Visualization and Characterization of Stress–Strain Behavior in Resin-Based Mechanoresponsive Sensors 3D-Printed Using Mechanochromic Cross-Linkers

This study explores the use of difluorenylsuccinonitrile-containing methacrylate (DFMA) as a mechanochromic cross-linker in a polymer system (N,N-dimethyl acrylamide, DMAA) for resin-based three-dimensional (3D) printing applications. The effect of the DFMA content on the mechanical properties and color response under mechanical stimulation was evaluated using tensile tests and color analysis. With the increase in the DFMA content, particularly when it reached 1.0 mol %, the tensile strength and mechanochromic intensity increase. DFMA incorporation also enabled the detection of localized polymer chain scission. Rheological analysis demonstrated that the DFMA–DMAA mixture exhibited a favorable photocuring behavior, making it suitable for liquid crystal display 3D printing. Moreover, the optimal 3D printing conditions were determined to minimize the dimension distortion of the printed specimens. A correlation between the red–green–blue (RGB) values and the stress–strain behavior was established based on the color analysis, providing a comprehensive understanding of the mechanochromic response of the material. These findings highlight the potential of P(DFMA–DMAA) for creating customizable, mechanochromic 3D-printed sensors with improved mechanical properties for various applications.