By Patrice Pages
December 7, 2023
Emma Xu (in 2022).
As a child growing up in China, Emma Xu loved literature and aspired to become a writer. Now a U.S. citizen, Xu, 29, is one of Forbes magazine’s 30 notable scientists under 30 . Finding her path has not been easy. When Xu became interested in math and science in high school, she didn’t know where this newfound interest would take her. But she let her curiosity and sense of discovery guide her. Along the way, she faced obstacles, disappointments, and uncertainties, but she kept at it and embraced opportunities with an open mind.
In 2009, Xu moved to the United States with her Chinese mother and American stepfather, where they settled in a small town in Texas. At that time, Xu knew very little English and had to rebuild her personal and social life in this foreign country. Since everything in school was taught in English, which she couldn’t understand, she turned her attention to math. “The numbers look the same, whether you are in China or the United States,” she thought. Her confidence in math grew.
“I was getting great grades, which fueled my interest in math. In a sense, I reinvented myself,” she says. “Later, in college, I discovered the beauty of physics and the mysteries of the universe that remained to be solved.”
Xu wanted to pursue physics, but her decision wasn’t met warmly by some members of her family and friends. Some suggested business or nursing, because there are clearly-defined career paths for these subjects that she could take after graduation. But physics? Her mother was very worried. “What are you going to do with a degree in physics?” she would ask her. But Xu was so enthralled by it that she stubbornly pursued her choice of major, even at the risk of throwing her life away, as some saw it. As it turned out, Xu did the exact opposite of throwing her life away; she found her path.
A love for nanoscience
Prof. Robert Wallace. Credit: UT Dallas.
As Xu continued on her path to studying physics, her interest gradually evolved into a passion for nanoscience, or the understanding and controlling of matter at the fundamental length scales of atoms and molecules. At that scale, matter exhibits unusual properties that differ in important ways from the properties of matter in bulk. Some nanostructured materials are stronger or have different magnetic properties than the same material in larger forms. Other materials are better at conducting heat or electricity. They may become more chemically reactive, reflect light better, or change color as their size or structure is altered.
In an effort to gain research experience, Xu knocked on every single physics professor’s door at the University of Texas at Dallas (UT Dallas) until one gave her an opportunity to work in their lab. That professor was Robert Wallace, in the Erik Jonsson School of Engineering and Computer Science, who specializes in the characterization of materials at the nanoscale. For two years, as an undergraduate student, Xu studied graphene, a sheet of carbon that is only one atom thick, in his lab.
Although Xu found this research project by serendipity, she immediately fell in love with the discipline. “On one of my first days in the lab, as soon as I saw a piece of graphene floating in a solution to be transferred for experiments, my mind was completely blown,” she says. Her positive experience in Prof. Wallace’s lab gave her the motivation and confidence to pursue other research opportunities. In the summers of 2014 and 2015, she participated in Research Experience for Undergraduates (REU) programs at Georgia Tech and UC Berkeley, respectively. After completing research projects in various labs and disciplines, she decided she would like to continue her research career in graduate school.
Xu next went to Columbia University in New York City. There, she earned master’s degrees in materials science and mechanical engineering, and is currently pursuing a Ph.D. Xu notes that her interest in nanoscience opened her mind to other disciplines, explaining why she switched majors from physics for her bachelor’s degree to materials science and mechanical engineering.
Emma Xu (right) and her advisor, Jim Schuck, examine a sample under a microscope. Credit: Columbia University.
For her Ph.D. work, Xu is working with Prof. Jim Schuck, in the Department of Mechanical Engineering, on the optical properties of materials called lanthanide-doped nanocrystals. Her work can be generally described as “using invisible light to study invisible materials.” “Invisible light,” because this light comes from infrared lasers, so its wavelength is beyond the visible spectrum; and “invisible materials,” because these materials are much smaller than the diffraction limit of light – 20 nanometers versus hundreds of nanometers – and thus are much smaller than what our eyes can see.
Among the many unique properties of these nanocrystals, the one that stands out is their ability to do “photon upconversion” – the process through which two or more photons combine to produce a higher-energy photon. This upconversion allows them to be used in many applications, such as advanced biomedical imaging and high-efficiency solar cells.
