3D Helix Engineering in Chiral Photonic Materials

Abstract

Engineering the helical structure of chiral photonic materials in three dimensions remains a challenge. 3D helix engineered photonic materials are fabricated by local stratification in a photopolymerizable chiral nematic liquid crystal. The obtained chiral photonic materials reflect both handedness of circular polarized light and show super‐reflectivity. Simulations match the experimentally observed photonic properties and reveal a distorted helical structure. 3D engineered polymer films can be made that reflect both left‐ and right handed circular and linear polarized light dependent and exhibit a changing color contrast upon altering the polarization of incident light. Hence, these 3D engineered photonic materials are of interest for new and emerging applications ranging from anti‐counterfeit labels and data encryption to aesthetics and super‐reflective films.

Structural Color Materials for Optical Anticounterfeiting

“…The stratification was caused by photopolymerization initiated under linear polarized light by a dichroic photoinitiator. [ 126 ] The resultant UV‐exposed area exhibited stratified nanostructure with a periodicity equal to half of the pitch of the original chiral nematic helix, leading to selective reflection of both linearly polarized light and circularly polarized light. On the contrary, the nonirradiated area exhibited as regular chiral nematic liquid crystals with only circular polarization‐dependent reflectance.…”

“…Reproduced with permission. [ 126 ] Copyright 2019, Wiley‐VCH. b) POM of the fingerprint textured QR code observed with (upper) and without polarizers (lower).…”

Reversible Thermochromic Photonic Coatings with a Protective Topcoat

“…Glass substrates of 3 × 3 cm 2 size were prepared following a previously reported method. 41 Those of 9 × 9 cm 2 size were treated according to a similar procedure but using a different spin-coating rotation speed of 2000 rpm for 90 s.…”

Multidimensional Information Encryption and Storage: When the Input Is Light

“…Therefore, the optimized CPL-responsive materials can present different responses to LPL simultaneously. Based on the regular chiral nematic liquid crystal materials, a distorted helical structure along the z- direction was engineered by stratification of an uncrosslinked liquid crystal elastomer and a chiral liquid crystal network under the linear polarized UV light [ 99 ]. The patterned area (the cloverleaf) with stratified polymer coating could reflect both CPL and LPL, but the other regions only functioned as the regular chiral nematic liquid crystals to reflect L-CPL ( Figure 5(g) ).…”