Saharan silver ants don’t have an easy life, even by ant standards. To avoid predators, they have to look for food during the hottest time of the day – when desert surface temperatures can reach 158 degrees Fahrenheit.
That’s almost too hot to live. The ants perish if their internal temperature goes higher than just 128.48 degrees Fahrenheit. But these little guys have developed an ingenious method for keeping themselves cool: It’s all about the hair, basically.
Researchers discovered that the unique structure and organization of the ants’ hair allow the creatures to control a wide range of the solar spectrum and keep cool. They published their findings in the journal Science.
To the naked human eye, these ants can resemble droplets of mercury as they scamper across the desert sand, said Nanfang Yu, assistant professor of applied physics at Columbia Engineering.
The ants venture out into the midday sun in 10-minute intervals as they forage for dead insects and other creatures.
When it comes to visible and near-infrared light, the silver ant’s hair coating is highly reflective, researchers found. But the hairs don’t just help keep those solar waves away; the hair coating also functions as an anti-reflective in the mid-infrared solar spectrum range, which lets the ants disseminate their own, internal body heat into the cooler air around them.
“We quickly realized these two effects are actually helping each other,” Yu said. “The combination of this tool leads to the optimum cooling effect.”
Those two processes together help reduce an ant’s body temperature by up to 50 degrees Fahrenheit, according to the study.
Researchers only had a few dozen ants for the experiments, and the most challenging aspect of the work was removing the hair from portions of the ants’ bodies; a process requiring “hours of patience,” Yu said.
The hairs themselves have a triangular shape, and instead of standing straight up, they grow straight and then turn at a 90 degree angle, so they are arranged parallel to the ant’s skin. A small air gap between the skin and hair facilitates the cooling technique.
The researchers also created simulations of the effect produced by the hair shape and structure, and members of the engineering team are now interested in how to use these mechanics to create “metasurfaces” that can withstand high temperatures.
“This is very clever engineering on how to deal with high temperatures,” Yu said. “In engineering terms, this is the best you can do in terms of cooling down an object without using any electricity.”
