Chen Wins PECASE Award

Xi ChenAssociate Professor Xi Chen of the Department of Civil Engineering and Engineering Mechanics has taken fruits and vegetables off the table and put them in the laboratory.  The fruits of his research resulted in his being named a recipient of the highest honor that any young scientist or engineer can receive in the United States, a Presidential Early Career Award for Scientists and Engineers (PECASE). 

Chen (right) was among 67 researchers nationwide, and one of 20 National Science Foundation (NSF) nominees, to receive this national award. It was given “in recognition for his outstanding research involving mismatch damages in thin-films and nano-scale self-assembly,” and was presented at special White House ceremonies in December by then-President George W. Bush. He is shown above, center, with NSF Deputy Director Kathie Olsen, left, and Science Advisor to the President John H. Marburger III.

Chen and his research group, using engineering mechanics principles, have provided the first explanation of why some fruits and vegetables, such as cantaloupes, pumpkins, and bell peppers, are characterized by distinctive skin patterns. “Many spheroidally-shaped fruits and vegetables have distinct ridges, ribs or mottled patterns,” says Chen.

“For instance, the Korean melon, ridged gourd, small pumpkin, and acorn squash have 10 equidistant longitudinal ridges that run from stem to tip; a large pumpkin has about 20 ridges. Striped cavern tomatoes and bell peppers have four to six ribs that characterize their unique appearances, while cantaloupes show a reticular morphology that mixes ridged and latitude patterns.”

Chen’s group has come up with an explanation for these ridged characteristics by using the buckling principles of engineering mechanics. “The distinct appearances of some natural fruits and vegetables are governed by simple mechanical principles. Because of mismatched deformation between the shell (skin) and core (flesh), the excessive growth of the shell could induce buckling and serve as a template for subsequent growth,” he says.

Chen believes that this research is also highly relevant to a number of systems in animals and cellular biology, despite the many biological and biochemical factors that also are involved. “Our work implies that what might be thought of as merely a work of nature is, in fact, a result of simple mechanical principles.”

In addition to research on ways to control the mismatch damage of thin films, Chen explores mechanobiology, nanomechanics, nanoindentation, mechanical self-assembly, small material structures, and multi-scale and multi-phase computational mechanics. He also has pioneered new materials that absorb energy.  He joined Columbia University in 2003 after receiving his PhD and postdoctoral training from Harvard University. He has published more than 130 peer-reviewed journal papers, many of which were in high-impact journals and several were featured as cover stories