Fabrication and Characterization of Thermochromic Microcapsule‐Based Waterborne Inks: Toward Enhanced Functional Performance

ABSTRACT Thermochromic materials (TCMs) capable of reversible color switching within a defined temperature window hold great promise for intelligent sensing and visual temperature monitoring. Herein, we report a PMMA‐shell microcapsule‐based thermochromic waterborne ink, in which the microcapsules were prepared via suspension polymerization and encapsulate a ternary thermochromic core. The resulting microcapsules exhibit a uniform core‐shell structure with an average diameter of 30 µm and can be readily formulated into a screen‐printable ink. The ink shows stable rheology and good printability, with a fineness of 55.0 µm; it maintains a stable viscosity of 32‐40 P with a small hysteresis loop area, indicating suitability for high‐speed printing. In addition, the ink achieves a stable spreading diameter of 37 mm within 10 s, with a filament length of only 0.1 cm. The printed patterns display a distinct and reversible blue‐to‐white transition within 3 s. Notably, even after 25 heating‐cooling cycles, the ink maintains rapid thermochromic switching (response time <10 s), and the post‐cycling ΔE remains as high as 12, demonstrating reliable durability for functional printing applications such as smart packaging, temperature indicators, and anticounterfeiting.