Light Based 3D Printable Photochromic WO3 Polymer Gel Nanocomposites for Heat Management and Decorative Applications

Materials with functionalities such as photochromicity are needed to extend the palette of materials for additive manufacturing. Herein, gel nanocomposites (gel NCs) with photochromic properties are designed for light-induced 3D printing. The photochromic resin is prepared by using a photocurable acrylic formulation, containing tungsten oxide nanoparticles (WO₃ NPs) in the presence of aqueous and alcohol plasticizers. After photopolymerization, gel NCs transition reversibly from a highly transparent colorless state to a dark blue-colored state when exposed to UV light. The addition of ethylene glycol to water as a co-plasticizer and a lithium salt improves the gels coloration kinetics while providing anti-freezing and anti-drying capabilities. The gels demonstrate high luminous transmission (T_lum) of 89.24% and optical modulations (ΔT_sol) of up to 75.96%, with a coloration speed of less than 1 min. Energy-saving simulations show that the WO₃ gel NCs can be used for heat management applications. The preparation of costume-made 3D designs using the photocurable resin with a digital light processing (DLP) 3D printer, demonstrates that the resin can be used for the additive manufacturing of photochromic gels.