Mass-manufactured diffraction pattern enables large-scale spectroscopic, temporal, and spatial measurements of fluid movement and mixing

• Monitors 70 L fluid volumes with spatial, temporal, and spectral resolution. • Tracks contaminant 3D shape, size, and movement in real time. • Measures plume dispersion in freshwater and seawater continuously. • Uses mass-manufactured diffraction film for scalable mid-area sensing. Monitoring fluid movement and mixing is essential for assessing environmental pollution and optimizing industrial processes; however, mid-scale tracking is often limited by the high costs of sensor networks or the low resolution of satellite imaging. Here, we introduce a mass-manufactured nanotextured diffraction surface as a scalable mid-area sensor for real-time, spatially and temporally resolved fluid dynamics measurements. By positioning the diffraction surface along the back and sidewalls of a 70 L water tank, we track dye dispersion and reconstruct three-dimensional fluid motion using image analysis, enabling direct comparisons between freshwater and saltwater environments for over 600 s. Our results demonstrate the potential of this approach as a novel, low-cost method for continuous, mechanistic monitoring of fluid mixing dynamics.