Takayuki Nakanishi

Black thin layers generate strong structural colors: a biomimetic approach for creating one-dimensional (1D) photonic crystals

We report a simple, novel method for obtaining structurally colored films consisting of poly(1,2-butadiene) (PB) and Os multi-layers that mimic the surface structure of jewel beetle elytra. Strong color reflection was achieved by interference of light at the interface between the multi-layers. Active control of the reflection peaks was achieved by swelling the PB layers with solvent, and photopatterning of the composite film was also performed.

Patterned metallic honeycomb films prepared by photo-patterning and electroless plating

By photo-patterning of photochromic honeycomb films and electroless plating, patterned silver honeycomb films were prepared. A photochromic amphiphilic copolymer containing spiropyran was successfully synthesized, and used for honeycomb film preparation. After photo-patterning of the photochromic honeycomb film, the photo-patterned regions were metallized by electroless plating. After solvent vapor treatment, only the metallized honeycomb region kept its structure.

Flexible, Optically Transparent, and Conductive Line-and-Space-Patterned Films Prepared by Using a Simple Dewetting Process of Gold Nanoparticle Dispersions

Flexible, optically transparent, and conductive line-and-space patterns were prepared by a simple coating of gold nanoparticle (Au NP) dispersions onto both glass and flexible polymer substrates. The Au NP dispersion was injected into the gap between the two solid substrates, and then the upper substrate was straightly moved by using a hand made apparatus equipped with a stepping motor. Owing to the dewetting of the Au NP dispersion on the substrate, line-and-space patterns were spontaneously formed from the receding meniscus of the Au NP dispersion supplied from the edge of the upper substrate. After sintering, the line-and-space-patterned film showed optical transparency (more than 80%) and in-plane anisotropic conductivity (3.82×103 Scm-1).

Structural colors from multi-layered films containing black thin layers

We have demonstrated the simple preparation of structurally colored composite films by stacking alternating Os and PB layers. Os has a much higher refractive index than PB, which causes the strong reflection at the interface between these two materials. Strong reflection colors were observed because of the interference between the multi-layers. Active control of the reflection peaks was achieved by swelling the PB layers. From these results, we conclude that black thin layers enhance the reflection of structural colors.