Nanoarchitectures and 3D printing – new materials with high strength and low weight

Researchers at the University of Toronto and the Korea Advanced Institute of Science & Technology (KAIST) have used machine learning to develop nanostructured materials that combine the strength of steel with the lightness of polystyrene. The work, published in Advanced Materials, shows how advanced algorithms and 3D printing can help optimize these materials. This development could enable significant advances in aerospace and other industries.

“Nano-architected materials combine high performance shapes, like making a bridge out of triangles, at nanoscale sizes, which takes advantage of the ‘smaller is stronger’ effect, to achieve some of the highest strength-to-weight and stiffness-to-weight ratios, of any material,” says Peter Serles (MIE MASc 1T9, MIE PhD 2T4), the first author of the new paper. “However, the standard lattice shapes and geometries used tend to have sharp intersections and corners, which leads to the problem of stress concentrations. This results in early local failure and breakage of the materials, limiting their overall potential. As I thought about this challenge, I realized that it is a perfect problem for machine learning to tackle.”

The materials, known as nanolattices, consist of tiny components measuring just a few hundred nanometers. These carbon structures are arranged in complex 3D geometries to achieve exceptional strength and stiffness values. Machine learning was used to optimize the arrangement of the nanolattices to better distribute stresses and increase structural efficiency. The team used a Bayesian optimization algorithm that relied on 400 simulated data points to identify optimal geometries. This small data base was possible due to the high quality of the simulations, which were based on finite element analysis.

The prototypes were manufactured using a two-photon polymerization 3D printer, which enables printing at the micro- and nanometer scale. These newly developed structures doubled the strength of previous designs and withstood loads of 2.03 megapascals per cubic meter per kilogram of density. These values far exceed the performance of titanium.

“We hope that these new material designs will eventually lead to ultra-light weight components in aerospace applications, such as planes, helicopters and spacecraft that can reduce fuel demands during flight while maintaining safety and performance,” says Filleter. “This can ultimately help reduce the high carbon footprint of flying.”

These materials have a wide range of applications. In aviation, they could help to make aircraft lighter, reduce fuel consumption and cut CO₂ emissions. Future research will focus on scaling up production and developing further designs to enable the application of these technologies on a macroscopic scale.