Electrowetting on Semiconductors

Applying a voltage difference between a conductor and a sessile droplet sitting on a thin dielectric film separating it from the conductor will cause the drop to spread. When the conductor is a good metal, the change of the drop’s contact angle due to the voltage is given the Young-Lippmann equation. Here we report experiments with lightly-doped, single crystal silicon as the conductive electrode. We derive a modified Young-Lippmann equation that includes effects due to the semiconductor and contact line pinning. We show that light induces a non-reversible wetting transition, and that our model agrees well with our experimental results.