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| Euplectella aspergillum Photo Credit: National Oceanic and Atmospheric Administration |
Scientific Frontline: Extended "At a Glance" Summary: Bio-Inspired Mechano-Fluidic Metamaterials
The Core Concept: Bio-inspired mechano-fluidic metamaterials are artificially engineered structures designed to simultaneously optimize load-bearing mechanical strength and smooth fluid flow dynamics.
Key Distinction/Mechanism: Unlike traditional materials that prioritize either structural rigidity or fluidic efficiency, these metamaterials utilize an intricate lattice geometry to balance both. By incorporating specific porosities—such as a 5% open area—the design guides fluid through and around the structure to suppress vortex-induced vibrations while increasing the buckling load capacity by approximately 140% compared to random structures.
Major Frameworks/Components:
- Computational Fluid Dynamics (CFD): High-fidelity simulations utilized to predict flow behavior, mitigate mechanical stress, and prevent vortex shedding.
- Finite Element Analysis (FEA): Computational models used to assess structural mechanics, physical rigidity, and force thresholds before material failure.
- Multi-Objective Optimization: An automated, high-performance computing framework that repeatedly simulates and refines geometrical designs to reconcile the competing demands of fluid dynamics and structural mechanics.
- Biomimetic Lattice Architecture: A 3D-printed, geometrically complex structure directly modeled after the biological survival mechanisms of deep-sea organisms.
Branch of Science: Mechanical Engineering, Materials Science, Fluid Dynamics, and Biomimetics.
Future Application: This optimization framework holds immediate potential for developing lightweight, high-performance materials used in aerostructures (aircraft wings and helicopter rudders), support struts for underwater pipelines, and biomedical devices (stents to restore bodily fluid flow).
Why It Matters: By proving that geometrical design modifications alone can drastically increase a structure's load capacity without adding volume, this breakthrough resolves the historical engineering trade-off between structural resilience and flow-induced vibration fatigue.
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| Bioinspired design concept and simulation-driven development of multifunctional metamaterials. Left: The deep-sea sponge Euplectella aspergillum, which inspired the lattice architecture. Center: Structural finite element analysis (FEA) and computational fluid dynamics (CFD) simulations used to evaluate mechanical and fluid-dynamic performance. Right: Example applications of bioinspired metamaterials in lightweight, flow-interacting engineering systems. Image Credit: Courtesy of Laser Thermal Lab, UC Berkeley. |
Along the vast ocean floor lives a species of glass sponge known as Venus’s flower basket. Though delicate-looking, its exterior belies an exceptionally strong, lightweight skeleton that has intrigued scientists for the past 185 years.
Now, researchers from UC Berkeley and Harvard University have taken inspiration from this marine marvel to design new metamaterials that simultaneously optimize two connected, though often competing, requirements: structural resilience and fluid management.
As reported in Nature Communications, the researchers have built an automated framework that integrates mechanical and high-fidelity fluid dynamics simulations with optimization tools, allowing users to explore complex metamaterial design options.
“Using this novel approach, we were able to optimize for both the structural and the fluidic responses of our material—something that hasn’t ever been done before in metamaterial design,” said Costas Grigoropoulos, professor of mechanical engineering and the study’s co-principal investigator with Petros Koumoutsakos of Harvard University.
“This breakthrough could potentially help industrial manufacturers create new lightweight, high-performance materials in many application domains, including aerostructures and biostructures,” Grigoropoulos said.
Understanding the Mechano-fluidic Properties of the Sea Sponge
Over millions of years, the glass sponge Euplectella aspergillum has become mechanically optimized as a deep-sea structure, living at depths below 500 meters, often for millennia. Key to its survival is the sponge’s skeleton, an intricate structure made of silica that is tough yet flexible.
“Its structure is both very lightweight and has a unique lattice geometry that allows the sponge to withstand the high water pressure and strong currents deep in the sea,” said Timon Meier, a graduate researcher in the Department of Mechanical Engineering and the study’s co-lead author. “Not only is it incredibly strong and able to carry high loads, but it also is optimized for the fluid flow it experiences underwater, guiding the flow both around and inside it to capture food particles.”
