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.
Ren et al. (Sun,) studied this question.