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New surface coatings give insects the slip


September 27, 2013

A Colorado potato beetle tries to find purchase on one of the slippery surfaces

A Colorado potato beetle tries to find purchase on one of the slippery surfaces

Not having air conditioning in my house, here's something I didn't know: the inner surfaces of air conditioner ventilation pipes are often covered in cockroaches. Nice. In order to keep the roaches out of those pipes – along with keeping other insects out of other places – scientists from Germany's University of Freiburg have developed new bio-inspired surface coatings that even sticky-footed bugs can't cling to.

The Freiburg researchers started by observing Colorado potato beetles as they walked across a number of plant surfaces, along with replicas of those surfaces made from synthetic resins. A sensor was used to measure how much traction the beetles were able to maintain.

It was found that while surfaces consisting of curved or wavy arrangements of cells provided the most traction, the least traction was offered by surfaces that incorporated "cuticular folds." As the name suggests, these are tiny folds that occur in the protective outer cuticle of a leaf.

On surfaces with cuticular folds that are sized just right – having a height and width of about 0.5 micrometers and a spacing between 0.5 and 1.5 micrometers – the beetles have even less grip than they do on glass. This is because of the reduced contact area between the surface itself and the adhesive hairs on the insects' legs.

As an added bonus, such surfaces are also very water-repellent.

The scientists are now working on bringing man-made versions of the insect-unfriendly surfaces into commercial production, with hopes of using them not only inside of air conditioner pipes, but also on things like window frames. They also want to establish a means of adapting the sizing of the folds, in order to customize the surfaces for keeping out different types of insects.

A paper on the research was recently published in the journal Acta Biomaterialia.

Source: University of Freiburg

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

"the inner surfaces of air conditioner ventilation pipes are often covered in cockroaches." Not in my experience, and I am in Florida USA with plenty of cockroaches and air conditioning. Who is the source of this little "factoid".

Dave B13

Good God! Where do you have to live to "often" have roaches in air conditioning ducts? I've had AC in Southern California, Ohio, and South Texas over the past 60 years and have never heard of that.


@ Dave B13 I know, I have never seen ducts with cockroaches (FL)this is a factoid from the duct cleaning people that tear your ducts up with their spinning brush.

Jay Finke

Cockroaches don't like airflow, do they?

Oun Kwon
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