A new material, inspired by the frustratingly powerful strength of a tangled ball of staples, could represent the future of flexible, adaptable design.
Published in the Journal of Applied Physics, material scientists and engineers from the University of Colorado Boulder’s Paul M. Rady Department of Mechanical Engineering revealed an interlocking particle design that can be shaped into rigid structures, and then return to a pile of loose pieces with only a targeted movement or vibration.
The particles, the team says, could potentially be used as a building material with high strength and flexibility, capable of reshaping into new forms on command.
Staple Ball Strength
The difficulty of separating tangled metal, such as a cluster of standard office staples, intrigued the researchers enough to investigate how interlocking particles could be used in recyclable construction. Such techniques are found in nature, as birds weave together found objects to create strong structures to protect their young.
On the level of particles, interlocking such elements is called “entanglement,” and is a relatively new focus for material scientists.
“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,” said Professor Francois Barthelat, the leader of the Laboratory for Advanced Materials & Bioinspiration.
“We are excited about the combination of properties we can get out of these systems, and we believe this technology has the potential to go in many directions,” Barthelat said.
Manufacturing Entanglement
While entanglement occurs naturally, as in the combination of soft protein and hard minerals that interlock to form bones, producing it artificially requires a careful understanding of how these interactions work. According to the team, particle shape is the most foundational element to natural entanglement.
“Let’s take sand as an example,” says PhD student Youhan Sohn. “Sand is smooth and convex-shaped, meaning it cannot interlock from grain to grain.”
“However, we found that if we change the shape of a grain of sand, we can drastically affect its behavior and mechanical properties, including the particle’s ability to link with other particles,” Sohn adds.
With shape decided as the researcher’s primary focus, they began running computer models, called Monte Carlo simulations, to observe how various potential shapes would interact, aiming to identify the optimal entanglement geometry. The shape their research settled on was remarkably similar to that of a staple: a particle with two legs.
Laboratory Material Experiments
After achieving success in the digital realm, the researchers fabricated the shape in the real world to test its behavior under practical conditions. During these tests, the team discovered that their optimized shape contained even more beneficial qualities than they had initially understood.
Conventional materials typically experience a trade-off between toughness and tensile strength. Typically, materials that are extremely tough and can absorb large amounts of energy are also quite brittle, lacking the ability to stretch or bend. However, this staple-like particle design exhibits an unusually high amount of both properties simultaneously.
“Our entangled granular material using the staple-like particle demonstrates both high strength and toughness at the same time,” said PhD student Saeed Pezeshki.
Additionally, they discovered that applying different vibrational patterns would change the particles’ degree of entanglement, allowing the team to assemble and disassemble a shape instantly. Applying a light vibration caused the pieces to interlock, whereas a heavy vibration untangled them as a pile of loose particles.
Material Applications
“No binder is required, so particles can be rapidly assembled in an infinite number of shapes, which can be reconfigured with appropriate mechanical stimuli, making them attractive for lightweight and reversible materials and structures and aggregate architectures,” the authors recently wrote.
“The fundamental understanding of entanglement gained in this project is also relevant to other physical systems, including biological structures, ‘living’ entangled matter, robotic materials, as well as colloidal assemblies,” the authors add.
“It’s a strange material because it’s obviously not a liquid. However, it’s also not quite solid,” Barthelat said. “This opens new and intriguing engineering possibilities.”
“Handling a bundle of these entangled particles feels very remote and exotic,” he added.
The paper, “Combined Effects of Particle Geometry and Applied Vibrations on the Mechanics and Strength of Entangled Materials,” appeared in the Journal of Applied Physics on April 14, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.