Tag Archives: science

Feathers in my hat, and new beginnings

The 2017 spring semester was an eventful one.
Courses: MA511 😦 and ECE65900 🙂
I began with the plan that I’d finish a math course and a nanoelectronics course by Supriya Datta. The math course was a requirement, but the nanoelectronics course was something I really had to do. I had heard stories about what a wonderful teacher Professor Dutta is. For those who do not know it, Supriyo Dutta is the Father of Spintronics – the person who laid down the theoretical foundation of spin devices. I took the course and was hooked from the beginning to the end. Even though we did not have a solid background in quantum mechanics, Prof. Dutta navigated us through the treacherous currents of quantum mechanics, density functional theories, and vector algebra, and taught us the intricacies of spin transport. The quizzes were more like a formality, easy to solve if you had practiced the past papers. He designed the course to give students the necessary intuition to solve electron transport problems on their own.
I highly recommend this course to students with interest in Nanoelectronics.
The MA511 course, unfortunately, was very disappointing. The lecturer, instead of showing us the applications of linear algebra in real problems, just went on copying math notes from a notebook on to the screen. We completed the first few homeworks on time, but eventually lost interest and dropped the course.
Won the SVC Foundation Scholarship
Our group specializes in discovering and investigating the plasmonic properties of new materials – transition metal nitrides and transparent conducting oxides being a few of them. To develop films with excellent optical properties we possess our very own sputtering system. As a lot of my seniors from our group recently graduated, my colleague Deesha and I got the duty of taking care of the system. As titanium nitride is always in high demand from a lot of our collaborators, the system is always hot in demand and needs to be well maintained at all times. Being the superuser is a tough job. We have to provide samples-on-demand to our fellow labmates and our collaborators, ensure the consistency of the sputtered films, make sure that the machine is operational, and develop and optimize recipes for new materials. It’s a demanding job, but also rewarding. For instance, my close association with the sputtering system landed me the SVC-foundation scholarship, that partially covers books and tuition for a year, and pays for conference travel to any conference related to vacuum technology.
Completed my quota of tours for the Discovery Park Ambassador Program.
I had signed up for the discovery park ambassador program earlier this year. As part of the program, the Ambassadors give tours to visiting faculty and members of the public of the facilities we have here in Discovery Park. As a Birck ambassador, I gave tours of the Birck Nanotechnology Center, which houses the Scifres Nanofabrication Center. It was a really enriching experience. My audience varied from fifth-graders to full professors; so even though I was covering the same material, I had to tune down or expand my descriptions of the cleanrooms and the facilities to suit the knowledge of the audience. And the visitors never ceased to surprise me. For instance, during one of the tours, I was trying to figure out the best way to explain plasmonic tweezers to a work at home mom. The best I could come up with was, “So… when you focus light into a very narrow region, the spot begins to suck in smalls particles and hold them in position.” I didn’t get to the part where plasmonic antennae push the trapping dimensions to the sub-wavelength level. To my surprise, she responded, “Yes, so the dipole force due to the field gradient is what holds it in place. Now the plasmonic antennae enable a high field confinement, and you can trap them in a smaller space, yes?” It turned out that her husband did his PhD in optical trapping.
The following pictures are of a demo of LCDs I was giving to elementary school kids.
Nanodays 2017
Nanodays is a big annual event where all the research facilities open their doors to the public. It’s a three-day long event that features talks by men and women in science, demonstrations of science projects, and x. Representing OSA and SPIE, Deesha, Oksana, Shaimaa, and I manned a table with an assortment
of toys designed to teach people about optical phenomena. The audience this time varied from two to sixty-year-olds. I discovered that I really like explaining elementary science to students. The highlight of the day was when a cute little three year old stole a slinkie from the demonstration set from right under my friend Deesha’s nose.
Became president of the SPIE elections.
Last, but not least, both Deesha and I were nominated for executive committee positions for the OSA and the SPIE respectively, and became the presidents of the respective student chapters.
We look forward to a year full of exciting and enriching events related to optical science.
To get more information about the events and about how to join the groups, comment here, or join the following group.

2016: looking back

It has been a while since I had a chance to blog. Between classes, work, and life, it’s really hard to keep the promise I made to myself about writing regularly.

Anyway, here’s what had happened between my last post and now.

The Qualifying Exam aka The Ph.D. Lottery:

This was perhaps the biggest achievements for this year. My friends and I took the Ph.D. qualifying exams – a daunting, haunting, four-hour long exam that determines whether you are qualified to pursue a Ph.D. in Purdue.
Most of us, including myself, passed by a respectable margin.

