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PolskiDigital Microfluidics: Electrowetting Droplet Actuator (2D)
Top-down EWOD chip: click a droplet, then an adjacent electrode — the Young-Lippmann equation lowers the local contact angle there and drags, splits or merges the droplet across the grid, with no channels, pumps or moving parts.
This 2D companion runs the same constant-volume spherical-cap droplet model as the 3D original, viewed straight down onto the electrode grid: activating an electrode lowers the contact angle there via the Young-Lippmann equation, which this top-down view draws directly as the droplet's footprint circle growing on that side and dragging the whole droplet one cell over. Switch to Split mode to stretch a droplet into an ellipse and pinch it into two, or Merge mode to coalesce two droplets into one, with live readouts for both contact angles and a running count of moves, splits and merges.
2D top-down electrowetting-on-dielectric (EWOD) lab: the Young-Lippmann equation drives the contact angle, a constant-volume spherical-cap model sets the footprint radius, and click-to-actuate controls move, split and merge droplets across a 6×4 electrode grid.
2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install
cos θ(V) = cos θ0 + (ε0 εr)/(2γd) · V² — it gives the contact angle θ(V) a droplet forms on an energized electrode as a function of the applied voltage V, the dielectric coating's permittivity and thickness, and the liquid's surface tension γ.
Only the electrode directly under one side of the droplet is energized, so the contact angle — and the outward pull on the contact line — drops on that side only. The resulting asymmetric force drags the whole droplet toward the active electrode, one grid cell at a time.
Real EWOD devices hit contact-angle saturation, typically around 60-70°, where further voltage no longer lowers the angle — thought to be caused by charge trapping and dielectric breakdown risk at the contact line. This model caps θ(V) at that floor to match the physical effect.