Australasian Science: Australia's authority on science since 1938

Raspberries from Roses

By Stephen Luntz

The capacity of rose petals to shape water into droplets that resist the pull of gravity has inspired artists and poets for generations. Now University of Sydney chemists have creating imitations with potential applications so diverse they are just starting to grasp the possibilities.

Dr Andrew Telford says that under an electron microscope it is possible to see that rose petals have what are known as “raspberry particles” shaped like minute versions of the fruit. These, he says, “can trap tiny water droplets and prevent them from rolling off surfaces, even when that surface is turned upside down.

“No one seems to know why roses do this. We only know how.” Telford says that the spherical shape of the droplets is “a sign the flower is highly water-repellent”.

Telford, Dr Chiara Neto and A/Prof Brian Hawkett replicated the raspberry-shaped particles, and the surfaces they created had a similar capacity to hold onto water drops. “Raspberry particle films can be described as sticky tape for water droplets,” says Telford, who has published the results in Chemistry of Materials.

Telford’s team learned that other researchers are seeking a surface like this in order to control condensation in places such as airline cabins, where it is crucial to prevent the water that forms on the walls from getting into the electronics.

Another application is as a way to hold onto blood droplets for medical testing. “We are moving away from needing sterilised containers to hold minute amounts of a sample, instead going towards doing tests on free-standing droplets that are very accessible with optical probes.”

Another potential application involves immobilising water droplets so that substances in solution can crystallise out in the desired location.

“Our team’s discovery is the first that allows for the preparation of raspberry particles on an industrial scale, and we are now in a position where we can prepare large quantities of these particles without the need to build special plants or equipment,” Telford says.

Indeed, he says the particles disperse in water and could be applied to surfaces like paint, a feature that has drawn collaboration with Dr Chris Such of the Dulux Group. The same physical design, but using a different chemical structure, could produce surfaces that do the opposite, Telford says, forcing water to spread quickly to create quick-dry walls or improve the collection of water from roofs.