Anti-Reflective Film Inspired by Moth Eyes

Innovation: Academia

University of Central Florida

2017

Image: Lucie Hůrková / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Modify Light/Color

Color in living systems comes from pigments and the interaction of light with surfaces. Color serves many purposes for living systems, such as attracting prey or mates, providing warnings, or protecting through camouflage. To create the effects needed for each purpose, living systems must control the expression or visibility of pigments and the interactions (such as reflectance and refraction) of light. To do so, they have strategies that modify color or light to increase or decrease the color’s position, intensity, opacity, and more. Male hummingbirds, for example, have brightly colored feather patches on their throats; the coloring comes from pigments, structures that refract light, or a combination of the two. When a male hummingbird hovers near a potential mate, it modifies the angle of these feathers to create a bright, colorful display. However, when it needs to mute the colors to reduce conspicuousness, such as to avoid a predator, it modifies the angle again.

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Transform Radiant Energy (Light)

The sun is the ultimate source of energy for many living systems. The sun emits radiant energy, which is carried by light and other electromagnetic radiation as streams of photons. When radiant energy reaches a living system, two events can happen. The radiant energy can convert to heat, or living systems can convert it to chemical energy. The latter conversion is not simple, but is a multi-step process starting when living systems such as algae, some bacteria, and plants capture photons. For example, a potato plant captures photons then converts the light energy into chemical energy through photosynthesis, storing the chemical energy underground as carbohydrates. The carbohydrates in turn feed other living systems.

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Protect From Excess Liquids

While water is essential to life, too much water or other liquids can overwhelm living systems. Excess liquids can, for example, decrease a living system’s access to oxygen, promote excessive bacterial or fungal growth, or strip away soil and nutrients. To prevent the accumulation of excess liquids, living systems must control the movement of liquids across their boundaries or surfaces. They do so using waterproofing materials or structures, slowing flow, and/or facilitating flow to move the liquid away. Plant leaves, for example, commonly have waxy surfaces comprised of water-repelling chemicals to keep water from engorging the leaves or facilitating bacterial and fungal growth.

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Film from University of Central Florida has tiny protuberances that help reduce reflection and damage.

Benefits

Anti-reflective
Self-cleaning
Flexible

Applications

Contact lenses
Textiles
Medical devices
Solar energy

UN Sustainable Development Goals Addressed

Goal 9: Industry Innovation & Infrastructure
Goal 12: Responsible Production & Consumption

The Challenge

For display devices such as mobile phones and laptops, sunlight readability is essential. Sunlight readability refers to the discernibility of a display in high ambient light conditions, and is strongly correlated to surface reflection. Currently, many displays have poor sunlight readability due to high rates of light reflection, requiring boosted display luminance and, in turn, more energy.

Innovation Details

The film is made of a molded, UV-curable resin. The surface of the film contains uniform nanostructures shaped like cones, each about 100 nanometers in diameter (about one one-thousandth of the width of a human hair). These protuberances are clustered so closely together that incoming light cannot differentiate between air and the surface of the film, thus passing into the material with very little reflection. The film exhibits a surface reflection of just 0.23%, much lower than the average reflection rate of current displays, 4.4%. The antireflection film also found an application in solar cell efficiency, significantly increasing light absorption rates of photovoltaics.

Biomimicry Story

Most moths are nocturnal creatures and fly at night to avoid being spotted by predators. The eyes of a moth are unique in that they are anti-reflective, absorbing incoming light and minimizing the amount of reflection to keep the creature undetected. This anti-reflective property can be attributed to the cone-like nanostructures which are clustered on the corneal lens of the eye, reducing light reflection by creating a refractive index gradient between the air-lens interface.

See Related Content

an elephant hawk-moth photographed head on with its bring pink lower body and yellow top, long legs and big yellow eyes

Biological Strategy

Eyes Are Anti-Reflective

Moths

Eyes of nocturnal moths are anti-reflective due to nanoscale protrusions.

References

Journal article

Broadband antireflection film with moth-eye-like structure for flexible display applications

OSA Publishing

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