Simple and Fast Construction of Brilliant Iridescent SiO2/PDMS Films with Switchable Color for Information Encryption and Decryption

The structural color of photonic crystals (PCs) is stable and controllable, so it is widely applied in information encryption, optical anti-counterfeiting and sensing, etc. Current studies usually combine responsive materials with PCs to modulate and switch color, then information encryption and anti-counterfeiting can be achieved. However, the construction of responsive materials is complicated, and only different single colors can be switched without switching between transparent color and iridescent color. Herein, the seed solution method was adopted to prepare polydisperse SiO 2 nanoparticles with specific normal distribution ranging from 300nm to 1100nm, and the assembled PCs were iridescent under point light. By infiltrating with polydimethylsiloxane (PDMS), the SiO 2 /PDMS iridescent film was obtained after cross-linking and curing. It is highly transparent under natural light and brilliantly iridescent under point light. In order to improve the stability and adhesion of SiO 2 PCs layer, the sandwich-structured PDMS/SiO 2 /PDMS iridescent film was prepared, with the optimal plasma processing time of 4 mins for the bottom PDMS layer. Three kinds of different polymer-based SiO 2 /PDMS iridescent films were constructed as well, of which the PET (polyethylene terephthalate) - based film was the most transparent and brilliantly iridescent. Based on the above, SiO 2 /PDMS iridescent film was patterned through screen printing and mask spraying process. Transparent and iridescent color can be quickly switched to each other under different lighting conditions, which is expected to be effectively applied in information encryption and optical anti-counterfeiting.