Anti Reflective Coatings

Anti Reflective Coatings

Reflection is one major reason why it is difficult to read a phone screen in bright sunlight. Many of today’s smartphones use a sensor to detect bright environmental light and then increase the screen brightness level enough to overcome the strong surface reflection. But there is a limit to how bright the screen can go and the obvious over consumption of energy is notable. 

In order to find a simpler approach to improve screen readability outside, researchers turned to nature. Biomimicry is the design and production of materials, structures, and systems that are modeled on biological entities and processes. Often these designs made with biomimetics is more versatile and efficient than the designs we came up with on our own. 

The surface of moth’s eyes are covered with an unusual natural nanostructured film which eliminates reflections. This allows moths to see well in the dark without giving away their location from light reflecting off of their eyes. The structure is consisted of a hexagonal pattern of bumps, each roughly 200nm high and spaced on 300nm centers. The bumps are smaller than the wavelength of visible light, therefore the light sees the surface as having a continuous refractive index gradient between the air and the medium, which decreases reflection by effectively removing the air-lens interface. Practical anti-reflective films have been made by humans in this way as a form of biomimicry. 

Scientists at the College of Optics and Photonics, University of Central Florida, created a new antireflection coating using inspiration from the structure of moth eyes. These new antireflective films exhibit a surface reflection of just .23 percent, much lower than the standard reflection of 4.4 percent in smartphones. 

Because the nanostructure of moth eyes are so small, it was difficult to fabricate an antireflection film. A high-resolution, high-precision fabrication technique is necessary. The researchers were able to develop a fabrication technique that uses self-assembled nanospheres to form a precise template that can be used to create the moth eye-like structure on a coating. 

By using this technology, we can use this coating on solar panels in order to increase their efficiency. One of the major reasons of wasted energy in photovoltaic products is around 4 percent of light being reflected off of the surface. If this screen was used instead to create solar panels, the wasted light would be around only .23 percent, making the conversion of energy much more effective. 

Another usage could be coating the backup camera, navigation panels, and audio panels in automobiles. If there is a glare on the backup camera, it will be difficult to notice obstacles or people behind the vehicle even if you turn your head. Navigation and audio screens are susceptible to the sunlight’s glare as well, making it hard to identify what the panels say. 

Smart phones as well as any screen such as TVs and computer monitors near a bright light source will benefit greatly from this technology as it will not be necessary to turn off the lights in a room to observe the screens anymore. 

Bibliography

“Figure 2f from: Irimia R, Gottschling M (2016) Taxonomic revision of Rochefortia Sw. (Ehretiaceae, Boraginales). Biodiversity Data Journal 4: e7720. https://Doi.org/10.3897/BDJ.4.e7720.” doi:10.3897/bdj.4.e7720.figure2f.

Katherine Bourzac, Chemical & Engineering News. “Moths Inspire Antireflective Coating that Could Help Devices Capture Light.” Scientific American, 3 Mar. 2015, www.scientificamerican.com/article/moths-inspire-antireflective-coating-that-could-help-devices-capture-light/.

ScienceDaily, ScienceDaily, www.sciencedaily.com/releases/2017/06/170622104033.htm.

“Anti Reflective Coating: usage for solar panels.” Sinovoltaics - Your Solar Supply Network, sinovoltaics.com/learning-center/solar-cells/anti-reflective-coating-for-solar-panels/.

Kim, Jeehwan, et al. “Three-Dimensional a-Si:H Solar Cells on Glass Nanocone Arrays Patterned by Self-Assembled Sn Nanospheres.” ACS Nano, vol. 6, no. 1, 2011, pp. 265–271., doi:10.1021/nn203536x.