Natures wonders: fire ant raft bonds (Introduction)

by David Turell , Thursday, May 16, 2024, 00:19 (124 days ago) @ David Turell

Somewhat like polymers:

https://phys.org/news/2024-05-ants-materials.html

"In their most recent publication in the Proceedings of the National Academy of Sciences, Wagner and his co-authors at University of Colorado investigated how fire ant rafts responded to mechanical load when stretched, and they compared the response of these rafts to dynamic, self-healing polymers.

"'Many polymers are held together by dynamic bonds that break, but can reform," Wagner said. "When pulled slowly enough, these bonds have time to restructure the material so that—instead of fracturing—it flows like the slime our kids play with, or soft-serve ice cream. When pulled very fast, though, it breaks more like chalk. Since the rafts are held together by ants clinging onto one another, their bonds can break and reform. So, my colleagues and I thought they'd do the same thing."

"But Wagner and his collaborators discovered that no matter what speed they pulled the ant rafts, their mechanical response was nearly the same, and they never flowed. Wagner speculates that the ants reflexively tighten and prolong their holds when they feel force because they want to stay together. They either turn down or turn off their dynamic behavior.

"This phenomenon of bonds that grow stronger when force is applied to them is called catch bond behavior, and it likely enhances cohesion for the colony, which makes sense for survival.

"As you pull on typical bonds with some amount of force, they're going to let go sooner, and their lifetime goes down—you're weakening the bond by pulling on it. That is what you see in almost any passive system," Wagner said.

"'But in living systems, because of their complexity, you can sometimes have catch bonds that hold on for longer durations under some range of applied force. Some proteins do this mechanistically and automatically, but it's not like the proteins are making a decision. They're just arranged in such a way that when a force is applied, it reveals these binding sites that latch or 'catch.'"

"Wagner believes that mimicking these catch bonds in engineered systems could lead to artificial materials that exhibit autonomous, localized self-strengthening in regions of higher mechanical stress. This could enhance the lifetimes of biomedical implants, adhesives, fiber composites, soft robotics components and many other systems.'

Comment: once again nature teaches us. Amazing fire ants doing it.