Successes and challenges of scientific research
Illustration of the chain-reaction process that underlies the photon avalanche mechanism. Credit: Columbia University.
During her Ph.D., Xu was part of a group of scientists who discovered, for the first time, a phenomenon called “photon avalanche” at the nanoscale. Like a snow avalanche, once the system reaches a certain threshold, a photon avalanche can produce a disproportionally large outcome, in the form of photons. While a photon avalanche is not a new phenomenon (it has been around for several decades), realizing it at the nanoscale and at room temperature opened up new possibilities for further research and applications. This result was published in the January 14, 2021 issue of the journal Nature and was featured on the cover of that issue, an accomplishment that is career-defining for even the most seasoned researchers.
“The significance of this discovery is profound,” Xu says. “One example is that photo avalanche enables super-resolution imaging with a simple confocal scanning microscope, at the cost of 1/10 that of traditional super-resolution microscopes, which cost about one million dollars each. More importantly, the photon avalanche process enhances the efficiency of the traditional upconversion process from about 1% to 40%, so that materials that can produce a photon avalanche could be used for a wide range of applications, from sensing to 3D printing.”
One thing Xu enjoys in her line of research is how scientists with different areas of expertise work together – a hallmark of nanoscience that has been strengthened in the United States for the past 20 years by the National Nanotechnology Initiative. This federal government effort supports researchers from various disciplines in their collaborative work to address the nation’s most pressing challenges.
For example, during one of her most recent research projects, a collaboration with scientists at the Molecular Foundry, a user facility at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory in California, Xu was tasked with embedding nanoparticles inside cells to develop a novel biomedical imaging technique. She joined forces with chemists who taught her the synthesis of the particles, biologists who showed her how cells are cultured and incubated, and an imaging expert who showed her state-of-the-art image analysis algorithms. “By getting scientists from different fields together, the different perspectives, expertise, and toolkits enable innovative solutions to be brainstormed and delivered,” Xu says.
Emma Xu aligns a laser in a lab at Columbia University. Credit: Columbia University.
Pursuing research has been rewarding, Xu says, but it wasn’t without disappointments, obstacles, and uncertainties. “To address a scientific question, you set up a scientific experiment, collect data, and then analyze these data,” she says. “Almost always, things don’t work within the first few tries; a lot of tweaking and troubleshooting is required to obtain even just one data point. It takes a long time and requires a lot of patience and persistence.” Fortunately, in a highly collaborative field like nanoscience, Xu found that she could tackle these obstacles as part of a team.
In addition, Xu says, it’s important to keep an open mind and try new things, think of new questions, or look at a problem from a different angle, something that is best done when part of a diverse group. “Sometimes you can discover new and better ways to solve scientific problems in your field by talking to and borrowing techniques from experts in other fields.”
An entrepreneurial drive
One of the opportunities that arose in Xu’s career was totally unexpected. When Xu was still an undergraduate physics student at UT Dallas, her main interest – like many students – was acquiring fundamental knowledge without paying much attention to how this knowledge was applied in real life. However, while spending her final semester interning at the Berkeley Lab, Xu was assigned to work for a startup that was part of Cyclotron Road, an accelerator designed to help bring lab inventions to the market.
While Xu was initially unsure about this departure from pure academic research, she was surprised that she enjoyed her time there. Xu met young scientists who had founded companies fresh out of their Ph.D. programs. “Until then, the research work I was doing was driven by scientific questions, which weren’t designed to solve any immediate real-world problems,” she says. “But seeing how mission-driven these young scientists and inventors were showed me the direct and positive impact that science could have on society.”
“Then, in graduate school, while I continued to do fundamental research, in the back of my head, I was always thinking, ‘How could this be used?’” Xu adds. The desire to apply her research heightened during the COVID-19 pandemic. During the lab closure and the quarantine, she found herself locked in her apartment, with a restless mind and a desire to help. Over many online discussions with her Ph.D. advisor, Prof. Schuck, they invented a novel method for viral disinfection with their nanoparticles.
