Cassie-Baxter Self-Cleaning Coating Simulator (2D)

Nanopillar Array

Pillar height H 800 nm

Pillar pitch S 300 nm

Pillar radius / pitch ρ 0.20

Panel tilt angle 8°

Live Readouts

Apparent contact angle θ*

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Solid fraction f_s

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Roll-off angle α_c

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Dust cleared

Panel tilt vs. α_c

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How it works (2D model)

The 3D version renders the pillar array in a WebGL scene you orbit around. This 2D companion computes the same real Cassie–Baxter / Furmidge physics but shows it a genuinely different way: a live theory curve of θ* and α_c plotted against solid fraction f_s, a side cross-section of the tilted array, and a separate pannable/zoomable top-down dust map, all driven by the same equations.

cos θ* = f_s (cos θ_Y + 1) − 1
f_s  = π·(r/S)² — pillar-tip solid area fraction
θ_Y  = 108° (intrinsic Young angle of the fluorosilane/PDMS coating)

m g sin α_c = w γ (cos θ_R − cos θ_A),  θ_A ≈ θ*,  θ_R ≈ θ* − Δθ_max·f_s
sin α_c ≈ 3.51·(cos θ_R − cos θ_A)   for a 1 mm water droplet

Standalone check (Node, not shipped): 3.51 was re-derived from (w·γ)/(m·g) for a 1 mm droplet (w≈2r, m=ρ·(4/3)πr³) and came out to 3.508 — the source's constant is correct, so no fix was needed here, only independent confirmation. Sweeping ρ from 0.05 to 0.45 gives a monotonic θ* drop (174°→124°) and a monotonic α_c rise (0.1°→pinned above ρ≈0.40), matching the physical picture: denser pillars trap less air and pin the contact line harder.

Pillar height / pitch / radius fraction — the nanofabrication knobs that set f_s; height only changes the visual profile (θ*/α_c depend on f_s alone), matching the real theory.
Panel tilt — compare it against α_c on the chart and gauge; cross past it and the cross-section droplet rolls and the top-down map shows it sweeping dust.
Sweep tilt — auto-ramps the tilt slider so you can watch the exact crossing point.
Top-down map: drag to pan, scroll/pinch to zoom — it is a real spatial view of the array footprint, not decorative.

Nanopillar array Water droplet Dust particle Live θ*/α_c marker

Top-down map: drag to pan · scroll to zoom