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Researchers from Japan have devised a strategy to produce large area moth-eye inspired transparent films that greatly reduce reflectance and improve transmittance. These films could be used to better the visibility of screens and enhance the performance of solar panels.
The optical properties of this film were remarkable; its reflectance toward light in the visible range was only 0.4%, ten times lower than that of a similar film without the moth-eye nanostructure. What's more, the transmittance of light through the material was also increased, meaning that no trade-off in optical properties occurred as a result of using the film to reduce reflected light.
Novel Strategy to Overcome Scalability and Manufacturing Cost Barriers
However, despite the recent progress in nanoscience that allows the adoption of this idea for various practical applications, there are still barriers to overcome in terms of scalability and cost of manufacturing. To tackle these problems, scientists from Tokyo University of Science and Geomatec Co., Ltd., Japan, have been working on a novel strategy to produce moth-eye nanostructures and transparent films. In their latest study, published in Micro and Nano Engineering, they present a promising method to fabricate moth-eye molds and films at large scales.
Though this research team had previously succeeded in creating moth-eye molds made of glassy carbon etched with an oxygen ion beam, this approach was not scalable. "
Producing glassy carbon substrates requires the use of powder metallurgy technology, which is difficult to use to produce molds with a large area," explains professor Jun Taniguchi from Tokyo University of Science, "To overcome this limitation, we tried using only a thin layer of glassy carbon deposited on top a large regular glass substrate."
Using ICP System to Obtain High-quality Nanostructured Mold
Moreover, to make this new strategy feasible, the team opted this time to use an inductively coupled plasma (ICP) system as opposed to the previously used electron-cyclotron resonance ion source. While both devices can etch glassy carbon using a concentrated beam of oxygen ions, ICP technology produces a wider ion beam irradiation range, which is more suitable for working on large-area structures.
After testing with different ICP parameters, the researchers determined that a two-step ICP etching process was best to obtain a high-quality nanostructured mold. Then, they used this mold to produce a transparent film with a moth-eye nanostructure using a UV-curable resin.
Mr Hiroyuki Sugawara, chief technical officer at Geomatec, highlights the many possible applications of such anti-reflective films if it were possible to produce them at the meter scale, "
We could use these films to improve visibility in flat panel displays, digital signs, and the transparent acrylic plates used everywhere since the start of the COVID-19 pandemic. Moreover, anti-reflective coating could also be an efficient way to improve the performance of solar panels."
Source: Tokyo University of Science