At long last, I tamed a physics manticore.
On July 16th 2026, I held my public PhD talk: 45 minutes, then open for questions. And on July 20th, I had my closed PhD exam with the committee: one hour with short presentation, thesis questions, then general questions, a.k.a the open grill. All this was happening at the Faculty of Electrical Engineering and Information Technology of RWTH Aachen University.
My topic
The title of my dissertation is “Engineered Surfaces to Enhance Light-Matter Interactions at the Liquid Interface”. Basically, I created and studied nanostructures (somewhat like the ones in computer chips) from special materials and material combinations (metals and semiconductors). The structures and materials were designed to increase light absorption and/or scattering when light is shining on them.
This may remind you of solar panels, and there are many similarities. I focused on some emerging applications like photocatalysis for waste water treatment and hydrogen generation. There, sunlight would supply the needed energy to clean organic contaminants in water (paper here), or to generate hydrogen from water/electrolyte. In addition, some of my nanostructures were also performing well as biosensors. The enhanced light scattering was useful to amplify a laser signal, thereby allowing for the detection of trace substances in liquids (paper here).
The defence
The public talk went pretty well! I brought along some of the panels I had fabricated. In the intro, I referenced the advanced optical coatings of the Louvre pyramid and the stained glass windows of churches, in which tiny metal particles produce the different colours preceived. This was a classic exapmle of the plasmonic effect, which was central to half of my work.
Finally, for a fun demo of the increase in surface area that my nanostructures provided, I whipped out a Japanese shibori bag and showed how it can expand to more than twice its size.
However, it was still early to celebrate. I had three days to prepare for the actual exam. Most of them I spent trimming my already packed presentation to half its size. And I did spend some minutes wondering if I will survive July in a blazer. Luckily, Germany isn’t the hottest of countries.
Without revealing too much of the closed exam, I will say it went well overall, but it was also challenging to answer some questions. Especially the ones that were more about electrical engineering, and that were never remotely part of my curriculum and interests. My background spans three different universities and programs, so of course that matters, too. And the committee itself was not too familiar with me as a student and my topic in general. Typically, RWTH graduates get a head start in that regard.
The aftermath
Anyway, I passed! Right after the exam, I received a letter with my grade and instructions on how to publish my dissertation. In this waiting period, I still cannot officially use my newly earned title of Dr. rer. nat. (Doctor of Natural Sciences). Honestly, it doesn’t matter. What mattered most in that moment was the weight lifted from my shoulders, as probably anyone who has gone through it would agree. As always, there is more to this story, and I won’t go into it. If you know, you know. Let’s just have a fleeting moment of celebration, shall we?
In poured my colleagues who were kind enough to come to the faculty building on a workday and greet me. As per the local tradition, I received an elaborate doctoral hat made by my colleagues. It included figurines, a mini TV with a funny video, pictures and flowers on the rim, and some Bulgarian-Mexican references.
After, we went back to our office building where I had arranged for cakes to be delivered. We spend a couple of hours enjoying ourselves, and among the post-exam relief and the flurry of questions I got asked after, I really needed a break in the end. Happiness settled in a few days later, as I flew home to share the news with long-distance family and friends. Then, it was back to business as usual pretty quickly. Because what more is there to it?
PS
You know, I got the weird comment that I didn’t look too happy back on the day, and maybe in writing this I don’t come across as happy or thankful. I am. But honestly, it had been long overdue. Age and maturity, personal history and circumstance really matter on how you perceive the milestones. Maybe it also matters that I see my graduation as neither the final, nor the greatest achievement of my life. How brazen of me.
PPS
I will try to be useful and write about writing the thesis, but I don’t know when that would be. I will also add a link here when the thesis is finally published with online access from the university library.