Recently, Dr. Huang Gan from the Karlsruhe Institute of Technology in Germany and his team have created a type of metamaterial made from polymers.
The surface structure is composed of countless tiny pyramids, the width of which is about one-tenth of the diameter of a human hair.
This micro-pyramid structure has the property of diffusing sunlight, and through multiple reflections, it can minimize reflection losses.
During the testing process, the team was pleasantly surprised to find that, in addition to the expected radiation cooling, self-cleaning, and scattering functions, this metamaterial roof can also introduce morning and evening light into the interior through the micro-pyramid prism effect.
Through light simulation, they further explained this phenomenon and confirmed the superior performance of the material under different lighting conditions.In addition, the emissivity of the micro-pyramid structure is close to the ideal mid-infrared blackbody emissivity, thereby enabling efficient passive radiative cooling.
Utilizing the similarity between the micro-pyramid and the microstructure on lotus leaves, this metamaterial also possesses excellent superhydrophobic properties, which contribute to self-cleaning functions.
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More importantly, this metamaterial is made from environmentally friendly and safe polymer materials available on the market, and has the potential for large-scale manufacturing.
Won first place in the Best Scientific Image Competition of the German Helmholtz Association
It is also reported that while conducting research in the laboratory, they also hope to make the public aware of this technology.For this purpose, they participated in the Best Scientific Image Competition held by the German Helmholtz Association. The goal of the competition is to introduce scientific research results to the public through images and stories.
As previously mentioned, each square centimeter of this metamaterial surface contains one million tiny pyramids, each of which is only one-tenth the size of a hair strand.
One of the main purposes of these tiny pyramids is to increase the emissivity, thereby better collecting the cold energy in the universe.
To attract public interest, they draw an analogy between these tiny pyramids and the huge pyramids of Egypt.
In mythology, the Egyptian pyramids are believed to be used to absorb cosmic energy, and their tiny pyramids are also for collecting cosmic energy.In order to help the public better understand and accept their research, they artistically processed the micro images, enhancing their visual impact and appeal through the use of color and composition.
Ultimately, their scientific images won first place in the Public Choice Award with the theme "Small-Pyramids Harvest Big-Universe Energy."
At the same time, not only did this image win the favor of the public, but it was also exhibited in a tour at several universities and research institutes in Germany.
In terms of application prospects:
Firstly, it can be used in green building construction.The material presented this time not only provides soft natural light but also protects indoor privacy and utilizes cosmic cold energy for cooling.
By reducing energy consumption and emissions, the research team hopes to provide a more comfortable indoor living and working environment for people.
Secondly, it can be used for solar photovoltaic panels.
Due to the significant light transmission effect of this material (the transmission rate is significantly higher than that of glass) and the self-cleaning effect similar to lotus leaves, it can also be used for the power generation and self-cleaning functions of solar photovoltaic panels.
In this way, not only can the efficiency of the photovoltaic panels be improved, but the impact of the reflected glare from the solar panels on the surrounding light environment can also be reduced.Thirdly, it can be used for automotive glass.
Through this, driving comfort and safety can be enhanced, reducing the harm of glare and ultraviolet rays to the occupants inside the vehicle, while also providing better privacy protection and self-cleaning effects.
Fourthly, it can be used for smart windows.
In smart buildings and homes, this material can be used for smart windows to automatically adjust light, temperature, and privacy protection.
Combined with sensor technology and intelligent control systems, it can further improve the energy-saving effects of buildings and the comfort of living.Its fifth, it can be used for agricultural greenhouses.
That is, as the covering material for the greenhouse, in order to effectively control the temperature and lighting inside the greenhouse, improve the efficiency of crop growth, and reduce maintenance costs.
Traditional transparent building materials gradually cannot meet modern requirements
Undoubtedly, human beings almost cannot do without buildings every day. Buildings are not only the main places for living and working, but also an important source of energy consumption.
Therefore, it is particularly important to build buildings that have both energy-saving effects and indoor environmental comfort.Transparent roofing and curtain wall materials widely used in modern architecture allow people to enjoy natural light while reducing electricity consumption.
Despite the obvious advantages of transparent roofs and walls, traditional glass materials also have some inherent limitations.
For example, glare issues are generally caused by direct transmission or reflection of sunlight, which can lead to discomfort, eye fatigue, and a decline in vision, severely affecting work efficiency and health, especially for people working in strong light environments.
In addition, the transparency of traditional glass brings privacy issues, which are particularly prominent in sensitive places such as hospitals.
In summer, the interior of buildings is prone to accumulate excessive heat, and an effective heat control mechanism is needed to ensure the comfort of the indoor environment, especially in hot and dry areas.Compared to conventional buildings, buildings with transparent roofs and walls consume more electricity for air conditioning systems.
