On a scorching summer day, we often instinctively reach for light-colored clothing as they are believed to keep us cooler by reflecting sunlight instead of absorbing it. However, researchers have recently made a breakthrough in developing cooling films that are capable of maintaining vivid colors without absorbing any light. Inspired by the nanostructures found in butterfly wings, these innovative films have the potential to revolutionize energy sustainability and reduce the energy consumption needed for cooling.
The researchers, led by Wanlin Wang from Shenzhen University in China, drew inspiration from the nanostructures found in Morpho butterfly wings. These wings produce a brilliant, highly-saturated blue color without absorbing light. By mimicking this natural phenomenon, the researchers were able to develop nanofilms that preserve vibrant colors while effectively lowering temperatures.
Passive Cooling Method
The key to these cooling nanofilms lies in their layered structure. A disordered material, resembling rough frosted glass, is placed beneath a multilayer material composed of titanium dioxide and aluminum dioxide. This entire structure is then positioned over a reflective silver layer which prevents the absorption of solar radiation and associated heating. The resulting color of the film is determined by how light is reflected within its multilayered structure, enabling the creation of various colors with high saturation and brightness.
The researchers conducted extensive testing on the cooling films by placing them outdoors on different surfaces, including roofs, cars, cloth, and cell phones. Using thermocouple sensors and infrared cameras, they measured the temperatures of these surfaces compared to the films. The results were astounding – the films were more than 15°C cooler than the surfaces they were applied to during winter and around 35°C cooler during summer.
Energy Savings and Applications
The potential energy savings from implementing these cooling films are significant. In fact, the researchers estimated that the annual energy savings could reach approximately 1,377 MJ/m2 per year. This makes the films suitable for a wide range of applications, from building exteriors to vehicles and even textiles. By incorporating these films into clothing, individuals would be able to wear garments of any color while remaining comfortable in hot temperatures.
While the current nanofilms utilize a silver layer, the researchers believe that replacing it with a more cost-effective aluminum film would make the technology more accessible and scalable for mass production. Techniques such as electron beam evaporation and magnetron sputtering could be employed for fabrication. Additionally, the researchers plan to optimize the mechanical and chemical robustness of the films now that their cooling and color performance has been successfully demonstrated.
The development of nanostructured cooling films inspired by butterfly wings opens up new possibilities for energy sustainability and carbon neutrality. By harnessing the power of reflection and combining it with vibrant colors, these films have the potential to revolutionize the way we cool our buildings, vehicles, and even ourselves. As further advancements are made, we can look forward to a future where energy-intensive cooling becomes a thing of the past, replaced by environmentally friendly and aesthetically pleasing solutions.
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