Bio-inspired Anti-adhesive Surfaces Stop Bugs in their Tracks

Taking inspiration from slippery plant surfaces, scientists have developed a bio-inspired material that will prevent bugs from crawling and climbing upon. The material could eventually be used to coat surfaces of walls and machines where bugs are unwanted.

The research team from the Plant Biomechanics Group at the University of Freiburg, Germany, studied plant surfaces in order to determine the specific cellular formation and microstructures that are in place to keep bugs from clinging on.

For their experiemets, the researchers used Colorado potato beetles and analysied the bugs as they walked along a variety of plant surfaces as well as man-made resins.

Using a highly sensitive sensor, the researchers were able to measure down to the micrometer the traction forces of the beetles across the various surfaces.

Wavy or strongly curved cells, they learned, can increase the adhesive powers of beetles, whereas microstructures composed of wax crystals or cuticular folds reduce them. Cuticular folds are tiny creases the protective layer on the surface of the leaf. The beetles exhibited the greatest difficulty moving across surfaces with cuticular folds with a height and width of approximately 0.5 micrometers and a spacing of between 0.5 and 1.5 micrometers.

Project director Thomas Speck called the wax cryatals the "perfect" anti-adhesion surface. "The insects slip off of it much easier than off glass," he said.

"The cuticular folds reduce the contact area between the adhesive hairs on the beetles' legs and the plant surface. Unlike on more coarsely structured surfaces, the beetle can't dig its feet firmly into the cuticular folds," the researchers said in a statement. "Thus, the microstructure of the surface has a stronger effect on the adhesion of the beetle than the cell form."

Speck and his colleagues' research is published in the current edition of the journal Acta Biomaterialia.