Eucalyptus
The eucalyptus is cultivated all over the world and leaves from young trees are rounded and blue-green with a silvery bloom, those from mature trees are longer, pointed, tough and glossy green. The leaves are arranged to be most suited to the climate and productive of peculiar effects of light and shade. Nearly all Eucalyptus is evergreen but some tropical species lose their leaves at the end of the dry season. As in other members of the myrtle family, Eucalyptus leaves are covered with oil glands. The copious oils produced are an important feature of the genus. The leaves on a mature eucalyptus plant are waxy or glossy green.
Self-cleaning properties
Researchers of Murdoch University have discovered that a eucalyptus plant native to south west WA has unique self-cleaning and water-repellent properties which could be used for nanotechnology applications. The tree also known as The Rose of the West for its large spectacular flowers, has silvery leaves covered in a wax and produces nano-sized bumps and pillars. This causes water to form droplets to roll over the surface of the leaves and fall towards the root system of the plant, picking up any dirt along the way. These properties, which are known as super hydrophobic and self-cleaning, are similar to the lotus plant's which has inspired a range of self-cleaning and anti-bacterial technologies currently being developed.
Development
An experiment was carried out by the researchers by coating the leaf with carbon black toner from a laser printer cartridge and then observing how the rolling drops of water were able to completely clean the surface of the leaf. The Eucalyptus' waxes gave the leaves remarkable wetting and self-cleaning properties due to surface features.
The team extracted waxes from the leaves and found that they were capable of self-reassembly. When coated on laboratory glass slides, the wax formed features which mimicked the complex three-dimensional geometry of the nano-sized bumps and pillars found on the original leaf surface, making the slide super hydrophobic. It was fairly easy and inexpensive to extract the wax from the leaves and yet the wax still had these remarkable qualities. The added buoyancy support of the wax meant that it was able to carry a greater load than the uncoated slides.
Application
This discovery has the potential to be applied in a variety of ways, from so-called lab-on-a-chip settings in medical research, to the treatment of ships' hulls to help prevent the build up of harmful microorganisms, plants and animals. In micro fluidic devices used in advanced medical research and disease testing, such coatings could help to maintain the sterility of devices which need to be used over and over again.