Micro-optofluidic Devices via Projection Micro-Stereolithography: Impact of Resin Reuse on Optical Sensing Performance

Abstract This work investigates the feasibility of recovering and regenerating uncured methacrylate-based photocurable resin from a previous 3D printing build job before being reused for a consecutive second and third build job. In detail, it was investigated the impact of the uncured resin reuse on the optical performance of 3D-printed micro-optofluidic (MoF) devices designed for absorption-based optical slug flow monitoring by comparing their optical performances when manufactured with fresh or one-time or two-times reused resin. The devices were fabricated using Projection Micro-Stereolithography with three different resin batches: fresh, one-time or two-times reused resin. Optical performance testing was conducted using an air–water slug flow. A Design of Experiment approach was employed to systematically evaluate the MoF device optical performance variability due to resin reuse. Despite Fourier Transform Infrared Attenuated Total Reflection spectroscopy has revealed minor chemical reduction in the methacrylate monomers composition of reused resins when compared to fresh one, a negligible reproducibility error in terms of optical detection performance for the MoF devices manufactured with different batches of resin was unveiled. This is attributable to stable resin cross-linking, ensuring a uniform refractive index and reliable optical sensing performance. The recovery, regeneration, and reuse of photocurable resin provide a sustainable solution to recycling challenges posed by utilization of uncured acrylate and methacrylate resins, as material waste in manufacturing can be reduced without compromising optical performance, thus promoting environmental sustainability. The presented sustainable approach allows to reduce costs, since the high cost of photopolymer resins limits large-scale manufacturing, besides minimizing environmental impact. Graphical Abstract