Fluoropolymer Coating For Invisible Plastic Optics

Acrylic and polycarbonate lenses are used in a wide range of optical applications; however, the inorganic antireflection (AR) coatings that improve the performance of glass lenses are difficult to apply to plastic optical surfaces. Researchers created a method for coating these plastic lenses with a fluoropolymer that adheres well and even makes the surfaces appear invisible to the viewer.

AR coatings may improve the efficiency of solar panels that use plastic lenses to concentrate sunlight, in addition to improving optical components. Other potential applications include reducing reflections in security camera domes and virtual-reality equipment.

The key to creating this coating is to deposit two different types of molecules onto the plastic lens surfaces, rather than just one. The researchers incorporated a “sacrificial” molecule – a type of organic semiconductor—while evaporating the amorphous fluoropolymer onto the substrate.

Fluoropolymer chains break up and repolymerize on the substrate around the semiconductor molecules during evaporative deposition. When the substrate lens surfaces are washed with a solvent such as isopropyl alcohol, the sacrificial molecules dissolve, leaving behind a nanoporous fluoropolymer coating. The method is similar to that used in tissue engineering, in which dissolvable particles known as porogens are used to create a porous structure for supporting cells.

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