 2nd May 2023.

I arrived in Osaka on Saturday (29th Apr). On 30th Apr (Sunday) I headed out to visit the famous Kiyomizudera Temple in Kyoto with 2 PhD students from Ishihara’s group : Hideki Arahari and Takao Horai

Kiyomizudera Temple towards the right and beautiful landscape surrounding it.

Apart from the temple, we had a wonderful time exploring the Nishiki Market and Kamo river.

On 1st May, I visited Osaka University to officially meet Prof Ishihara, his group and other research groups in the university. We had a wonderful discussion on optical manipulation and major projects related to it especially in Japan, and undoubtedly Osaka has emerged as a major center in optical manipulation.

I was delighted to see so many students and research groups interested in optical trapping/manipulation and related science and technology. I learnt about some very interesting applications of optical manipulation. Also, it was great to see such a great sense of humor in this group of researchers. It was truly amazing.

Science + Humor …..we had a great time..

I also visited labs of Prof. Ashida and Prof Ito, and got a very nice overview of their work including optical manipulation in liquid helium and photochemical reactions in an optical trap.

At 4pm, I gave my talk on “Optical Manipulation based on Opto-Thermal Gradients“. I elaborated on the role of absorption and related thermal gradient in optical manipulation. I presented some of our ongoing work on optical manipulation with structured light. The talk was attended by at least 30 to 40 people, and I was informed that students from various groups in Osaka were present (there are a few universities). The quality of questions and the follow up discussion was very good, and really enjoyed it.

Finally, the day ended with a wonderful dinner at a tofu-themed Japanese restaurant. We had wonderful discussion on history and philosophy in our countries, and was very interesting.

Dinner with Professors Ishihara, Ito, Ashida and Yokoyama

My trajectory in Japan has been Yokohama –> Tokyo –> Okinawa –> Osaka. After 16 days, one conference talk and 4 research seminar across Japan, I am now heading back from Osaka to Tokyo (and writing this blog) on Shinkansen – the bullet train. Tomorrow, I will be leaving to India.

In Japanese, the word ‘Osaka’ also means ‘a large hill’. Japan’s geography has many large hills (see a picture of Mt. Fuji I took from the moving Shinkansen), and metaphorically speaking Japanese like to scale complex landscapes of life by bringing culture with science and technology. There is a lot to learn from this approach to life.

Osaka, optical manipulation and the perennial ascent towards knowledge. What a memorable trip this has been.

To Japan and to all the people I met here – Doumo Arigatou Gozaimasu !

Ocean, Okinawa and OIST…

I had a memorable visit to Okinawa Institute of Science and Technology – OIST (27th and 28th April 2023). Prof. Mahesh Bandi was my host, I had a fabulous time interacting with him and a few other groups. Below are some (of many) highlights.

First, the geography : located in the midst of the ocean(s), away from the mainland Japan, Okinawa is the southern most part of Japan. I took a 2.5 hrs. flight from Tokyo and reached the destination when it was dark.

In the morning, I woke up and opened the window to be pleasantly surprised to see the beautiful ocean in my field of view. Below is a photo I took from the balcony of the room.

At the outset, I had a fabulous discussion. Mahesh and I had a excellent free-wheeling discussion on various topics including science, arts and history. Also, I visited his lab to see very creative experiments on non-equilibrium physics including some fascinating experimental designs to probe dynamics at liquid-air interface. He has a fabulous set of students working on interesting problems. It was both refreshing and stimulating.

In the afternoon, I gave my seminar and below is an interesting announcement (because it spells out my full name :-)). I discussed about some non-equilibrium aspects of our work, and towards the end emphasized some interesting prospects of statistical optics in an optothermal-assembly.

After my talk, I had illuminating discussion with Prof. Pinaki Chakraborty on thermal diffusion, fluid dynamics and history of science. I enjoyed visiting his lab, in which they have built one of the biggest Taylor-Couette flow set up I have ever seen (see the frame behind Pinaki in the picture below).

Next day, I had an elaborate lab tour of Prof. Sile Nic Chormaic, who is an expert in various topics related to optics/photonics including optical trapping. As she was travelling, her post-doc Dr. Souvik Sil, hosted me and took me around to show various aspects of their lab. It was a great learning experience.

On the same day, I visited the cutting-edge lab of Prof. Keshav Dani. Since he was travelling, his team members gave me a brief tour and I was amazed by some of their experiments.

Another major highlight of my trip was to meet many IISER students. Specifically, I met Amit Bhunia (post-doc) and Saurav Raj (PhD student) who are IISER Pune alumnus. I also met many IISER Kolkata students (Souvik being one of them).

Overall, I was mighty impressed by the research infrastructure at OIST and the people working there. It is quite remarkable how they have been able to build such a great facility in such a short time (their campus started around 2010).

Today, I have reached Osaka, and on Monday will be giving a talk and visiting a few groups at Osaka Unviersity. Prof. Hajime Ishihara is my host, and I look forward to plenty of interaction on optical manipulation.

