The radiation man
Jan Ruschel investigates short-wave UV light sources in Adlershof
He could have done something completely different. “Way back in the day, I thought I might become an artist,” says Jan Ruschel. Quite a few brows were furrowed at his grammar school in Berlin when he chose a very particular combination of advanced courses for his A-levels. Art and physics—how does that go together?
In the end, physics had the upper hand. In addition to studying at Technische Universität Berlin, Ruschel worked for a medical technology firm that developed pacemakers for a couple of years. In late 2016, he then arrived at Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik (FBH) as a doctoral student. His dissertation was focused on the question of how the longevity of light-emitting diodes, generating short-wave UV radiation, could be prolonged. He completed his thesis in 2021, but the topic continued to be on his mind: “I can’t stop here; there are still things left to do,” is what he told himself after completing his doctorate.
While at university, his focus gradually shifted from the field of theoretical physics more towards an orientation on application: “At the end of the day, I want something to come out of what I do that benefits people.” Short-wave ultraviolet light, the so-called UVB and UVC radiation that Ruschel dealt with in his dissertation, certainly meets this requirement. UVC radiation is a bacteria and virus killer, a highly efficient method of disinfection. It even eliminates multidrug-resistant organisms that are immune to any antibiotic.
Invisible to the human eye, the UVB and UVC diodes developed by the team emit light at wavelengths between 310 and 264 nanometres. A nanometre is equal to one billionth of a metre. Just a few years ago, the radiation created by diodes made from aluminium gallium nitride was so intense that they wore out after just a hundred hours. Ruschel has found a way to prolong the longevity of the diodes to a substantial 10,000 hours. He is now investigating light sources with an even higher energy potential. They radiate at wavelengths that are shorter than 240 nanometres. Yet, they go kaput after just a few hours—and this is what Ruschel wants to change this. This would be a great achievement. Super short-wave UV light is absorbed already in the uppermost layer of human skin, which consists of dead cells. It would make it possible to kill off germs without the risk of damaging living skin tissue.
Versatility is close to Ruschel’s heart. He doesn’t like being pigeonholed: “I always tried to simply pursue my interests.” And art in the broadest sense of the world has always been one of them. “After all, I also became a musician.” For twelve years now, he has been the drummer of a Berlin-based band with the remarkable name ‘Der letzte infantile Gedanke’, which translates to ‘The Last Infantile Thought’. In some ways, says Ruschel, the name encapsulates ‘what we stand for’, namely, curiosity, fun, and being carefree, ‘childlike qualities’, one could say. “The people who book us are looking to have a good time. They want people to dance. We make the type of music we ourselves would like to hear.” It started as a hobby when he was a student, but has since turned into a type of profession. Audiences like the band. And so it lasted. Physicist, musician—is there anything else? Well, says Ruschel, he also enjoys woodworking: “I could also have seen myself become a carpenter …”
Dr. Winfried Dolderer for Adlershof Journal