New Curable Polymers Refractive Index Matched to Water

Refractive index matching is a widely used strategy used in experimental fluid dynamics research to visualize flow around solid models without optical distortion caused by refraction at liquid-solid interfaces. This is traditionally achieved by pairing solid materials with matching-index fluids, like acrylic with para-cymene. However, fluids other than water often pose significant drawbacks, including high cost, toxicity, and incompatibility with laboratory facilities. To address these limitations, we developed a solid transparent material with a refractive index matched to that of water, 1.333, enabling high resolution measurements with water as the working fluid. The material is based on fluorinated polymer backbones formulated into a curable liquid resin. This resin can be solidified via UV or thermal curing in the presence of appropriate initiators. Mechanical performance is enhanced through the incorporation of additives to improve hardness and tensile strength, allowing the material to endure experimental flow conditions. Current work focuses on optimizing both the refractive index and mechanical properties of the cured polymer to achieve a set of durable, optically transparent solids suitable for flow visualization in water-based experiments in different conditions.