Why can water spiders walk on water? Why does the lotus leaf "sludge without staining"? Why won't the butterfly's wings get wet? In fact, these are related to the superhydrophobicity of the surface of the "body" of animals and plants.
Inspired by the above natural phenomena, people gradually grasp the secret of the material's hydrophobicity-it has excellent repulsion to water, water droplets keep a spherical shape on its surface, and it is easy to roll, and the water droplets can also take away the surface of the material Dust to achieve a cleaning effect.
However, the surface structure of superhydrophobic materials prepared by people in the past is very fragile and difficult to achieve wide application. How to coat the surface of superhydrophobic materials with strong "armor" without affecting its hydrophobic performance has become the direction of efforts of researchers in this field.
The reporter learned from the University of Electronic Science and Technology that the "Nature" magazine recently published the latest scientific research results of the team of Professor Deng Xu of the school's basic and cutting-edge research institute in the form of a cover article. This article called "Designing a Strong Superhydrophobic Surface" proposed that The way to "put on" super-hydrophobic surfaces with micro-structured "armor" with excellent mechanical stability can solve the key problem of insufficient mechanical stability of super-hydrophobic surfaces.
Superhydrophobicity vs mechanical stability
Fish and bear paws are difficult to choose
In recent years, due to their unique physical properties, superhydrophobic materials derived from animal and plant bionics have shown great application potential in fields such as surface self-cleaning, biological antifouling, waterproof and anti-icing, fluid drag reduction, and heat and mass transfer. .
It is understood that the superhydrophobicity of superhydrophobic materials can be attributed to the micro/nano-rough structure that can trap air and hold up droplets.
"However, this structure will also lead to super-hydrophobic materials that are more susceptible to wear and breakage." Wang Dehui, the first author of the paper and a Ph.D. Changes occur, changing it from hydrophobic to hydrophilic.
"According to previous scientific research, people think that the mechanical stability and superhydrophobicity of the surface of the material are two characteristics that cannot be achieved at the same time." Wang Dehui said that this is because the micro/nano rough structure reduces the contact area of ​​the material with water. Ways to increase the hydrophobicity, which will also cause the micro/nano structures to withstand higher local pressure, which is more susceptible to wear. This means that in the conventional superhydrophobic materials, the two characteristics of superhydrophobicity and mechanical stability will inevitably lead to a decrease in the performance of the other side when the performance of one side is improved.
Optimized design of microstructure "armor"
New materials win-win in one fell swoop
To achieve double superposition of the mechanical stability and superhydrophobic performance of the same material surface, it is necessary to install "armor" on the surface of superhydrophobic materials with weaker mechanical properties.
"On the one hand, achieving mechanical stability requires geometric design on a larger structural scale; on the other hand, to ensure good superhydrophobicity, structural optimization must be carried out at the nanoscale." Wang Dehui said, according to conventional ideas, it is difficult Compatible with the above two performances at the same scale. Can you try to split it? The corresponding author of the paper, Professor Deng Xu of the Institute of Basic and Frontier Research of the University of Electronic Science and Technology and his team proposed a new experimental idea: that is, the super-hydrophobicity and mechanical stability are separated into two different structural scales through the "decoupling mechanism". After optimizing the design separately, and then combining them together, let the microstructures that provide mechanical stability play the role of "armor" to prevent the superhydrophobic structure from being worn.
"Microstructure is to achieve micron or even more macro-scale levels. This structure is more wear-resistant and durable, and can provide mechanical stability to protect nanomaterials from wear; the protected nanostructures mainly assume super-hydrophobicity." Wang Dehui said, In this way, the microstructure "armor" prepared by optimizing the design can well protect the superhydrophobic nanomaterial from abrasion, thereby constructing an "armored" superhydrophobic surface.
During the experiment, the team obtained microstructural design principles by combining the infiltration theory and mechanical mechanics analysis, and at the same time used photolithography, cold/hot pressing and other fine processing techniques to prepare the armor structure on silicon wafer, ceramic, metal, glass The surface of the universal substrate is combined with super-hydrophobic nanomaterials to construct an "armored" super-hydrophobic surface with excellent mechanical stability.
Used in self-cleaning solar cells
Future uses will be very wide
The reporter learned that at present researchers have applied this new superhydrophobic material surface to solar cell covers.
"Self-cleaning technology can skillfully use rain or mist droplets to eliminate dust and other pollution, can maintain the efficient energy conversion of solar cells for a long time, and save the fresh water resources and labor costs necessary in the traditional cleaning process." Wang Dehui said.
The team found that the new superhydrophobic material also has comprehensive properties such as resistance to chemical corrosion and thermal degradation, resistance to high-speed jet impact and resistance to condensation failure. In addition, the new material also achieves high light transmittance of the glass armored surface, which will also create conditions for application in self-cleaning vehicle glass and architectural glass curtain walls. (Chen Zhenpeng reporter Sheng Li)
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