Xi Chen's latest research idea came to him in the produce aisle—in the form of an acorn squash, to be exact.
Intrigued by why certain fruits and vegetables have particular shapes, Chen—an associate professor of engineering mechanics at the Fu Foundation School of Engineering and Applied Science—wondered, why does an acorn squash, no matter its size or ripeness, always have 10 ridges? Why does a Korean melon have 10, too? Why do bell peppers consistently range between four and six ridges?
Not altogether discounting biology, Chen proposes that a basic engineering principle gives certain vegetables and fruits their distinctive shapes. A structure under pressure, explained Chen, will bend, or in engineering terms, buckle. In the case of the acorn squash, its skin grows faster than the core, but to remain adhered to the core the skin buckles into these familiar ridges.
"It's always interesting to figure out a simple principle behind a seemingly complicated phenomenon," said Chen.
This is how Chen, 32, approaches much of his research, which focuses on mechanobiology. Known for inventive research methods, Chen recently received the Presidential Early Career Award for Scientists and Engineers, the highest honor given by the U.S. government to young scientists. Chen was one of 20 researchers nominated by the National Science Foundation (from a pool of 26,000) and honored at a White House awards ceremony Dec. 19.
His fruits and vegetables research enabled him to experiment with ways to control the mismatch damage that occurs in thin-films, material so tiny as to be nano-scale. Here, the film was the vegetable skin whose growth is mismatched with that of the underlying core, causing spontaneous wrinkling. Chen's research has been applied to low-cost, efficient fabrication of the components of micro-electronics and sensor skins for robots and medical prosthesis equipment. He also pioneered a new class of materials that addresses challenges in energy and the environment.
Chen's fascination with mechanics is seemingly limitless, spilling over into physics and biology. Rather unusual for someone who never intended to pursue a career in engineering mechanics in the first place. As a youngster growing up in China, he loathed the subject.
Born in Suzhou, China, Chen learned English while in high school, at the age of nine. At 13, as a freshman at Xi'an Jiaotong University in Shaanxi, he felt pressured to major in mechanics by the department chair. Despite an abundance of mechanics students, the subject was taught in a lifeless manner, he said, with no real-world examples.
But Chen stuck it out and got his master's at age 21 from Tsinghua University in Beijing, then went to Harvard University for his Ph.D. It was there, while a research assistant, that Chen began to see the vast possibilities in engineering mechanics, for which he credits his former thesis adviser, Professor John Hutchinson. "He used wide examples to make me see why mechanics is interesting," Chen said. "That completely changed my view of mechanics."
Encouraging Chen to talk to professors in the physics, chemistry and even anthropology departments, Hutchinson trained him to apply the basics principles of mechanics to alternative areas. "It was obvious from the start of his studies at Harvard that Xi had the prior training, the motivation and the ability to stand out as a researcher," said Hutchinson, professor of engineering and applied mechanics. "I'm honored that he credits me with broadening his perspectives and interests. I think that can primarily be chalked up to the fact that mechanics has a key role to play in a vast range of engineering problems and physical phenomena."
Now Chen tries to instill that same drive and enthusiasm in his own students. This summer, he will teach a younger audience how to think unconventionally in an engineering program offered to Harlem high school students through Columbia's Double Discovery Center.
Chen, mindful of his own experience, knows that students can shy away from science. "They can be intimated by the lab with its fancy equipment and by looking at the detailed equations on the board," said Chen. "I'm trying to explain science using very simple principles. I hope this motivates and encourages some of them to pursue science and engineering as a career."
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