Vat photopolymerization of bio-derived conductive composites for smart devices with Joule heating capabilities

This study explores the use of a bio-based photopolymerizable monomer, acrylate polyglycerol, for fabricating smart 3D-printed objects Vat Photopolymerization (VPP) technology. Derived from vegetable oil saponification or microbial fermentation, this monomer serves as a photocurable building block after acrylate functionalization. Conductive fillers, including silver, copper, nickel powders, and mechanically recycled carbon fibers (RCF), were incorporated to enhance electrical conductivity and Joule heating capabilities. These formulations combine the sustainability of bio-derived materials with advanced functionalities for smart applications. Characterization techniques such as FT-IR, photo-DSC, rheology, DMTA, electrical conductivity analysis, and thermal imaging revealed that while increasing filler content reduces polymerization rate and increases viscosity, it significantly improves electrical conductivity and, in some cases, thermal-mechanical properties. Notably, Ag- and RCF-filled formulations enabled effective Joule heating, achieving uniform heat distribution. As a proof-of-concept, a smart wearable ring was 3D-printed using a 50%wt Ag formulation, reaching therapeutic temperatures (60 °C) with minimal energy input (1–3 V). The ability to manufacture geometrically complex, energy-efficient devices through 3D printing, combined with the sustainability of bio-based resins, highlights the potential of these materials for medical, electronic, and smart applications. This research bridges sustainability and innovation in additive manufacturing, paving the way for high-performance, eco-friendly solutions.