The Soham Saha Library:

The West Lafayette Public Library was having a fundraising sale last month. You could get a bag of books For just three dollars. I always dreamed of having my own library. And thus, the Soham Saha Library was born.
I have never been an ardent reader of non-fiction and thought this would be a good time to start reading them. I ended up buying about thirty non-fiction books, and am currently reading whenever I have free time.
Some of the notable ones among the books:
– The Nobel Duel, by Nicholas Wade – a true story about the rivalry between two Nobel Laureates in Medicine. This is for inspiration.
– The Idea Factory, by Jon Gertner – It’s about the inception of Bell Labs and the brilliant innovations that took place there. It’s an interesting book on the research dynamics of one of the best Labs the world has ever seen.
– Writing Science: How to write papers that get cited and proposals that get funded, by Joshua Schimel – for obvious reasons.
If you happen to have an office at the Birck Nanotechnology Center and are walking past Room 1238, drop by and take a look. You might find something you like.


Made some new friends, learned how to kickbox, the usual random things I do.

Oh yeah, also, the Presidential election happened. But that is too much for one post.

Innovate: Soft Photonics 2016 – The Start Up Challenge – The End

So far, teams had been formed and everyone was supposed to develop and idea for a new technology that we were supposed to pitch in front of a judging panel two weeks later. All our products were supposed to have Kirigami Composites as a backbone.
Our initial idea was to make a kind of glass that would change its crystalline structure in response to a stimulus, controlling the amount of light passing through it. The idea was to use them in car windows to prevent cars from heating up when left in the afternoon sun.
After coming back from the Workshop, we began to interview people to see if there was any existing demand for our product.
Imagine that it’s a hot day, and you have left your car out in the open and went to a class. You come out, open the car door, and a wave of hot air heats you. The plastic bottle you left in the bottle holder has melted in the heat, and the car smells of heated leather. What if we could make windows that would leave the heat out but let light in? If your answer is yes, you are our target.
The same window could also be used in buildings to keep them better insulated by controlling the influx or dissipation of heat. Also, since we were controlling the flow of light through the windows, they could also be used for adjustable privacy windows, that prevent outsiders from seeing through building windows.
We started off by interviewing potential customers for our product. And this is where we hit our first bump. While people were frustrated with cars getting heated up in the sun, there was a solution that was fairly easy to implement. Peoples could leave their windows slightly open to let the heat vape out. Also, we were not very sure how much of the heating was taking place just through the windows, since the entire metal body of the car would start heating up in the sun. Beside that, an initial survey showed that people were not willing to pay more than 10-20 dollars for a product. So changing the glasses in cars was out of the question.
The same went for houses. While real estate developers were interested in getting a new kind of glass that would make their buildings more environment friendly, building owners were not so keen on changing the entire window paneling to same a few bucks on electricity.
Well, what next? We decided that we’d put our efforts into developing a film that would be applied to windows instead. We ran subsequent interviews with homeowners, real estate developers, and car owners. This time, people were more enthusiastic about our product, which would not replace a technology that already exists, but augment it.
Next, we looked up potential competition. We saw that Corning Glass was already selling auto-tinting glass panes for offices and houses to save power. However, this technology has a drawback. It would need someone to completely change all the glassing from the windows.
Polytronix is another company that works with something similar. They make films that change their transparency in response to a current passing through them. But they are active devices and consume power, hence won’t really save power for buildings that use them.
So in the end, the final product was to create a film that could change its transparency by changing its mechanical structure, radiate heat out if needed, and automaticaly decrease the transparency of glass, giving you privacy.
We presented our idea in a skype meeting with a panel of judges, along with other groups.
  1. The Matrix – They presented a technology idea to integrate a pressure sensor at the tip of surgical equipment that would help doctors to get a feel of how much pressure they are applying to a tissue during surgery.
  2. Kiragucci – They proposed colour changing fibers to design tents that could blend into their surroundings.
  3. Four photons – They proposed a high precision optical blood pressure monitor.
  4. Synergy Energy Solutions – They started off with the same idea as us, but went on to focus on controlling the light transmission in greenhouses, using colloidal particles flowing through microfluidic channels.
Finally, the winner was – Synergy Energy Solutions.
Overall, it was a wonderful experience looking at how product development works, and how the idea has to be changed and updated at every step until it finds a potential user. And it was a privilege to see how creative people isolate problems and find solutions to them.
In the end, it was a wonderful experience.
But now that it is over, it’s time to get back to real research.
Link to our presentation: LumiVeris

