Scientists are currently highly interested in surfaces that can kill bacteria, and dragonfly wings may be able to help.
Research into bacteria-killing surfaces has included infusing a slippery surface with molecules that disrupt bacterial communication and using deadly silver nanoparticle coatings.
The most brutal example uses black silicon to rip bacteria apart on a ‘bed of nails’ consisting of nanopillars. This is part of research into nano-textured surfaces (NTS), which nature has its own examples of – including dragonfly wings.
The wings kill bacteria with a structure very similar to that created by black silicon.
Why are dragonfly wings so effective?
Until now, experts believed that the so-called bed of nails punctures the cell wall in order to inflict damage. But a team of Australian and Nigerian researchers has used microscopy techniques to come up with a new theory.
The researchers noticed that in dragonfly wings the nanopillars were not of equal height, which does not apply in bed of nails tests.
In fact, they noted, with dragonfly wings the bacterial membrane has no direct contact with the nanopillars. Instead, the nanopillars attach to extracellular polymeric substances (EPSs) – structural molecules secreted by the bacteria (E. coli in this study). They also attach to “finger-like” extensions.
Adhesive forces then deform the bacterial membrane, even though they may not actually be enough to cause rupture. Bacteria are now in trap a which they could probably survive for a time if they remained still. However, once they move, the force on the EPSs causes the membrane to be torn apart and cellular content of the bacteria to leak out like air from a balloon.
Finally, the nanopillars penetrate the dead cells.
Although a change in accepted theory may be on the cards, further tests are required. Tests on bacteria with only one membrane (E.coli has two) as well as on bacteria with fewer EPSs are needed. New experiments that amend the synthetic bed of nails to give pillars of different heights are also desirable.
One thing is for certain, though – as well as being beautiful, dragonfly wings are also clean.