Design of Polymeric 3D Printable Materials for THz Technology Applications

Terahertz (THz) radiation is rapidly gaining attention for applications in biomedical diagnostics, security, and wireless communication. Polymers play a central role in advancing THz technologies, as they are ideal for lenses, filters, waveguides, and metasurfaces. However, material selection is driven by commercial availability rather than by the rational design of their composition, and progress is hindered by the limited availability of polymers that combine low THz losses with high printability. To address this problem, the relationship between polymer composition and THz transparency in photocurable resins is here investigated, establishing practical guidelines for tailoring THz response through resin composition. A comprehensive framework is developed to predict THz properties based on key structural features, including heteroatoms, cyclic structures, secondary forces, and the carbon-to-oxygen (C/O) ratio. In particular, (meth)-acrylic resins with aliphatic backbones exhibit predictable behavior, enabling the estimation of their THz response directly from the C/O atomic ratio. Using the best-performing formulations, photonic crystals for THz modulation were fabricated via digital light processing (DLP) 3D printing. These devices are used to demonstrate how geometric parameters, fabrication precision, and material properties influence the THz devices' response. Comparisons between THz-optimized formulations and commercial resins highlight the importance of combining high printability and THz transparency in the fabrication of functional devices, demonstrating that proper resin design enables the decrease of the absorption coefficient up to 5 cm^-1 at 1THz (vs 19-30 cm^-1 of commercial resins usually employed for 3D-printed THz devices), maintaining a sufficient printability, resulting in an extension of the range of controllable response of the photonic crystals up to 2 THz, well beyond the sub-0.5 THz limit typically reported in the literature for similar structures. This material-driven approach establishes a rational pathway for designing polymers tailored for THz applications while enabling the fabrication of technologically relevant devices with accessible and low-cost 3D printing.