Low-intrusive colour-enhanced pattern coating of plastics for fluid-mechanics laboratory experiments

Plastic transport experiments have been conducted under laboratory conditions over the past five-year period. The primary objective of these experiments is to obtain physical insights into the interactions among fluids, plastics, and solids. These insights aim to facilitate the upscaling of findings to riverine or maritime environments for predictive purposes. Despite the significant progress, challenges persist, notably in tracking plastic particles, potentially employing multi-camera setups. Traditional imaging methods, such as contrast-based detection or moving-object algorithms (based on selected computer vision or background differentiation techniques), can encounter several limitations. For instance, samples with low contrast relative to the background are more susceptible to errors, and the slow movement of samples can yield weaker signals compared to fluctuating light reflections in the area of interest. Additionally, 3D tracking can introduce compounded errors across multiple cameras, leading to amplified errors.

In response to these difficulties, our research introduces a novel colour-based contrast enhancement technique, based on a multi-colour water-proof coating for plastic samples. Our protocol leads to coating added masses remaining below 1%, while facilitating the precise detection of transparent and deformable plastics. We present the current limitations in detectability, including light dependency, and discuss the potential advancements enabled by our proposed methodology.