Comparison of different methods for generating structural colors on polymer surface using femtosecond laser

The structural color preparation of polymer surfaces by multi-photon polymerization, laser induction, and replica casting were studied by femtosecond laser processing technology. The units of photoresist (SZ2080) were arranged in the form of grating to obtain angle-sensitive structural colors because of the grating diffraction effect. When the spacing was reduced to the extent that the microstructures were interconnected, the angle-insensitive structural colors could be obtained, forming the resonant metal–insulator-metal (MIM) structures after gold spraying. Diffractive coloration was obtained by femtosecond laser-induced periodic surface structures (LIPSSs) on polyimide (PI) film. The irregular period difference was attributed to the surface roughness. Moreover, the mutual adhesion of the LIPSSs resulted in the existence of intermediate periods. The mechanism of laser induction of PI depended on the amount of groups generation and fracture removal. In addition, the flexible LIPSSs were obtained by replica casting of polydimethylsiloxane (PDMS). As the strain in the X-direction increased, the corresponding reflection spectra shifted from the blue band to the red band. With the increase of the Y-direction strain, the position of the spectra remained unchanged, but the intensity of the spectra gradually decreased. Therefore, the methods would provide new technology in color display, information security, and anti-counterfeiting.