title: Broadband and crack-free antireflection coatings by self-assembled moth eye patterns.
abstract: We report broadband and quasi-omnidirectional antireflective (AR) structures inspired to the nipple arrays of moth eyes. These nanocoatings, based on thin elastomeric films, are prepared by simple self-assembly processing of a co-polymer specifically designed to this purpose, and PDMS replica molding. Typically, their surface is covered by a compact distribution of hemispherical nanodomes of about 250 nm in diameter and about 100 nm in height. When these novel nanostructures are applied on a single glass surface, a maximum of 2% transmission enhancement (equivalent to a 50% reduction of the reflected component) towards wavelengths ranging from visible to near IR region is obtained. A considerable AR power is observed also at a wide range of incident angles ranging from normal to 50°. These properties could be attributed to an optimized graded refractive index profile resulting from the randomly distributed and close-packed nanodomes. Moreover, thanks to their elastomeric nature, these crack-free films can be easily applied on glass, as stickers, and periodically replaced, thus offering the possibility of easy dirt removal from an optical device.
authors.affiliation: CNR Istituto per lo Studio delle Macromolecole (ISMAC) , via E. Bassini 15, 20133 Milano, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Galeotti
authors.forename: Franco
authors.initials: F
authors.lastname: Trespidi
authors.forename: Gianluca
authors.initials: G
authors.lastname: Timò
authors.forename: Mariacecilia
authors.initials: M
authors.lastname: Pasini
mesh_terms: D000818:Animals; D005123:Eye / Q000737:chemistry; D008422:Materials Testing; D009036:Moths; D049329:Nanostructures / Q000737:chemistry*; D055096:Optical Devices; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D012031:Refractometry; D013499:Surface Properties
chemical_list: D011108:Polymers