UV-curable Acryl-Polyurethane for Human-Compatible Flexural 3D Printing Structures

An acryl-functionalized urethane prepolymer series with various compositions were synthesized using polyethylene glycol (PEG) and hexamethylene diisocyanate (HDI). Optimizing blending formulation for human-compatible 3D printing structures was based on MTT assays for cytotoxicity. The MTT assay was used to determine the biocompatibility of acryl-urethane (AU) resin for mammalian HaCaT cells. In the case of polyol, the most important component of the resin, treatment with poly(tetramethylene ether) glycol (PTMG) and polycaprolactone diol (PCL) induced concentration-dependent cytotoxicity, whereas PEG showed no cytotoxic effect. AU resin was designed by the addition of 2-hydroxyethyl methacrylate (2-HEMA) as a suitable material for digital light processing (DLP) 3D printing. The optimizing photo-initiator and additive were selected by UV-spectroscopy. The formulation containing the UV-curable AU resin and photo-curable additives was exposed to 405 μm UV radiation to produce the 3D structures. The effects of the photo-initiator/multifunctional acrylate value and UV absorptive power on the 3D printing performance were evaluated in terms of the mechanical properties and dimensional resolution. The surface properties of the 3D structures were tuned by controlling the photo-initiator type and composition in the AU resin. The resolution quality of the 3D printed wearable bands showed distinct differences by UV curing time, viscosity, and exposure amount. Overall, this UV-curable AU resin can be a promising prepolymer for the DLP printing of flexible photo-resin for biocompatible and photo-curable applications.