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From Colorful Droplets to 3D Printing, Chemist Lauren Zarzar Redefines How Materials Work

Lauren Zarzar
Lauren Zarzar, Ph.D. Photo courtesy of Penn State.

If there’s anything AAAS Milligan Mason Award winner Lauren Zarzar aspires to change, it’s the way creative thinkers often dismiss careers in science, haunted by the grade school rigors of balancing chemical equations or reciting the periodic table.

“We need the most creative people in science,” says Zarzar, an assistant professor of chemistry at Penn State University. “It’s not just about memorization and regurgitation. It’s about creativity and looking at problems in new ways.”

Zarzar’s own research serves as an example, harnessing both imagination and innovation to peel back the curtain on how the world works.

In a publication featured by Nature in 2019, she explains how tiny, clear water droplets on a transparent surface exposed to white light can produce dazzling colors – a sort of natural light show.

In fact, you don’t need a laboratory to recreate the experiment. Shine a light through a Tupperware lid covered in condensation and you might see the edges of the drops glow with vibrant hues depending on your angle of viewing.

Until Zarzar’s work, this effect had never been explained at this scale. “It’s sort of humbling,” she says. “You think you know things, but sometimes you actually don’t. It’s a good attitude to have as a scientist. It’s okay to be naive, not know what’s happening and ask questions.”

The results of her research further the understanding of “structural color,” which is produced by light’s interactions within a clear object’s geometry. In contrast, pigments and dyes inherit their colors by absorbing specific wavelengths of light while reflecting those that we see.

While resting on a surface, the water droplets form dome-like structures, in which the entering light bounces around multiple times, colliding and interfering with itself until a rainbowlike array exits in many different directions.

This color-shifting phenomenon – known as “iridescence” – is visible on the surface of soap bubbles.

“It’s like a mirror but only for certain light angles,” Zarzar says. “It’s not truly a mirror – water is clear – but at certain angles of the light hitting the water you’ll get reflections similar to a mirror.”

A related technique is already used in the manufacturing of decorative film which produces a holographic pattern using “nanoscale” structures not visible to the naked eye.

Zarzar’s work explained how the effect could be achieved in larger structures – such as droplets or polymer materials – perhaps making these films easier and cheaper to manufacture with a diversity of iridescent colors. Recently, Zarzar received funding from the National Science Foundation to explore the commercial applications of this research. Some use cases may include decorative coatings on wrapping paper, automobile paint, or anti-counterfeit markings on currency.

In her latest projects, Zarzar focuses on laser-direct writing, a process that creates solids by aiming a laser into a chemical solution. Her goal is exploring and improving 3D printing capabilities with oxides and metals at microscale.

The laser works “like a pen,” Zarzar says. At the focus of the laser, a metal oxide material is formed. After stacking layers of these synthesized solids, precise three-dimensional structures can be constructed on a very small scale. Perfecting this technique, still in its infancy, has potential applications for improving the manufacturing of tiny, metal components used, for example, in electronics.

In 2021, Zarzar added to her accomplishments, becoming a recipient of the AAAS Marion Milligan Mason Award, which recognizes her leadership and outreach in her field.

The Mason Award, which grants $55,000 to early-career female scientists, commemorates the late chemist and AAAS Member Marion Tuttle Milligan Mason, who wished to support the advancement of women in the chemical sciences and honor her family’s commitment to higher education for women.

Though strides have been made in recent years, women entering STEM careers, including those in academia, are still underrepresented. Zarzar credits her parents and several female academic advisors for advancing her pursuits.

“My parents were very supportive,” she says. “They told me to find what you’re passionate about and do your best at it. That’s an attitude I’ve tried to live by.”

Zarzar says she also had an engaging high school teacher who explained the subject of chemistry as a foundational gateway to other scientific fields. It struck her imagination and propelled her interest in the subject through college. After completing bachelor’s degrees in chemistry and economics at the University of Pennsylvania in 2008, Zarzar earned her doctorate in chemistry at Harvard in 2013. She completed postdoctoral work at MIT before joining the faculty at Penn State.

In the classroom, whether virtual or in-person, Zarzar tries to inject real-world examples to motivate and excite young minds – especially the creative ones.

“All scientific research is discovering things nobody had ever thought of before, which is inherently creative,” she says. “This is what’s going to be pushing science forward, and we need creative people to be interested in science.”

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Lauren Boyer