Using this architecture as inspiration, the researchers sought to generate an optimization problem that combined structural mechanics and fluid dynamics, enabling them to design a structure that optimizes both responses.
“On the structural side, we tried to create a structure that is lightweight and uses as little material as possible but that is still mechanically rigid and can carry a lot of force without failing,” said Meier. “And on the fluid dynamics side, we tried to create a structure that is not prone to any vibrations or any fluidic loads induced into the structure.”
He explained that when solid objects, such as buildings, are exposed to wind or flowing water, alternating vortices can form behind them, generating oscillating forces that may cause the structure to vibrate back and forth. This phenomenon, known as vortex-induced vibration, can lead to additional mechanical stress and fatigue. “We tried to develop a design where the flow—in this case, water—passes smoothly through and around the structure without causing vibrations,” said Meier.
To meet this goal, the UC Berkeley and Harvard teams built a high-performance computing framework that combines finite element analysis (FEA) for mechanics and computational fluid dynamics (CFD) for flow behavior with multiobjective optimization capabilities. After users specify the functional characteristics they want to optimize, the framework automatically evaluates hundreds of possible designs through repeated rounds of simulations, gradually improving the design until further iterations are unlikely to produce better results.
For verification purposes, the researchers also fabricated the optimized material using a 3D printer, and then tested its structural and fluidic responses in real environments.
“This proved to be a highly collaborative project,” noted Meier. “We worked with [mechanical engineering professor] Simo Mäkiharju’s lab for the flow measurements to confirm that our CFD simulations were indeed predicting the correct results, and with [materials science and engineering professor] Rayne Zheng’s lab to measure the mechanical properties of the final structures to validate our simulations.”
Multiobjective optimization of sponge-inspired metamaterials. Automated simulation-driven optimization reveals trade-offs between mechanical robustness and fluid-dynamic performance. Representative designs illustrate the range of solutions discovered, with FEA and CFD simulations used to evaluate structural response and flow behavior prior to experimental validation.
Image Credit: Courtesy of Laser Thermal Lab, UC Berkeley.
Optimizing to Increase Buckling Load and Suppress Vortex Shedding
Based on tests of their new metamaterial, the researchers found, on average, that the buckling load—or the force the structure can carry—increased by about 140% compared to randomly selected control structures. They also found that porosities as low as 5% could significantly reduce vortex shedding without compromising the structural stability of the system. For example, a nearly solid cylinder with helical ridges and just a 5% open area was enough to significantly suppress vibrations on the fluidic side.
“Our results were pretty impressive,” said Grigoropoulos. “We demonstrated how you can increase the load a structure can carry just by changing its geometrical design and without increasing the volume.”
This framework could someday be used to develop metamaterials for a range of applications in which flow-induced vibration can be problematic. Examples include support struts for ocean structures, such as underwater pipelines; medical stents that prop open passageways to restore the flow of bodily fluids; and aerostructures, such as aircraft wings and helicopter rudders.
According to the researchers, their framework represents both a major advancement in metamaterial design and a reminder of the ways we can learn from nature’s engineering marvels. “We’ve shown that one can be inspired by living organisms to design new, multifunctional metamaterials,” said Grigoropoulos.
Funding: This work was supported by the National Science Foundation and the Stavros Niarchos Foundation, as well as the Hellenic Foundation for Research and Innovation under the 5th Call of “Science and Society” Action—“Always Strive for Excellence—Theodore Papazoglou.”
Published in journal: Nature Communications
Title: Optimized mechano-fluidic metamaterials inspired by deep-sea sponges
Authors: Timon Meier, Sergey Litvinov, Runxuan Li, Brian W. Blankenship, Andrew Kokubun, David Hahn, Stefanos Mavrikos, Zacharias Vangelatos, M. Erden Yildizdag, Simo A. Mäkiharju, Xiaoyu Zheng, Petros Koumoutsakos, and Costas P. Grigoropoulos
Source/Credit: University of California, Berkeley Engineering | Marni Ellery
Edited by: Scientific Frontline
Reference Number: eng072126_01
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