Development of Reversible Color-Changing Three-Dimensional Structures Using a Thermochromic Resin in Digital Light Processing-Based Vat Photopolymerization.

The digital light processing-based vat photopolymerization (DLP-VPP) technology has demonstrated remarkable versatility and precision in producing complex structures across various fields. In this study, a thermochromic DLP-VPP system that achieves reversible color changes based on the temperature by combining thermochromic microcapsules (TM) with an acrylic photopolymer resin is proposed. Experiments are conducted to determine the optimal ratio of TM to achieve an ideal layer thickness without structural failure. The thermochromic properties of the TM resin composites are confirmed using differential scanning calorimetry and thermogravimetric analysis. Furthermore, experiments are performed to analyze the thermochromic reaction times at different heights, areas, and temperatures. Subsequently, a regression model is developed using machine learning techniques to predict the thermochromic reaction times. This study demonstrates the use of three-dimensional (3D) passive thermochromic sensors for visual temperature monitoring. Multimaterial DLP-VPP printing allows for the creation of 3D thermochromic QR codes, offering enhanced information security through temperature-dependent visibility. Overall, the proposed thermochromic DLP-VPP system has significant potential for applications in smart temperature sensors, anticounterfeiting, and cryptography. This study offers ideas for further research and development of functional materials for additive manufacturing.