Research has often taken inspiration from nature to make its most promising steps. For example, an international research team working with graphene recently tried to obtain an artificial nanomaterial reproducing one of the most surprising and useful features of lotus leaves.
Thanks to their particular structure, in fact, lotus leaves are strongly hydrophobic, and let the muddy water of the rivers and lakes in their habitat slide away, thus allowing the plant to remain constantly dry, protected, and clean.
This peculiarity, by which the lotus flower is a symbol for pureness in most eastern countries, is also highly appreciated in a variety of industries, from flexible and transparent next generation electronics to nanomedicine.
However the waterproof property of lotus – and this is the issue that science set out to address – cannot be controlled.
The challenge for the scientists at the Trento University, the Duke University, and the MIT -Massachusetts Institute of Technology was therefore to create an artificial leaf similar to the natural one, but whose features could be controlled and modified artificially. The goal was to generate a smart, cross-functional surface fit for a variety of applications.
The key to success was concealed in a sheet of graphene, a material whose special structure allows to reproduce the waterproof features of the lotus leaf in a controlled manner, or “at need”. According to its structure, in fact, it can strongly attract or repel water.
In order to achieve this, the scientists performed nanomechanics calculations and atomistic simulations and applied a layer of “wrinkled” graphene to an extremely supple polymeric surface. The substrate was then submitted to mechanical stress, which caused graphene to change its shape from corrugated to smooth. This “relaxing” effect allowed the innovative product to change its condition from super-hydrophobic to hydrophilic.
“The artificial leaf that we created is also conductive and can still be over-warped without breaking,” explains Nicola Pugno, regular professor of Building Science at the Department of civil, environmental, and mechanical engineering of the Trento University and co-ordinator of the study. “This feature is crucial, for example, to develop flexible next-generation electronic systems. Moreover, the artificial leaf is transparent, and such transparency is also controllable.
This smart multi-functional behaviour is reversible thanks to the robustness of the system, which can therefore work for lots and lots of cycles. The macroscopic size of the system allows multiple applications. One example of the potentials of this finding is the creation of an artificial muscle.”
The study was published in the review Nature Materials.
Published on Friday, February 1, 2013