Sea urchins may hold key to lightweight engineering materials

Sea urchins may hold key to lightweight engineering materials

In the ongoing search for strong, lightweight materials, researchers are looking at an odd source – sea urchins, which have spines made of chalk, a generally brittle substance.

The highly complex three-dimensional structure of sea urchin spines that is 70 to 80 percent porous creates a stable and strong structure. Studying the sea urchin is part of a $540,000 National Science Foundation grant being investigated by Ling Li, assistant professor of mechanical engineering in the College of Engineering.

By using design rules gathered from studying biological systems and inputting those rules into the design of bio-inspired lightweight ceramic materials, Li said he hopes the information can be applied to creating lightweight panels and other components.

“I can see this information being applicable to panels, structural support, and armor to provide impact and blast protection,” said Li. “The design is very damage-tolerant and does not fail catastrophically.” As the current work constitutes fundamental research to uncover the design principles of a biological material system, Li said his team could only look forward at the potential for applying the lessons learned for innovative bio-inspired materials.

“We want to understand how nature designs lightweight materials with brittle components and we are trying to understand the 3-D architecture of the sea urchin spine’s structure to see if we can determine how the structure helps achieve high strength and damage tolerance given the inherent weakness of the chalk it’s made from,” said Li.

Working with co-investigator Yunhui Zhu, an assistant professor with the Bradley Department of Electrical and Computer Engineering, the team will use a synchrotron tomography technique and mathematical tools developed by the Argonne National Laboratory to obtain high-resolution 3-D volumetric data to determine how the porous network is designed in terms of connections, arrangements, and orientation.

“The project is based on characterizing and understanding the internal structure of the sea urchin spine to find out why it’s so strong,” Li said. “Sea urchin spines have been shown to perform similarly to the best ceramic cellular materials people have made in the lab in terms of relative strength.”

One of the differences between man-made and natural cellular structures is the non-symmetrical formation of cellular struts and nodes which also vary in thickness and orientation gradually at different locations.

“Most of our current 3-D printed materials are based on idealized geometries such as cylindrical beams with a constant cross-sectional area, which may contribute to catastrophic failure behavior in some printed ceramic solids,” Li said. “Looking at sea urchins we see curved morphologies in stark contrast to 3-D printed structures. By studying these we hope to learn how to input these natural designs into our laboratory-created materials.”

Li said that this NSF award seeks to develop methods for acquiring, handling, processing, extracting and evaluating the computational data for a hierarchical structure in order to integrate the information with 3-D data and testing, to develop engineered cellular materials.