A few years ago I stood on an amazingly picturesque hill in Costa Rica overlooking Lake Arenal. I closed my eyes, taking in the warmth of the sun. Suddenly, I felt a sharp pain. I looked down to see a virtual onslaught of red fire ants climbing up my feet and legs, biting all the way.
Today, when I read about the work being done by Binghamton University’s Assistant Professor Rob Wagner, who is investigating the adaptive response of living rafts formed by red ants, and that the ants could actually teach us something and not just inflict pain, I was all ears. Fire ants bind together to create buoyant rafts that allow them to traverse over water—a good skill to have as their habitat floods often. The ants form a condensed, adaptive material where the building blocks (ants) are alive. This behavior has a lesson for us in self-healing materials.
CREDIT: Robert Wagner
Binghamton University Assistant Professor Rob Wagner led research at the University of Colorado Boulder investigating the adaptive response of these living rafts. In their most recent publication in the Proceedings of the National Academy of Sciences, Wagner and his team investigated how fire ant rafts responded to mechanical load when stretched and compared the response to dynamic, self-healing polymers.
Since the rafts are ants clinging onto one another, the bonds holding it together can break and reform. Wagner and his collaborators tried replicating the rafts and discovered that the ants never flowed regardless of the speeds at which the team pulled the ant rafts, they never flowed. The ants seem to reflexively tighten and prolong their holds when they feel force because they want to stay together.
This phenomenon of bonds that grow stronger when force is applied to them is called catch bond behavior and makes sense for survival.
Wagner believes that mimicking these catch bonds in engineered systems could lead to artificial materials with autonomous, localized self-strengthening in regions of higher mechanical stress.
In complex living systems, catch bonds can hold on for longer durations under some range of applied force. Mimicking the catch bonds in engineered systems could lead to artificial materials that exhibit autonomous, localized self-strengthening in regions of higher mechanical stress, enhancing the lifetimes of biomedical implants, adhesives, fiber composites, soft robotics components, and other systems.
You can see videos of the team’s ant testing in action in their paper here.
Maybe someday, I’ll tell you about the army ants that marched in columns on my house in Nuevo Areal.
