Victoria Fernández explains one of the greatest enigmas of biological surfaces

It is about explaining in a reliable and proven way the way in which the drops adhere to the rose petals without falling, maintaining their spherical volume, even if the flower or the petals are upside down.

Victoria Fernández, a researcher at the Higher Technical School of Forestry, Forestry and Natural Environment Engineers of the Polytechnic University of Madrid, participates in a study that would explain the fact that dew drops stick to rose petals. A scientific discovery that can open a new era in the construction of materials, in the absorption of liquids by plants and, above all, in the relationship between surfaces and water in its different variables.

Scientific researchers and other science experts have always tried to discover and respond to this attractive and curious phenomenon of nature. It is about explaining in a reliable and verified way the way in which the dew drops adhere to the rose petals without falling, maintaining their spherical volume, even if the flower or the petals are upside down.

rose petal effect

The phenomenon is known as the "rose petal effect" and it is a very hydrophobic surface, which keeps the water droplets almost spherical, although curiously they do not move or slide, but remain attached, which is a great unknown for the science.

In a first phase, a rose variety was selected whose petals kept water droplets adhered in a similar way on their upper (beam) and lower (underside) faces. It was observed that both the texture and the roughness of both surfaces of the petal (both the upper and the lower) are very different. However, they are similarly wetted by drops of water. So surface roughness alone doesn't explain everything.

The researcher Victoria Fernández is one of the academics who will participate in the course: "International expert in irrigation and nutrition in blueberries" taught by the University of Almería in conjunction with Blueberries Consulting, starting on October 17.

AFM

Finally, atomic force microscopy (AFM) analysis provided the answer, by allowing the surface of the petal to be analyzed at a very fine scale, nanometers. The AFM, in addition to perceiving roughness, is capable of capturing the chemical composition of the surface. Thus, it was discovered that the surface of the petals at this scale has fractal roughness, in a range between 5 nm (nanometers) and 20 µm (micrometers).

At this nanometric scale, it was found that the surface of the petal has an irregular tessellation (pattern of figures) that completely covers the surface, although the most striking thing is that this tessera is formed by alternating hydrophilic and hydrophobic nanozones, which solves the mystery. why the rose petal is hydrophobic but adherent to water at the same time.

innovative applications

It should be emphasized that, at the level of plant surfaces, these hydrophilic zones are of great interest, since they can play a fundamental role in the absorption of water and solutes deposited on the leaves, such as aerosols or foliar sprays of agrochemical products, and can also be vulnerable points for the attack of pests and diseases.

By revealing the secret of the "rose petal effect", its great surface roughness and chemical heterogeneity, by having alternating hydrophilic and hydrophobic zones, it will allow materials science and biomimetics (which is the science that studies to imitate them), develop new highly useful surfaces and innovative applications in plants.

  • Made with text by Victoria Fernández published in The Conversation

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