How ants keep clean

 

Zoologists from the University of Cambridge, UK, have used SEM to discover how ants use different types of hair to clear dirt away from antennae.

 

Stunning images reveal how three clusters of hairs perform a different function in the cleaning process, a discovery that could help researchers identify contaminants that insects cannot easily clean, providing new routes towards pest control.

 

Contamination by micro-organisms, fungal spores and parasitoids can be life-threatening to insects, which have developed a variety of mechanisms to clean of body parts.

 

As Alexander Hackmann from the Department of Zoology, Cambridge University highlights: “Insects have developed ingenious ways of cleaning very small, sensitive structures, so finding out exactly how they work could have fascinating applications for nanotechnology, where contamination of small things, especially electronic devices, is a big problem."

 

"Different insects have all kinds of different cleaning devices, but no-one has really looked at their mechanical function in detail before,” he adds.

 

Camponotus rufifemur ants possess a specialised cleaning structure on their front legs that is actively used to groom their antennae.

 

A notch and spur covered in different types of hairs form a claw-like cleaning device.

 

During a cleaning movement, the antenna is pulled through the device which clears away dirt particles using ‘bristles’, a ‘comb’ and a ‘brush’.

 

 

To investigate how the different hairs work, Hackmann painstakingly constructed an experimental mechanism to mimic the ant’s movements and pull antennae through the cleaning structure.

 

He went on to contaminate the ants' antennae with fluorescent particles, and during his studies, discovered the three clusters of hairs perform a different function in the cleaning process.

 

Video footage and SEM images reveal that the dirty antenna surface first comes into contact with the ‘bristles’ (shown in the SEM image in red) which scratch away the largest particles.

 

 

It is then drawn past the ‘comb’ (shown in the image in blue) which removes smaller particles that get trapped between the comb hairs.

 

Finally, it is drawn through the ‘brush’ (shown in the image in green) which removes the smallest particles.

 

“While the ‘bristles’ and the ‘comb’ scrape off larger particles mechanically, the ‘brush’ seems to attract smaller dirt particles from the antenna by adhesion,” explains Hackmann. 

 

According to the researcher, the ‘bristles’ and ‘comb’ are rounded and fairly rigid, while the ‘brush’ hairs are flat, bendy and covered in ridges, increasing the surface area for contact with the dirt particles, which stick to the hairs.

 

Researchers do not yet know what makes the ‘brush’ hairs sticky – whether it is due to electrostatic forces, sticky secretions, or a combination of factors.

 

“The arrangement of ‘bristles’, ‘combs’ and ‘brush’ lets the cleaning structure work as a particle filter that can clean different sized dirt particles with a single cleaning stroke,” says Hackmann.

 

“Modern nanofabrication techniques face similar problems with surface contamination, and as a result the fabrication of micron-scale devices requires very expensive cleanroom technology," he adds. "We hope that understanding the biological system will lead to building bioinspired devices for cleaning on micro and nano scales."

 

Research is published in Royal Society Open Science