The development of sensor materials with antimicrobial properties is crucial for advancing biomedical applications, particularly in sterilization and wound care. In this study, we present a novel approach to fabricating a multifunctional sensor material by integrating cellulose nanocrystals (CNCs) with antimicrobial photodynamic inactivation (aPDI) and poly[2-(tert-butylamino)ethyl methacrylate] (PTA) within a 3D-printed composite. CNCs, known for their biocompatibility and functional surface chemistry, serve as an ideal platform for embedding antimicrobial agents. Erythrosine, a photosensitizer, is used to activate aPDI, whereas PTA provides additional antimicrobial efficacy. The sensor material’s antimicrobial performance was evaluated, demonstrating the complete inactivation of Escherichia coli and Staphylococcus aureus under green and white light irradiations. The integration of CNCs with aPDI and PTA enhances the material’s sensing capabilities, allowing for the real-time monitoring of microbial contamination. This composite material is a promising candidate for applications in wound care and sterilization, providing both structural support and antimicrobial functionality.