Where Newton’s Third Law doesn’t work

In the last post, I talked about some of the basics of Newton’s three laws of motion.
Reiterating them.
1. The first law is about a body’s reluctance to change its state of motion – If it’s not acted upon by an external force, a body undergoing uniform motion will moving, and a body at rest will remain at rest.
2. The second law is about how a body reacts to a force – The rate of change of momentum of a body is proportional to the force acting on it.
3. The third law states that for every action, there is an equal and opposite reaction.
Here’s an instance, however, where the third law does not apply.
For this bit, you’ll need a little bit of background in electromagnetism.
A moving charge creates a magnetic field around it. The direction of the field is given by the right hand rule. If the thumb of your right hand points along the velocity of a positive charge, your fingers curl along the direction of the field.
Right hand rule
A charge moving in a magnetic field experiences a force that is proportional to the charge of the particle, its velocity, and the magnetic field.
F = qv x B.
The direction of the force experienced by the particle can be given by Fleming’s Left Hand Rule, depicted below. If your forefinger points along the direction of the field a positively charged particle is moving through, and your middle finger in the direction of motion , your thumb points along the direction of the force experienced by the charged particle.
Fleming's left hand rule
Now look at this figure where two positive charges are moving in directions perpendicular to each other.

2016-02-20 06_54_02

The red charged particle (Particle 1) is producing a field B1. The blue particle (Particle 2) is moving through the field upwards. As it does so, it experiences F21, which pushes it to the right side, as shown by the red arrow.

According to Newton’s third law, Particle 1 should also feel a magnetic force F12 to the left, created by Particle 2. However, since the field produced by Particle 2 (B2) is zero at point 1, Particle 1 feels no force acting on it when it is directly underneath Particle 2.

So, F12 = 0.

Newton’s Third Law does not apply.

If you want to dig deeper and understand why momentum is still being conserved in this scenario, you can mull over reference 3. It’s explored there in great detail.

[Note: I am omitting the Coulomb forces the particles are exerting on each other. They are equal and opposite. It’s the magnetic forces that aren’t obeying Newton’s Third Law.]


  1. Fig1:https://www.physics.rutgers.edu/ugrad/227/L15%20Magnetic%20Field%20of%20Currents%20Biot-Savart.pdf
  2. Fig2: http://www.bbc.co.uk/schools/gcsebitesize/science/triple_aqa/keeping_things_moving/the_motor_effect/revision/3/
  3. http://physics.stackexchange.com/questions/138095/newtons-third-law-exceptions


Newton’s Three Laws of Motion – A fun exercise

Let me start with an update on my PhD status. Obvious from the frequency of my blog posts, I have been extremely busy with my projects and coursework. But I am glad to say that, thanks to group mates I can trust and talented lab partners I can rely on when I’m in trouble, things could not have been more productive. And honestly, I don’t mind being under a lot of pressure as long as I am being productive.
Okay, now for the topic of this post. I have been wanting for a long time to write about something that’s very basic in physics – Newton’s Laws.
Before I go into detail, here’s a simple question you can ask your friends. And try to answer it as fast as possible, like, in under ten seconds. Come on, you are a smart guy! You shouldn’t take any more time than that.
While you are asking the question, make sure you contract your arm, and make a throwing motion, providing a visual aid for the innocent victim. If you are lucky, you’ll probably make them give you a wrong answer.
It seems like an easy enough question, but you would be surprised how many get this wrong. Of course, the question lacks a lot of detail. Where in space is the object? How far are the nearest bodies that might exert a force on the object?
The object is not going to slow down. Everyone gets this bit right. There’s no air resistance. So nothing slows the ball down. [Unless your time scale is over millennia and the ball loses its momentum bumping into tiny space particles floating around].
Now, why does the ball not speed up? You did exert a force on it that caused it to accelerate, and as I have established before, there’s nothing there to slow it down, right?
Well, it did accelerate as long as your hand was pushing it forward. But as soon as the ball left your hand, it did not have any force pushing on it anymore. So, it would move in a straight line in a constant speed.
But what about the third law? For every action there is an equal and opposite reaction. So if there is a reaction force, why don’t the two forces cancel each other out and the ball remain at rest?
That’s because the action and the reaction force don’t act on the same body. The reaction force exerted by the ball acted on your hand, and decelerated it, as your biceps tied to pull your hand forward. Since the force by the ball was decelerating your hand, it could not cancel out the force your hand was exerting on the ball.
Sweet. So far we’ve covered high school level physics. But honestly, I have seen Olympiad competitors, engineering students, and even PhD students mess up this simple question. Just needs a little misdirection.
Now, after we have kind of established Newton’s laws and their ‘infallibility’, in my next post, I am going to give you an example where Newton’s third law does not seem to work.