The idea won Xu an Ignition Grant from Columbia University. Subsequently, Xu started her own company to commercialize this technology. In the following semesters, she took classes at the Columbia Business School to learn the necessary business skills that helped her transform a scientific idea into a product. In the lab, Xu has also continued inventing novel ways to apply her research to various applications. She now has 6 patent applications under her name.
“It’s easy to talk about science to other scientists in your field,” she says. “But when you step out of the lab and into the real world, you must develop a new set of communication skills. It’s been an interesting challenge to distill obscure scientific terms into everyday words and concepts, as I adapt to non-scientific environments and effectively communicate with non-technical audiences.”
In the process of building her own company, Xu made a wide net of industry connections, learned how to raise funding, and is now working on developing a commercialization path for her product. One stark observation she made was the difference in the way scientists and business people pitch their companies.
“Scientists tend to be cautious when talking about the features of their products because they want to be as scientifically accurate as possible,” she says. “In contrast, people with a business background are less likely to bring up the parts of their product that are still a work in progress. They focus on talking about the grand vision, maybe five or ten years down the road, which they can’t be certain about. This is quite useful for pitching to investors, although scientists often struggle with it.”
After completing her Ph.D., Xu says she would like to continue applying scientific findings in meaningful ways to address societal problems. “I would like to work at the intersection of science and business,” she says. “I want to keep my eyes open to opportunities to make an impact in the real world with science and engineering.”
Reflecting back on her experience as a college student, a researcher, and an entrepreneur, Xu has these words of wisdom for others who may want to become scientists, engineers, or entrepreneurs, but doubt their abilities or feel discouraged while trying to follow their passions: “Keep your eyes open, seize opportunities when you can, and learn to adapt to your changing environment. Also, don’t let others discourage you or label you one way or another. Be your authentic self and keep growing!”
Patrice Pages is the Communications Director (contract staff) for the National Nanotechnology Coordination Office.
SIDEBAR - Your keys to success: self-advocacy and passion
Emma Xu takes a selfie in a lab at the Molecular Foundry, a user facility at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory.
When Emma Xu first joined the physics department as an undergraduate student, she felt out of place. Many of the students and faculty there were men, with only one female professor. She longed for a community where all the physics students could hang out and support each other, so she decided to revive a student organization that had become inactive a few years before – the Society of Physics Students. She and another student brought it back to life by organizing many career-oriented and social activities, which helped her connect with more students, including female and minority students. Under her presidency, their chapter was named a “distinguished chapter” – the highest national honor in the chapter’s history.
However, outside of the welcoming community she built in school, as she ventured out and met different people, Xu often had to navigate hurtful comments questioning her ability to do what she loved most. During one of her visits to a graduate school as a prospective student, a senior Ph.D. student asked her: “Why do you want to do a Ph.D. when you are so pretty?” She was completely dumbfounded. On a different occasion, after she won a National Science Foundation Graduate Research Fellowship, some people bitterly told her that she only received it because she was a female.
“I believe most people don’t mean harm when they make those comments,” Xu adds. “Call them out, if you can.” But she also acknowledges that it could be hard to initiate these conversations sometimes. “If you need support, ask for help from people you trust.”
Even though Xu has proven her abilities as a researcher now, reflecting on her experience in the past decade as an undergraduate and graduate student, she confesses that she often felt insecure about her prospects and abilities. “Many times, I felt that I didn’t belong,” Xu says. “I was almost always surrounded by students of a different gender; they often came from academic households or at least middle-class families, whereas I am a first-generation immigrant who had to start working minimum wage jobs throughout high school and college due to financial difficulties. The implications of this are beyond financial: Many of my peers were encouraged to pursue interests related to STEM from an early age, and started engaging in scientific research as early as high school. Not only did I start later than they did, but I also needed to constantly prove myself to my family who didn’t support my career choice.”
Most importantly, Xu emphasizes that one should always keep an eye on the big picture. “Despite all the obstacles you will face, you must remain passionate about what you do,” she says. “You have to actively go after opportunities and advocate for yourself, because no one else will do it for you.”