Harmless photonic crystal tattoo with angle‐independent structural color based on SiO2 nanoparticles and silk fibroin

Abstract Owing to the potentially irritant nature of chemical ingredient in cosmetics, harmless photonic crystal tattoo (HPCT) materials with angle‐independent structural color have shown great promise in cosmetic industry. However, it still remains a challenge to produce artificial photonic crystal materials with good adherence to biological cutaneous tissue. Herein, a photonic crystal tattoo based on SiO 2 nanoparticles/silk fibroin (SiO 2 NPs/SF) is reported. With the SF solution addition of 55.8%, the 180° peel strength and nanoindentation adhesion force of product increased by 427.4% and 103.9%, respectively. Finally, as proof of concept, its applications for creating tattoo with optical pattern on artificial skin were shown. Based on its superior adhesion, harmlessness, and environmental friendliness, the product may be a promising candidate material for the cosmetic industry.