(Nanowerk Spotlight) A carbon structure lighter than a postage stamp holds two full-sized bricks aloft without buckling, while remaining so delicate it balances on a soap bubble without breaking the film. This achievement from University of Toronto engineers demonstrates materials that match the compressive strength of carbon steel while weighing just one percent as much.
Every engineered structure must balance strength against weight. Steel provides exceptional strength through its dense atomic structure but imposes a severe mass penalty. Aluminum reduces weight but sacrifices durability. Even advanced carbon fiber composites operate within tight physical constraints. Engineers have attempted to sidestep these limitations by creating nanoarchitected materials – structures with precisely arranged internal geometries that maximize strength while minimizing mass. Yet these conventional designs invariably fail at their connection points, where mechanical stresses concentrate.
Two technical capabilities now enable a fundamentally different approach to materials design. Artificial intelligence algorithms can explore millions of structural possibilities at the nanoscale, discovering solutions that human engineers would never conceive. At the same time, two-photon polymerization – an ultra-precise form of 3D printing – can fabricate these intricate designs with features measuring just 300 nanometers.
Writing in Advanced Materials (“Ultrahigh Specific Strength by Bayesian Optimization of Carbon Nanolattices”), the research team demonstrates carbon structures that achieve compressive strengths of 180-360 megapascals – matching carbon steel – while maintaining densities of just 125-215 kilograms per cubic meter, comparable to styrofoam. This combination outperforms conventional materials by an order of magnitude.
Multi-objective Bayesian optimization for generative design of carbon nanolattices with high compressive stiffness and strength at low density. a) Illustration of process workflow. b) The top fourMBO CFCC geometries with their 2D Bézier curves. c,d) FESEM images of CFCC MBO-3 and Standard CFCC of equivalent density. (Image: Reprinted from DOI:10.1002/adma.202410651, CC-BY) (click on image to enlarge)
The team employed multi-objective Bayesian optimization to design these structures. This artificial intelligence method balances competing factors: maximum strength and stiffness with minimum density. Unlike traditional approaches that modify existing patterns, the AI explored possibilities without preconceptions. It identified unexpected geometries that distribute forces evenly throughout the structure, preventing the stress concentrations that typically trigger failure.
To build these AI-optimized designs, the researchers used two-photon polymerization to create precise three-dimensional structures from a specialized polymer. They then heated these structures to 900 degrees Celsius in an oxygen-free environment – a process called pyrolysis. This treatment transforms the polymer into high-performance carbon while shrinking the structure to one-fifth its original size.
Analysis at the atomic scale revealed why these materials perform so exceptionally. At 300 nanometers in diameter, the structural elements are so small that carbon atoms arrange themselves in nearly perfect patterns with minimal defects. The outer layer contains 94 percent of carbon atoms bonded in the same configuration found in graphene – the strongest known material. The small size prevents oxygen impurities from contaminating the structure during fabrication. Larger structures, at 600 nanometers, contain more defects and impurities, making them significantly weaker.
The team demonstrated practical scalability by manufacturing a material containing 18.75 million identical nanolattice cells. This larger structure maintained its remarkable properties, supporting more than one million times its own weight. The achievement indicates the potential for manufacturing these materials at scales suitable for real applications.
These materials could transform multiple industries. In aerospace, reduced structural weight directly improves fuel efficiency and increases payload capacity. Defense applications could incorporate stronger yet lighter protective equipment. Electric vehicles could achieve longer ranges without compromising safety. Advanced electronics could benefit from precision-printed components with improved heat resistance and mechanical stability.
The current process requires specialized equipment and carefully controlled conditions. The researchers note that optimizing the high-temperature treatment could yield even better performance. Their work demonstrates how combining artificial intelligence, nanoscale manufacturing, and atomic-level engineering creates materials that decisively outperform conventional options in both strength and weight.
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