Unlocking the Future: Revolutionary Auxetic Materials Set to Transform Design!

auxetic material design algorithm

Breakthrough Algorithm Transforms Auxetic Material Design for Future Innovations

Auxetics, which expand when stretched and contract when compressed, defy conventional mechanical behavior. Researchers at the National Institute of Standards and Technology (NIST) have now streamlined the process of harnessing these unique materials.

Envision pulling the long ends of a rectangular piece of rubber. Traditionally, it should become narrower and thinner. But imagine if, instead, it expanded in both width and thickness.

Conversely, when you push in on those ends, what if the rubber became narrower and thinner?

These counterintuitive materials, known as auxetics, exist and possess a range of distinctive properties. They are ideal for applications such as sneaker insoles, bomb-resistant structures, car bumpers, and advanced textiles.

Despite their remarkable potential, auxetic products have been slow to enter the market. Researchers at NIST and the University of Chicago are working to change that.

In a recent study published in NPJ Computational Materials, the team revealed a novel tool designed to expedite and simplify the creation of materials with auxetic properties. This tool, an algorithm, enables precise three-dimensional design of auxetics.

Advanced Tool for Auxetic Design

“This represents a significant leap forward for auxetics,” remarked Edwin Chan, a materials research engineer at NIST and co-author of the study. “We now have the capability to fine-tune the material’s mechanical properties to achieve the desired behavior.”

The behavior of elastic materials is partially governed by Poisson’s ratio, which quantifies how a material changes shape when stretched or compressed in one direction.

Most materials exhibit a positive Poisson’s ratio, meaning that compressing them in one direction causes them to expand in another. Stretching them makes them narrower and thinner. Auxetics, however, possess a negative Poisson’s ratio, doing the exact opposite.

When you apply force to a non-auxetic material, it tends to thin out and expand laterally. In contrast, when you strike an auxetic material, it compresses and narrows, which, under certain conditions, provides superior impact resistance.

For instance, when you strike a water-filled bag, the liquid disperses away from the impact site. If the bag were filled with an auxetic foam, however, the material would densify and stiffen in response to the impact.

auxetic material design algorithm: Potential Applications in Safety and Comfort

This is why auxetics are under consideration for use in buildings and vehicles—they have the potential to enhance protection against explosions and collisions. In footwear, an auxetic gel or rubber foam could provide superior cushioning when the foot strikes the ground.

In textiles, auxetic nylons, fibers, and other synthetics may offer greater comfort than conventional materials. Because they expand when stretched, they more evenly distribute pressure across the body, which could alleviate strain on the back, joints, neck, or shoulders. Research into auxetic materials for bra straps, for instance, found that “auxetic polyester and nylon structures exhibited remarkable pressure distribution capabilities.”

The tool developed by NIST and University of Chicago scientists employs an “inverse design” algorithm, allowing users to specify the desired Poisson’s ratio for their auxetic material. The algorithm then generates an optimized structure for the material.

Another way to describe Poisson’s ratio is that it expresses the relationship between shape and volume as one of these variables changes. The new algorithm allows for precise manipulation of this relationship, creating auxetic materials with behaviors that are not found in nature.

“Our work is a prime example of theoretical, experimental, and computational science converging to achieve something novel,” said NIST materials research engineer Marcos Reyes-Martinez. “With a method to enhance auxetics, we can expect to see them more widely integrated into everyday products.”

The researchers have patented the algorithm along with the underlying methodology and its implementation via 3D printing.

Reference

“An autonomous design algorithm to experimentally realize three-dimensionally isotropic auxetic network structures without compromising density” by Meng Shen, Marcos A. Reyes-Martinez, Louise Ahure Powell, Mark A. Iadicola, Abhishek Sharma, Fabian Byléhn, Nidhi Pashine, Edwin P. Chan, Christopher L. Soles, Heinrich M. Jaeger, and Juan J. de Pablo, May 29, 2024, npj Computational Materials.