A droplet sits on a hydrophobic dielectric coating over a grid of electrodes with no applied field, beading up at a high rest angle θ₀. Grounding the droplet and biasing one electrode creates an electric field across the thin dielectric that locally lowers the effective solid-liquid interfacial energy — the Young–Lippmann equation:
cos θ(V) = cos θ₀ + (ε₀ε_r)/(2γd) · V²
- θ(V) drops toward that electrode, pulling the contact line and dragging the whole droplet one cell over — repeat on neighboring electrodes to walk it anywhere on the grid.
- Split activates electrodes on both sides at once: the footprint stretches, the neck thins, and surface tension pinches it into two independent droplets.
- Merge brings two droplets onto adjacent electrodes until their contact lines touch and coalesce into one, volumes summing (r³ adds, since surface tension conserves total liquid volume).
Real EWOD (electrowetting-on-dielectric) devices saturate around 60–70° regardless of how much higher the voltage climbs — the model below caps θ(V) at that floor, just like the physical effect.