Playing with materials, in a way, has become her life’s work: Gradečak now studies materials that could help to improve energy harvesting and conversion, or processes that could improve the properties of materials used in various industrial and high-tech applications.
Her parents always put a strong emphasis on education and a strong work ethic, Gradečak says. “They really were role models,” she says, and she learned early “that hard work and effort really pays off.”
But her life took a sharp turn when the situation in her homeland began to change after the collapse of Yugoslavia. “I had a very nice childhood,” Gradečak says, “until war broke out in 1991, in my second year of high school. My parents had to move, and they basically lost everything that they had built, and they had to start from scratch.”
The lessons of those events made a deep impression, she says. Gradečak was starkly confronted with the fact that “there are many things that happen in life that you can’t control. But the things you can control are your own actions. I thought about the fact that I wanted to make this world better for my family, and for the world in general.”
“The best way I could think of to do that was to excel in what I’m doing,” she adds. “I was passionate about science, and about engineering. I thought if I want to have an influence in the world, I have to be very good at what I’m doing.”
Gradečak’s interest in science was stimulated by her experience attending an astronomy summer school during her high-school years. “We were exposed to scientific methodology and creative ways you can ask relevant scientific questions, design science experiments, and interpret the results. That was really the starting point for me,” she recalls.
Later, as an undergraduate at the University of Zagreb, Gradečak continued to pursue her interest in astronomy. Together with classmates, she organized an expedition — raising funds and designing and building equipment — to observe the annual Leonid meteor shower from a vantage point in Mongolia, where the shower was expected to produce its strongest outburst in decades. Sure enough, the display was “really incredible, you could see meteors almost every second,” she says. The expedition was designed to study the sounds generated by the meteors; Gradečak’s results ended up being published in a scientific journal.
That reinforced her interest in physics and astronomy, Gradečak says, but “one thing that was missing for me in astronomy was the component of experiments. … I really liked it, but I always felt like an observer.” After all, one of the things that had drawn her to science in the first place was that “you can set up a hypothesis, design an experiment, and eventually prove or disprove it and move forward.”
That interest in hands-on experimental science propelled her toward condensed matter physics, she says. “There, I really felt I could play with materials,” she says. “I could work with something I designed on my own, and with the discoveries I make I can modify the materials with completely new properties.”
Gradečak went on to earn her doctorate at EPFL in Switzerland, along with her boyfriend — now her husband — Slaven Garaj, who she had met at the astronomy summer school. While at EPFL, she traded telescopes for electron microscopes: “Instead of far away, I was looking at the nanoscale,” she says. She began studying gallium nitride, a promising semiconductor that was just starting to be used in devices such as light-emitting diodes, or LEDs, and high-frequency transistors. Her thesis described how defects affect the material’s properties — in some cases, actually making it more efficient.
Gallium nitride, and the techniques used to study it, have continued to be central to Gradečak’s career, she says.
She was offered a postdoctoral fellowship by the Swiss government that allowed her to pursue her work anywhere in the world. She chose to go to Harvard University, where she worked on nanostructured materials. There, she found herself at the cutting edge of new discoveries about how gallium nitride’s properties could be tailored by changing the size and shape of the material — such as by shaping it into nanowires.
“It really opened up an entire new field of research for me,” Gradečak says. In 2006, she joined MIT’s Department of Materials Science and Engineering, earning tenure this year.
These days, Gradečak’s focus is on tailoring “nanomaterials on demand,” with precisely tuned properties to match the needs of specific applications, such as energy production, energy storage, or LED displays. “We have the tools that enable us to really look into the materials and test their properties in situ,” she says, such as electron microscopy and cathodoluminescence, which makes it possible to study materials down to the arrangement of atoms within them.
Using such techniques, Gradečak continues her pursuit of the ultimate goal that led her into science and technology in the first place: how to make the world a better place. Now, her focus is on making better materials that can help to solve problems by, for example, generating electricity more economically, or using it more efficiently. “It’s something I’m really passionate about,” she says.