A reason to pursue science as a career

There is a weird old story in Hindu Mythology.
Indradyumna, the son of Bharat, was the greatest man on Earth. It was well known that there was no one to match his “Dharma-Swabhaav”, his righteousness. As a consequence of his good deeds, he ascended to Swarga (Heaven). There, for thousands of years, he enjoyed the limitless luxuries he earned as a consequence of his good deeds. But one day, Indra, the king of the lesser Gods, told him, “O King, you have done immense number of punyaas (good deeds) in your life and as a result you were here for a very long time. The time on earth past so much that now no one remembers any of your good deeds and hence it is time for you to leave heaven”. [Now, why the God king used such a long convoluted way of saying “Time’s up!” escapes me, but that’s pretty much how dialogues in most religious texts go.]
The rest of the story is about Indradyumna’s quest to find the one creature on the planet that remembered his good deeds.

Note to self: Must find out why a lot of famous Hindu are painted blue.

The crux of the story had always struck me as a kid. That even the deeds of the greatest man on earth are great as long as they are remembered.
There are more several ways to be remembered in history. Becoming a great philanthropist like Mother Teresa. Writing great work of literature like Shakespeare.
But for me, a great way to survive would be to make a scientific discovery.
Nothing underpins the impact of making scientific discoveries more than the story of Archimedes.  You know his story about him running in his birthday suit, crying ‘Eureka.’ If you had a good science teacher in your highschool, you might have heard him tell you that it was something about dipping things in water to determine their purity. But you need to delve a little deeper into the story to appreciate the timelessness of an epic scientific figure.

He probably wasn’t bald!

Archimedes died during the siege of Syracuse, during the second Punic War. The name of the war sounds unfamiliar, right? The Punic War took place between the Romans and the Carthaginians. Much like the first and second world wars, the battles saw great strides in scientific discoveries, with all the participants employing cutting edge war machines and military strategy to outclass their opponents. Over a hundred thousand soldiers died in the battles alone, in a war that lasted for seventeen years.
It is one of the battles that shaped human history as we know it. For one thing, if the Carthaginians had won the war, Jesus might not have been born. If you still are not convinced about the epicness of the war, just take a look at the map of the participating nations.
Second Punic War

The original “Second World War”

The fact of the matter is, the Second Punic War was at a time, as significant to human histories as the World Wars are to us. However, we barely remember it.
But we remember Archimedes and his naked run in the streets of Syracuse.
So it is not a far off bet to guess that one day, humanity will forget about the First World War, but remember Maxwell and his equations; we’ll forget about Hitler and the Second World War, but remember Albert Einstein’s theories.
And that is a compelling reason to pursue science as a career, for the remote chance that we might find something that lasts through humanity’s history.
Also, the work hours are nice.
Note: The post was inspired from Professor Evgeni Narimanov’s first lecture in his course ECE60400: Electromagnetic Field Theory. This was undoubtedly one of the best classes I have ever taken.
1. Wikipedia articles – Indradyumna, Second Punic War, List of battles by casualties.
2. Cartoon: https://speechdudes.wordpress.com/tag/archimedes
3. Map:  From the book Atlas of Empires by Peter Davidson.

About this blog

I started this blog as a collection of snapshots of my PhD life, with my short term and long term goals, achievements, ideas and epiphanies, major life events, and basically anything else that is related to my research life.

Here’s a tentative list of what this blog will comprise:

  1. Literature review: I will summarize interesting papers I review in the course of my PhD.
  2. Tutorials on electromagnetism and related problems.
  3. My thoughts on recent events that occur in the scientific community.
  4. Experiences in the cleanroom.
  5. Announcements on upcoming events – conferences, symposia, and workshops.

For tutorials, I will try my best to follow a simplistic approach, keeping jargons and complex mathematics to a minimum. I’ll take the same approach for any journal article I summarize and review.

This is not a complete list, and I am going to keep updating it as I get new ideas for posts.