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In 2005, the Faculty of Science was established at Utrecht ľ�ϸ���Ӱ��. In that same year, Utrecht researchers published that finally provided experimental evidence to answer a key question in materials research: do crystals become stronger or weaker when they are formed around impurities?

Previous simulations had predicted that contaminated crystals would be stronger, but the Utrecht experiments showed the opposite effect. A major breakthrough, which was made possible partially by a failed lab assignment by first-year students. An unforgettable experience for both students and researchers, scientifically and personally.

Inexperienced lab workers

Looking back twenty years, it is not the Science publication itself that stands out the most for co-author Willem Kegel, who was then an associate professor in Chemistry. “What I like most about this paper is that two of the authors were first-year students at the time. Around that time, we had a significant drop in enrollment, with only about thirty first-year students instead of the usual hundred or so. That meant we had more time for individual guidance and were able to  organize an intensive three-week, full-time research project in the first year.”

What I like most about this paper is that two of the authors were first-year students at the time

Two of those first-year students were and Hans Scherff, newcomers in the lab. The first step of their project: create small colloids, particles ranging from a few nanometers to micrometers in size. “It was supposed to be simple,” Esther recalls. “Everyone managed to do it. Except us! Our particles became way too big. We never figured out exactly what we did wrong, but I have my suspicions. I’m very precise, but Hans is much more pragmatic. At one point, for example, he casually – splat! – dumped the necessary stabilizer straight into the mixture instead of weighing it separately in a dish first. Maybe that’s where it went wrong.”

A happy accident

Remarkably, it was precisely these oversized colloids that led to the Science publication, Willem explains. “We immediately thought about the crystal formation study. The previous simulation results had been inconclusive. Our students’ large particles were perfect for mimicking impurities in a so-called colloidal crystal, which is made up of smaller particles. This allowed us to use a microscope to see the effects on crystal formation.”

Initially, Esther and Hans had no idea that their lab work would contribute to a significant discovery. “We were mainly frustrated that our experiment had failed,” says Esther. “But our supervisor, Volkert de Villeneuve, ran some extra tests that evening and came back excited the next day: this actually has huge potential! We revised our research plan together and were able to successfully finish our lab project after all.”

High-quality and newsworthy

The researchers observed that particles did not arrange neatly around impurities, leading to fracture lines in the material. It was ultimately Henk Lekkerkerker, then a professor of Physical Chemistry, who suggested submitting the paper to Science. Willem explains, “The fact that our paper was accepted was not only about the quality of the research. Luck also played a role. Science receives an overwhelming number of high-quality submissions. A paper also needs to be newsworthy: it has to align with current trends and also present something unexpected. Materials research was – and still is – an important research theme, and we happened to stumble upon an unexpected result.”

The ultimate relationship test

Looking back, the research project was a perfect learning experience, Esther says. “It was incredible to experience the reality of doing academic research so early on. And for Hans and me, it was extra special. We had just started dating, and spending three weeks together in a lab was the ultimate relationship test. We passed with flying colors: twenty years later, we’re still together.” In 2013, she transitioned from academia to industry, but she remains in touch with her former mentors. “Volkert often sends me congratulations on my birthday. And last year, I sent Henk a birth announcement for our youngest son.”

Loads of energy

From the seventh floor of the Kruyt building, Willem looks out towards Utrecht’s skyline: green fields, the highway, and the city beyond that. “I often stand by the window to think. I feel lucky that I can see the Dom Tower from my office. I’m originally from Rotterdam, but I came here to study and never really left, except for a two-year postdoc in the U.S. and a few sabbaticals. I’ve always loved it here.”

I’m originally from Rotterdam, but I came here to study and never really left

A year after the Science publication, Willem was promoted to full professor. A coincidence? “Back then, publishing in top journals was almost a requirement for significant career advancement. This was my second Science paper, and it could certainly have helped.” He later became head of department and then director of education for Chemistry. “Teaching has always been a passion of mine. In three years, I’ll have to retire. But I want to keep going as long as I can. Working with students gives me loads of energy.”