Image Courtesy: CU Boulder
Researchers at the University of Colorado Boulder have developed an unusual material that can rapidly switch between being strong and stable or loose and easily separated, a discovery that could pave the way for recyclable construction materials and shape-shifting robotic systems.
The material is made from specially designed particles that become entangled with one another, much like a tightly compressed bundle of office staples. Although the particles remain separate pieces, their interlocking geometry allows them to behave like a solid object under certain conditions. The findings were recently published in the Journal of Applied Physics.
The study was led by researchers in the Paul M. Rady Department of Mechanical Engineering at the University of Colorado Boulder. Professor Francois Barthelat and his team focused on a phenomenon known as entanglement, where particles become intertwined and form strong connections. Similar structures can be found throughout nature, including bird nests and bone tissue, where networks of interwoven materials contribute to overall strength.
To investigate the concept, the team used computer simulations to test how different particle shapes interacted. They discovered that geometry plays a critical role in determining whether particles can lock together. Unlike smooth grains of sand, which cannot easily interconnect, specially shaped particles can form stable networks capable of supporting significant loads.
The most successful design resembled a staple with two protruding legs. During laboratory testing, these staple-like particles produced the highest levels of entanglement while also demonstrating a rare combination of strength and toughness, two properties that are often difficult to achieve simultaneously in conventional materials.
Researchers also found they could control the material’s behavior using vibrations. Gentle vibrations encouraged the particles to interlock more tightly, increasing strength. Stronger vibrations caused the network to break apart, allowing the material to return to a loose collection of individual particles.
The ability to repeatedly assemble and disassemble could make the technology useful in sustainable construction. Future buildings, bridges, and infrastructure could potentially be built using entangled materials that can later be dismantled and reused rather than demolished. The concept may also find applications in swarm robotics, where small robots could join together temporarily to perform tasks before separating again.
The team is now experimenting with even more complex particle shapes inspired by burrs that cling to clothing. Researchers hope these designs will create stronger entanglement effects and unlock new possibilities for adaptable materials.
