3D Lotus Effect Simulator — Cassie-Baxter Droplet on Nanopillars

Lotus Effect — 3D (Cassie–Baxter)

Intrinsic angle θ₀ 104°

Solid fraction f_s 0.15

Pillar height h 2.2 µm

Droplet size 1.0×

Apparent θ*

–

Roughness r

–

Air fraction

–

Regime

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How it works

Here the same micro-pillar field is a real 3D grid you can orbit around. In the Cassie–Baxter state the droplet — an actual spherical cap mesh, not a sprite — rests on the pillar tops with visible gaps of trapped air beneath it, wetting only the solid fraction f_s of the footprint. Flip to Wenzel and the cap sinks to the substrate, so the liquid instead floods every groove and roughness amplifies the flat surface's native wettability.

Cassie–Baxter:  cos θ* = f_s(cos θ₀ + 1) − 1
Wenzel:         cos θ* = r · cos θ₀   (r = actual/projected area ≥ 1)
cap geometry:   a = R sin θ*,  H = R(1 − cos θ*)

Intrinsic angle θ₀ — the material's own wettability on a flat surface.
Solid fraction f_s — how much of the pillar-array footprint is actual solid; the Cassie cap mesh is rebuilt every time it changes.
Pillar height h — the instanced pillar array's height, which drives the Wenzel roughness ratio r.
Drag to orbit — rotate freely around the droplet to see the trapped-air gaps from the side.

Real-world relevance: engineered superhydrophobic coatings replicate exactly this pillar geometry at nanoscale to make self-cleaning glass, anti-icing aircraft surfaces and anti-fouling marine paints — the droplet never wets enough solid to stick.

Water droplet (spherical cap) Pillars (InstancedMesh) Trapped air pocket

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3D Lotus Effect Simulator — Cassie–Baxter Droplet on Nanopillars