59. Who is a physicist?

“The physicist is most cogently identified, not by the subject studied, but by the way in which a subject is studied and by the nature of the information being sought.”

Above is an interesting quote by Sol Gruner, James Langer, Phil Nelson, and Viola Vogel from a 1995 article in Physics Today titled WHAT FUTURE WILL WE CHOOSE FOR PHYSICS?

Although written more than 25 years ago from the viewpoint of US physics community, many of the issues discussed in this article are pertinent even today. Probably more so in the Indian context.

Nice read :

What Future Will We Choose for Physics?
Sol M. Gruner, James S. Langer, Phil Nelson, and Viola Vogel
Citation: Physics Today 48, 12, 25 (1995); doi: 10.1063/1.881477
View online: https://doi.org/10.1063/1.881477

58. Optothermal Pulling of colloids using Nanowire Plasmons – my talk at Compflu 2021

Linked is my recorded-talk presented at Compflu 2021 today (13th Dec) in the session : Active and Living Matter.

I discuss our recent work on optothermal pulling, trapping and assembly of micro-colloids under the influence of thermoplasmonic field of a single silver nanowire.

The talk was recorded on 2nd Dec 2021, so the reference on conclusion-slide is not updated.

57. Single nanoparticle driven thermoplasmonic tweezer : single-molecule SERS

We have a new paper published in Journal of Physical Chemistry Letters on “Single Molecule Surface Enhanced Raman Scattering in a Single Gold Nanoparticle-Driven Thermoplasmonic Tweezer”

Thanks to the fantastic effort by Sunny Tiwari, and excellent support by Utkarsh Khandelwal (former IISER-P undergrad) and Vandana Sharma from my group, we have been able to combine single molecule Raman scattering with a specialized nanoscale optical tweezer.

The uniqueness of this tweezer platform  is that the optical trapping process is driven by the thermo-plasmonic potential created by a SINGLE, 150nm GOLD NANOPARTICLE. Concomitantly, the same field can be used to perform single-molecule Raman spectroscopy. Kind of  “ek teer mae do shikar” strategy Smile

Using this system, not only we push the limits of optothermal trapping of a single nanoparticle (see video) at low laser powers, but also create a platform for deterministic transport of reversible colloidal assembly in a fluid.

We envisage that our nanometric plasmonic tweezer can be harnessed to trap and tweeze biological entities such as single virus and bacteria. Another possible application of our study is to create reconfigurable plasmonic metafluids in physiological and catalytic environments, and to be potentially adapted as an in vivo optothermal tweezer.

All the videos related to this study can be found on our lab’s Youtube channel : https://www.youtube.com/playlist?list=PLVIRTkGrtbrvs7BaNsaH6tjPpzLUizyMI

DoI of the published paper : https://doi.org/10.1021/acs.jpclett.1c03450

preprint version on arxiv : https://arxiv.org/abs/2109.04281

55. Kindness in science

There is absolutely no conflict between doing good science and being kind to people with whom you work, and this includes not only colleagues and students, but also administrative staff and everyone in an academic ecosystem. The below linked article makes a good case for this point.

It also derives some relevant lessons from philosophy which can be applied to academic environment. Worth reading…if you have access

https://www.cell.com/trends/cell-biology/fulltext/S0962-8924(21)00229-4

54. End-sem email to my class

Below is an email I sent to my introductory-optics class of 77 students (third-year undergraduates) on the final day of my course, which was today. Although the course was completely online, I did enjoy interacting and discussing with them on various topics on optics and photonics.

———————

Dear All,


Today is the final day of the optics course – PH3134, and I hope all of you have gained some knowledge from the online interaction we had over the past months. 


Optics is one of the most fascinating areas of science, and historically one of the oldest topics in physics. Yet, it continues to throw new surprises in contemporary research. I hope some of you will pursue research in optics and related areas. Even otherwise, do remember that optics plays a vital role in understanding and implementing various aspects of science and technology. Its relevance has remained high for centuries, and will remain so for the foreseeable future. 

I know many of you are at home, and conditions are not ideal for studies. So, thank you for keeping up your interests even during these tough times. I highly appreciate it.


An important take away for me as a teacher/researcher (from every course I teach) is that what we have discussed and studied is just a metaphoric drop in a mighty ocean of knowledge. That means there is a lot to learn for all of us. Do keep learning beyond the coursework. There is no limit for that.


Light up the world !

best wishes,

Pavan

53. Karnad’s preface to his memoir

One of the important aspects of reading a preface to a book is to know why an author wrote that book. This is one place where authors freely express their opinion on various things, and sometimes this opinion is not necessarily related to that book. For me, reading the preface connects me to the author in a better way than say, reading a review of the book, which I generally do after reading the book. Over the years, I have made it a habit to read the preface of almost any book I have come across.
In this context, recently I came across one of the most hilarious prefaces I have read. This is from Girish Karnard‘s memoir (translated from Kannada) titled : this life at play.


Below I reproduce the preface (which is by the way, available online) :

Dharwad, 1973

Aayi (my mother), Bappa (my father) and I were having lunch. My first film Samskara had won the President’s Gold Medal. My second, Vamsha Vriksha, had had a successful run and won the National Award for best direction. My latest film Kaadu was in the final stages of production. I was a Sangeet Natak Akademi awardee. And I had just been named the director of the Film and Television Institute of India. The air at home was thick with self-congratulation.