Clean energy, especially solar energy, can be converted into electrical and thermal energy, and can also be directly used for natural lighting in buildings.
Modern energy-saving buildings place great emphasis on the full utilization of natural light, while also having high requirements for the comfort and privacy of the indoor thermal and light environment.
Therefore, building materials need to have high light transmittance, soft light adjustment, and indoor temperature control functions, while also having good stability and self-cleaning capabilities.
Traditional transparent building materials find it difficult to meet these requirements simultaneously, so the research team decided to develop this multifunctional new type of building material."Hope one day I can use it too."
After determining the direction of the topic, the team first analyzed the problems faced by transparent roofs and walls in modern architecture, especially the overheating phenomenon caused by the "greenhouse effect."
Based on this, they established a technical route for radiative cooling using cosmic cold energy.
In recent years, radiative cooling technology has received widespread attention and development, which provides a reference for this research.After a period of research, they decided to utilize microphotonic structures because it not only enhances the material's radiative cooling capabilities towards outer space but also, through scattering effects, makes the light that passes through more gentle.
Furthermore, to achieve superhydrophobic self-cleaning functionality, they drew inspiration from the microstructure design of lotus leaves.
Having determined the general microphotonic structure, the research team collaborated with the micro-nano fabrication laboratory at the same university to prepare samples of micro-pyramids with various structural parameters.
They also combined numerical models to optimize the samples, aiming to achieve the best radiative cooling effect while considering self-cleaning, scattering, and transmittance performance.
After several optimizations, they successfully prepared materials with excellent comprehensive performance.Recently, the relevant paper was published in Nature Communications[1] with the title "Radiative cooling and indoor light management enabled by a transparent and self-cleaning polymer-based metamaterial."
Huang Gan is the first author and co-corresponding author, and Professor Bryce S. Richards from the Karlsruhe Institute of Technology in Germany serves as the co-corresponding author.
After the announcement of this achievement, a German colleague from the same school, Martin, whom Huang Gan did not know before, sent a message: "I feel very honored to work at the Karlsruhe Institute of Technology with people like you! I hope to use this at home one day."
Huang Gan said, "His encouragement makes me feel very warm and inspired. I am very proud that the research I have done is recognized and has an impact."
The exploration of large-scale production of related products will be carried out.Next, the research team will focus on how to achieve large-scale manufacturing of materials and enhance the outdoor stability of materials.
Recently, they have developed a large-scale manufacturing process based on splicing molds, which provides a feasible technical path for mass production of this metamaterial.
Next, they plan to cooperate with the Energy Lab 2.0 of the Karlsruhe Institute of Technology (the largest renewable energy facility in Europe) for pilot applications.
They will use this green building material in the experimental house of Energy Lab 2.0 to test its energy-saving effect and indoor light control effect on the spot.
In detail, they will carry out follow-up work in the following aspects:Firstly, optimization of large-scale manufacturing processes.
The team will continue to optimize the manufacturing process based on splicing molds, ensuring that the material maintains high quality and consistency during large-scale production.
At the same time, they will explore how to further reduce manufacturing costs to make this material more commercially viable.
Secondly, conduct outdoor stability testing.
To ensure the material's long-term stability and performance under various climatic conditions, they will carry out extensive outdoor testing.For example, assessing the weather resistance, self-cleaning effects, and radiative cooling capabilities of materials under different environmental conditions to ensure their reliability in practical applications.
Thirdly, field application and monitoring.
In the experimental house of Energy Lab 2.0, they will install this new type of material and conduct long-term monitoring on it.
The research team will evaluate its performance in energy saving, light control, and comfort by collecting and analyzing data, further verifying and optimizing the actual effects of the material.
Fourthly, industrialization promotion.After ensuring the maturity of the technology, they plan to leverage the resources and platform of the Karlsruhe Institute of Technology to promote the industrialization of the material.
They will seek partners, explore market demand, and formulate commercialization strategies, striving to promote this green building material to more practical applications.
Fifth, further research and innovation.
On the basis of existing research, they will also continue to explore other potential applications, such as in photovoltaic panels and agricultural greenhouses.
Strive to develop more functional and widely applicable new materials to promote the development of green technology.It is also reported that Huang Gan graduated from Huazhong University of Science and Technology for his undergraduate degree and from Tsinghua University for his doctorate. Subsequently, he served as a postdoctoral researcher and research assistant at the University of Oxford and Imperial College London in the UK, respectively.
In 2021, he joined the Karlsruhe Institute of Technology in Germany, where he has been working ever since, and was promoted to the head of a research group in 2022.
In 2023, Huang Gan was selected as one of the "35 Innovators Under 35" in the European region by MIT Technology Review, and he was also the only person selected from Germany that year [2].
Subsequently, he hopes to continue to promote the development of green building materials with his team, contributing to a more energy-efficient and environmentally friendly environment.
