2D Nanocomposite Gas-Barrier Tortuosity: Diffusion Map & Nielsen Curve

This is the 2D counterpart to the 3D tortuous-path gas-barrier scene, computing the identical Nielsen tortuosity mechanism through a top-down diffusion map and an analytic curve instead of a rendered 3D box: gas molecules random-walk upward through a film seeded with randomly placed, optionally tilted nanoclay platelets, deflecting around every collision, while a live measurement of the effective diffusivity is plotted against the Nielsen tortuosity-vs-loading curve for the current aspect ratio. Adjust filler loading, platelet aspect ratio, orientation alignment and the free diffusion rate to see when the simulation matches the textbook formula and when poor exfoliation makes it fall short.