Innovative Entangled Materials: A New Frontier in Engineering

Researchers at the University of Colorado Boulder are pioneering a new class of materials known as "entangled materials," inspired by the structural integrity of tangled office staples. This innovative approach leverages geometric interlocking rather than chemical bonds, allowing these materials to transition between a rigid structure and a loose assembly through targeted vibrations. Professor Francois Barthelat, head of the Laboratory for Advanced Materials and Bioinspiration, emphasizes the potential of these materials, stating, “We believe this technology has the potential to go in many directions.”

Interesting Engineering

The core concept of entanglement involves the physical intertwining of particles, akin to natural structures such as bird nests and bones. The researchers discovered that the shape of the particles plays a crucial role in their ability to interlock. For instance, traditional smooth grains of sand do not interlock effectively, while specially designed "two-legged" staple-shaped particles exhibit superior mechanical interlocking capabilities. PhD student Youhan Sohn explains, “If we change the shape of a grain of sand, we can drastically affect its behavior and mechanical properties.”

Interesting Engineering‘Liquid metal’ made of tangled particles could form tough yet flexible structures

The entangled materials exhibit a rare combination of tensile strength and toughness, which conventional materials often lack. The researchers utilized Monte Carlo simulations to identify optimal particle geometries, leading to physical tests that confirmed the effectiveness of the staple-like shapes. The standout feature of these materials is their ability to rapidly assemble and disassemble in response to vibrational patterns. Gentle vibrations can lock particles into a rigid structure, while more intense vibrations can cause them to unravel completely.

‘Liquid metal’ made of tangled particles could form tough yet flexible structuresInteresting Engineering

The implications of this research extend into various fields, including civil engineering and robotics. Barthelat suggests that these materials could enable large structures, such as bridges, to be “unzipped” and recycled rather than demolished, thereby supporting a circular economy. Additionally, the technology could enhance swarm robotics, allowing fleets of small machines to interlock for specific tasks and then disentangle to navigate confined spaces. Barthelat likens this capability to the shape-shifting liquid metal robot T-1000 from *Terminator 2*.

Interesting Engineering

The research team is currently exploring new particle shapes modeled after high-grip plant burrs to achieve even stronger entanglement properties. While challenges remain, particularly in scaling the technology, the potential applications of entangled materials in engineering are vast and promising. The findings of this study were published in the *Journal of Applied Physics*, marking a significant step forward in material science.

Interesting Engineering

• “We’ve been playing around with the idea of building blocks and geometry for many years, but we started looking at interlocking, entangled particles only recently,” — Professor Francois Barthelat, University of Colorado Boulder

Interesting Engineering

• “Our entangled granular material using the staple-like particle demonstrates both high strength and toughness at the same time,” — Saeed Pezeshki, PhD Student

‘Liquid metal’ made of tangled particles could form tough yet flexible structures

• “It’s a strange material because it’s obviously not a liquid. However, it’s also not quite solid. This opens new and intriguing engineering possibilities,” — Professor Francois Barthelat

Interesting Engineering

This innovative research into entangled materials represents a significant advancement in engineering, with the potential to reshape how structures are designed and utilized in the future.

‘Liquid metal’ made of tangled particles could form tough yet flexible structures