In-situ fabrication of WO3 nanoparticles for photochromic inks toward thermo-erasable and rewritable applications
Photochromic materials with rapid, reversible, and controllable color changes are of significant interest for rewritable media. However, conventional systems often suffer from slow bleaching kinetics, complex synthesis procedures, and poor durability. Herein, we report a cost-effective and environmentally benign thermo-erasable photochromic ink prepared via a facile in-situ synthesis strategy. The approach enables the formation of WO 3 nanostructures confined within a polyethylene glycol (PEG) matrix without requiring high-temperature processing or toxic precursors. The resulting composite exhibits efficient photochromic coloration within approximately 1 min under intense UV irradiation and is also capable of coloration under low-intensity illumination (10 W m −2 ). Notably, the reversible crystalline to amorphous phase transition of PEG upon mild heating creates dynamic free volume and diffusion pathways, promoting oxygen penetration and facilitating rapid thermal bleaching within 10 min. The material demonstrates excellent durability exhibiting stable performance over 200 repeated write–erase cycles. The material shows reliable bending robustness on flexible substrates. In addition, applying a thin PDMS over-coating provides effective waterproof protection, allowing the device to maintain stable optical performance during continuous exposure to high-temperature (80 °C) and high-humidity (80 %) conditions for 72 h. This accelerated test corresponds to approximately 1.2 years of operation at 20 % relative humidity, with the maximum coloration loss remaining below 8 %. This integrated design successfully overcomes the limitations of traditional photochromic systems by achieving both long-lasting coloration and actively controllable decoloration. Overall, this work establishes a scalable platform for sustainable, high-performance rewritable optical media based on nanoscale structural engineering and controlled oxidation regulation.
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