Programmable Thermochromic Coatings via Interfacial Phase Fusion‐Separation Engineering

Abstract Thermoresponsive structural color materials hold great promise for dynamic anti‐counterfeiting and thermal monitoring, yet their widespread adoption is hindered by complex self‐assembly processes and limited scalability. Here, an innovative interfacial fusion‐separation mechanism is proposed for programmable thermochromic coatings (HPTCs), achieved by blending independently chromogenic hollow silica (H‐SiO 2 ) photonic nanopigments with eutectic phase change material (EPCM). This design circumvents traditional self‐assembly requirements while enabling commercially viable spray‐coating fabrication. Meanwhile, these HPTCs exhibit tunable transition thresholds rapid color switching (4 s) and exceptional cycling stability (>500 cycles) within a narrow physiological temperature window (33–37 °C), driven by EPCM solid–liquid transitions modulating refractive‐index contrast. A sandwich‐like process, comprising waterborne acrylic (WA) adhesive, H‐SiO 2 ‐EPCM functional, and WA protective layers, simultaneously ensures mechanical robustness and substrate versatility. The self‐assembly‐free design enables standalone anticounterfeiting labels with programmable color patterns for interactive authentication. Furthermore, the fusion‐separation‐driven thermochromic mechanism enables programmable tuning of response temperatures via fatty acid selection, allowing integration of multiple HPTCs into a versatile real‐time temperature indicator for personalized health monitoring, drinking‐water temperature warning, and electronic thermal risk detection. This interfacial engineering strategy simplifies fabrication of stimuli‐responsive optical materials, demonstrating significant potential for scalable manufacturing of commercial anticounterfeiting labels and the temperature indicator.