Photoreactive Natural Latex/ <scp> TiO ₂ </scp> Composites for Light‐Assisted <scp>3D</scp> Printing: A Bio‐Based and Stretchable Resin via <scp>TPO</scp> ‐Initiated Curing

ABSTRACT Light‐assisted 3D printing offers a powerful approach for fabricating soft elastomeric structures with high spatial resolution. However, sustainable and biocompatible resins compatible with vat photopolymerisation remain limited, especially those based on biobased latex systems. Herein, we present a photocurable resin platform derived from unmodified natural rubber latex (NRL), reinforced with titanium dioxide (TiO 2 ) nanoparticles for LCD‐based 3D printing. A key innovation lies in the successful integration of the hydrophobic photoinitiator diphenyl (2,4,6‐trimethylbenzoyl)phosphine oxide (TPO) into the aqueous latex matrix via nonionic surfactant stabilization. The formulation includes PEGMEA and Bis‐AM as reactive monomers, as well as TiO 2 to enhance both mechanical and thermal performance. The 3D‐printed PNLR‐Ti1.0 constructs demonstrated excellent shape fidelity, with a tensile strength of ~1450 kPa and an elongation of ~1100%. Thermal analysis confirmed improved thermal stability with the addition of TiO 2 . SEM/EDX revealed uniform TiO 2 dispersion at ≤ 1.0 wt%, while higher loadings caused agglomeration and mechanical decline. Cytotoxicity assays using L929 fibroblasts showed that all formulations were non‐cytotoxic, with cell viability ranging from 99.16% to 103.04%. Indeed, this work introduces a scalable, biobased, and photocurable latex resin system enabled by the incorporation of a hydrophobic photoinitiator, advancing the vat photopolymerisation of soft materials for biomedical and wearable applications.