This simulator computes the real Young equation cos θ = (γ_sv − γ_sl) / γ_lv from three interfacial tensions you set directly, then draws the resulting circular-cap droplet with correct area-preserving geometry and animated tension-vector arrows at the contact line. Switch to Wenzel (cos θ* = r·cos θ, roughness amplifying native wetting) or Cassie-Baxter (cos θ* = f·(cos θ+1) − 1, air trapped beneath the drop) to see how surface texture — not just chemistry — can push a droplet all the way to the superhydrophobic lotus-leaf regime.
Why water beads up on some surfaces and spreads flat on others: the contact angle is set by a mechanical balance of three surface tensions at the three-phase line, and can be dramatically modified — without changing the surface chemistry — by adding micro-scale roughness.
Pick a Material preset (glass, steel, paraffin, PTFE, lotus leaf) or drag γ_sv, γ_sl, γ_lv directly; choose Smooth, Wenzel, or Cassie-Baxter surface texture and adjust Roughness ratio r or Solid fraction f; watch the Young angle θ, Apparent angle θ*, and Wetting state update live, and use Droplet volume, Pause, and Reset to control the animation.
The lotus leaf's famous water-repelling "lotus effect" isn't primarily a chemical property — its wax coating alone is only moderately hydrophobic — the real trick is microscopic pillar-like texture that traps air pockets under droplets (the Cassie-Baxter state), pushing the apparent contact angle above 150°.
It's the mechanical force balance at the three-phase contact line where solid, liquid, and vapour meet: cos θ = (γ_sv − γ_sl) / γ_lv, where the three γ terms are the solid-vapour, solid-liquid, and liquid-vapour surface tensions.
In the Wenzel state the liquid fully penetrates surface roughness and roughness simply amplifies the surface's native wetting tendency (cos θ* = r·cos θ); in the Cassie-Baxter state the liquid sits on top of trapped air pockets between surface features, so the apparent wetting is a weighted average between the solid and air (cos θ* = f·(cos θ+1) − 1).
Because the Wenzel and Cassie-Baxter relationships both amplify whatever the smooth-surface Young angle already favours — a naturally hydrophobic surface (θ>90°) becomes more hydrophobic with roughness, while a hydrophilic one becomes more wetting, since roughness increases the true contact area or lets air get trapped underneath.
Surfaces with an apparent contact angle above about 150° are classified as superhydrophobic, meaning droplets bead up almost into perfect spheres and roll off with minimal contact — the regime achieved by textured, low-surface-energy materials like the lotus leaf or engineered PTFE coatings.
They represent the three interfacial tensions pulling on the contact line simultaneously — γ_lv along the droplet surface, γ_sv along the dry solid surface, and γ_sl along the wetted solid surface — and the droplet settles at the angle where these three forces are in equilibrium.