Listen to Tsinghua engineers to talk about "Chinese version of flood control screens"

In order to cope with smog pollution, China has also developed the "Chinese version of flood control screens." This is the research and development result led by Wang Yulan, a senior engineer of the Institute of Nuclear and New Energy Technology of Tsinghua University. A few days ago, the Global Times reporter interviewed Wang Yulan.

Global Times: Can you introduce the principle of the anti-fog window screen developed by your team?

Wang Yulan: The most critical material for this kind of window screening is a film called “nuclear pore film”, which is visually a large number of micron-sized micropores on a thin plastic film. These micropores have a high density of distribution, one square centimeter, which is the size of a fingernail, and there are hundreds of thousands of micropores. Moreover, these micropores are straight through holes that penetrate the membrane material.

Some special chemical properties of the pore walls result in static electricity on the walls of the pores and the surface of the membrane. We know that PM2.5 is a general term for contaminant particles with aerodynamic equivalent diameter ≤ 2.5 microns. These particles are suspended in the air and, when they pass through the membrane material, are adsorbed on the pore walls under the action of static electricity.

Global Times: What is the effect of anti-smog?

Wang Yulan: The effect is related to the specific parameters of the film. For example, under certain parameters, 100% anti-fog can be achieved. When changing to another parameter, the anti-fog effect is 98%. These parameters are mainly micropore pore size and the chemical properties of the material, and can be artificially controlled. For commercial applications, the pore size of the micropores can be controlled from 10 nanometers to tens of micrometers.

Global Times: When it comes to "nuclear pore membranes", ordinary people always associate with nuclear radiation. What is the safety, breathability and durability of this membrane?

Wang Yulan: There is no problem with safety. The nuclear pore membrane and nuclear radiation are completely two concepts. The nuclear pore membrane uses an accelerator to accelerate the nucleus to a high energy, and then bombards the membrane. The nucleus used is not a radionuclide, and does not generate radioactive residues after penetrating the membrane. Strictly speaking, we have monitored and evaluated the radiation of the membrane and concluded that it is safe. This membrane is also an auxiliary material for three types of medical devices and is absolutely safe through biotoxicity monitoring.

The pore size we use is generally a few microns, and the gas molecule diameter is usually a few tenths of a nanometer, much smaller than the pore size, so there is no problem with gas permeability.

The chemical stability of this film is very good. Under ideal conditions, there is no problem for 10 years, but after all, it is applied to the window in daily use, so we added a gauze outside to improve durability.

Global Times: Is this anti-fog window screen mass-produced? What is the approximate cost?

Wang Yulan: There are already enterprise applications, but the mass production of screens also needs to solve some commercial problems with the cooperative enterprises. In the laboratory, the aperture, pass accuracy of a film control was particularly good, no problem, but to keep the aperture, high-quality precision pass in millions of square meters of production, it is necessary to solve many technical problems. Regarding the cost, we must also consider the output, scale, post-composite, and reinforcement.

Global Times: What are the breakthroughs in this project?

Wang Yulan: I have been engaged in nuclear pore membrane technology for many years, but it is accidental to use this technology for anti-fog. Once I saw a joke on the Internet, I realized that smog is really a problem that our people can't avoid. I think at the technical level, we should further optimize the process, reduce the cost, solve the engineering problems, and promote the application as soon as possible to benefit the people.

Global Times: A German company has also launched anti-fog window screens. I wonder if you have any concerns?

Wang Yulan: Some friends got samples of German products and gave us some data. In terms of the efficiency of PM2.5, our technology is far superior to this product in Germany. As for the breathable light transmission, because I did not see the real thing, it is not easy to evaluate. I think that different technologies solve problems at different levels, and each has its own advantages and disadvantages.