Then Aayi looked at Bappa and said, ‘And we had thought of not having him.’Bappa went red in the face. After some stammering, he managed to say, ‘That was all your idea, not mine. Why bring this up now?’ and hid his face in the plate in front of him.

I had to know more. I asked Aayi, and she explained: ‘I had three children already when I became pregnant with you. I thought that was enough, so we went to a doctor in Poona named Madhumalati Gune.’

‘And?’

‘She had said she would be at the clinic, but she wasn’t. We waited an hour and returned.’

‘And then?’

‘And then, nothing. We never went back.’

I was stunned. I was then thirty-five years old. Still, I grew faint at the possibility that the world could have gone on without me in it. For a while, I sat there unaware of my surroundings, considering the idea of my non-existence. A thought struck me. With some bewilderment, I asked about my younger sister: ‘Then, what about Leena…?’

Aayi said, somewhat coyly, ‘Oh, we had stopped thinking of all that by then.’ She burst out laughing. Bappa remained engrossed in the contents of his plate.

Had the doctor arrived at the clinic as promised, these memoirs and their narrator would not have existed. So, I dedicate this autobiography to the memory of the person who made all this possible: Dr Madhumalati Gune.

Girish Karnad

Bangalore, 19 May 2011

52. Optothermal pulling and trapping..with nanowire plasmons

We have a new paper published in the journal ‘Soft Matter’ titled : Optothermal pulling, trapping, and assembly of colloids using nanowire plasmons

When a silver nanowire is optically illuminated under certain conditions, they propagate surface plasmons. These surface electromagnetic waves not only propagate light at subwavelength scale, but also generate heat along the nanowire.

A question of interest to us: can we use the quasi one-dimensional optothermal potential of a nanowire-plasmon to trap and assemble soft, microscale matter ?

Motivated by this question – Vandana, Sunny and Dipta from my research group, performed optical trapping based experiments to show an interesting pulling and trapping effect on dielectric colloids (see video). Furthermore, by increasing the concentration of the colloids, an emerging two dimensional crystal was observed. Interestingly, the formation of this two dimensional assembly was found to be sensitive to the optical polarization at the excitation point on the nanowire.

Thanks are also due to other co-authors: my colleague Vijayakumar Chikkadi and his student Rathi for helping us to implement the particle tracking code on python.

Optical trapping and tweezing is a fascinating area of research. By adding plasmons to the mix of things, these optical effects become intriguing. Importantly, they facilitate a platform to explore questions in non equilibrium statistical mechanics including optically driven active matter…

Afterall, more is different…

DOI of article : https://doi.org/10.1039/D1SM01365C

Link to arxiv preprint: https://arxiv.org/abs/2109.09557

All videos here :

51. A case for Science + Philosophy

Linked below is an interesting article written by a Phd student.

I am glad to see a research student writing about it, and importantly it appreciates the diversity of thought, and ends well with a disclaimer.

“My background, and therefore my suggestions, are mainly rooted in the Western tradition, but I aim to continue diversifying my education.”

In my opinion philosophy is a subject that ‘many’ scientists are reluctant to entertain, and sometimes are dismissive of it. Many of the great ones, including Feynman and Weinberg have criticized it. (If I’m correct, Einstein was not one among them)

But, with the emergence of technology such as artificial intelligence, machine learning, genetic engineering and stem cell research, philosophical questions become important. Even otherwise, asking philosophical questions about any work helps us appreciate aspects such as: what it is to do work and how our scientific thought and expression interacts with the external world. In a way it is path to self realization.

I am no way dismissing the criticism of great scientists, who may have had a valid point in how philosophical enquiry is conducted. But I think it is not prudent to just discard a school of thought that lays the foundation of how humans think and evolve.

It is important for us to appreciate that Manhattan project was a remarkable scientific achievement, but the consequences had deep and disastrous societal implications. In my opinion what was badly missing there was deeper philosophical enquiry. In an essence, it was a collective human failure, where science was right, and the philosophy was wrong.

Philosophical enquiry not only helps in the evolution of science, but also helps in understanding its interface with societies. And, as we know, how science interacts with western and eastern society can have different consequences.

The case in point is the business of science tuitions in India, and the emergence of online educational platforms which are worth a billion dollars or more. Remember that the science which is been taught in these online tuitions is essentially  the same across the globe, but how the society consumes, and for what reason, is very different.
On the same footing, it also says why so many Indians are attracted to godmen and there unscientific thought processes. It may be because people may have got only the scientific, utilitarian aspect of the knowledge, but not the philosophical component. In this case the concept of critical thinking, which is by no means alien to the eastern philosophy, has been lacking  in the mix of things. As an Indian society, with the rich tradition of debate and discussion, we cannot afford to lose this culture.

This is where philosophy matters : western, eastern, and their combinations.

It is important for us, humans, to combine science with philosophy. Otherwise, science will be an ill defined vector :  large in magnitude without any direction.

https://t.co/K709wf9zAL