Two talks in Tokyo

Wonderful Japanese-Gothic architecture at The University of Tokyo

I gave two talks in Tokyo.

First was on 24th April at Department of Applied Physics, Faculty of Advanced Engineering, Tokyo University of Science. My host was Prof. Yutaka Sumino. I spoke about “Soft Matter in Opto-Thermal Gradients“. I gave a short introduction to opto-thermal perturbations and potentials, and discussed some of our work on opto-thermophoretic trapping and Brownian dynamics. The audience contained a few master students too, and I really enjoyed discussing some concepts related to Brownian motion in an optothermal trap, and related experiments. Also, I had a very interesting discussion with Sumino and his students on their experiments on Janus particles.

The second talk was on 25th April at Department of Physics, University of Tokyo. My host was Prof. Kazumasa Takeuchi. I spoke about “Soft Matter in Opto-Thermal Gradients : Evolutionary Dynamics and Pattern Formation“.

This talk was also announced on Japan’s statphys mailing list, and also live-casted over zoom. I discussed about the origins of optothermal effects in a laser trap, and how it can lead to some interesting dynamics and pattern formation in soft-matter system. Specifically, I highlighted the concept of Hot Brownian motion, and how it can be influenced using thermo-plasmons. The talk and discussion went on for almost 2 hours, and I really loved it. Also, Takeuchi and his students gave an overview of their work including a live demonstration on turbulence in liquid crystals, and it was fantastic.

Cup Noodles Museum – Food + Science + Technology + Inspiration

Here is the video blog on the Cup Noodles Museum at Yokohama. I visited this place recently, and was inspiring. Also, has some connections to history of science and scientists. Some notes/references at the end.

Notes & References :

CUPNOODLES MUSEUM YOKOHAMA (no date) CUPNOODLES MUSEUM YOKOHAMA. Available at: https://www.cupnoodles-museum.jp/en/yokohama/ (Accessed: 22 April 2023).

‘Hideki Yukawa’ (2023) Wikipedia. Available at: https://en.wikipedia.org/w/index.php?title=Hideki_Yukawa&oldid=1148467040 (Accessed: 22 April 2023).

‘Momofuku Ando’ (2023) Wikipedia. Available at: https://en.wikipedia.org/w/index.php?title=Momofuku_Ando&oldid=1143758937 (Accessed: 22 April 2023).

Space Noodles | Science and Education | Trends in Japan | Web Japan (no date). Available at: https://web-japan.org/trends01/article/020920sci_r.html (Accessed: 22 April 2023).

‘Cup Noodle’s Nissin develops space ramen, space curry rice for astronauts to eat among the stars’ (2020) SoraNews24 -Japan News-, 17 September. Available at: https://soranews24.com/2020/09/17/cup-noodles-nissin-develops-space-ramen-space-curry-rice-for-astronauts-to-eat-among-the-stars/ (Accessed: 22 April 2023).

The Nobel Prize in Physics 1949 (no date) NobelPrize.org. Available at: https://www.nobelprize.org/prizes/physics/1949/yukawa/biographical/ (Accessed: 22 April 2023).

OMC 2023

We had a great discussion after the talk… spoke on how temperature gradients can be harnessed for optical manipulation in colloidal fluids… which further leads to some interesting Brownian dynamics

The 10th Optical Manipulation and Structured Materials Conference (OMC2023) was superb….learnt a lot.
This was part of Optics & Photonics International Congress 2023

Thanks to Prof. Takashige Omatsu for the invitation and amazing Japanese hospitality…

Halina Rubinsztein-Dunlop – History of Optical Manipulation

Below is a video blog featuring Halina Rubinsztein-Dunlop as part of history of optical manipulation. Also pictured in the blog are : Giorgio Volpe (UC, London) and Agnese Callegari (University of Gothenburg). Pictures taken at OMC 2023 in Yokohama, Japan.

Some relevant links at the end :

Notes :

Professor Halina Rubinsztein-Dunlop (2023). Available at: https://smp.uq.edu.au/profile/204/halina-rubinsztein-dunlop (Accessed: 19 April 2023).

Halina Rubinsztein-Dunlop‬ – ‪Google Scholar‬ Available at: https://scholar.google.se/citations?user=4_sqVfYAAAAJ&hl=en (Accessed: 19 April 2023).

‘Halina Rubinsztein-Dunlop’ (2023) Wikipedia. Available at: https://en.wikipedia.org/w/index.php?title=Halina_Rubinsztein-Dunlop&oldid=1145639271 (Accessed: 19 April 2023).

seminal papers :

Friese, M.E.J. et al. (1998) ‘Optical alignment and spinning of laser-trapped microscopic particles’, Nature, 394(6691), pp. 348–350. Available at: https://doi.org/10.1038/28566.

He, H. et al. (1995) ‘Direct Observation of Transfer of Angular Momentum to Absorptive Particles from a Laser Beam with a Phase Singularity’, Physical Review Letters, 75(5), pp. 826–829. Available at: https://doi.org/10.1103/PhysRevLett.75.826.

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