Predicting Actuated Contact Line Pinning Forces and the Elimination of Hysteresis under AC Electrowetting

An accurate description of contact angle hysteresis in AC electrowetting is important for a wide range of practical electrowetting applications. This work demonstrates that electrowetting actuated advancing contact angles and the reduction of contact angle hysteresis in AC electrowetting are better predicted when characterizing the advancing electrowetting force by its root mean square (rms) value as opposed to its time-averaged or maximum values. Characterizing the electrowetting force by its rms value allows the transient electrowetting force to exceed the pinning force for some amount of time overcoming the inertial effects at the contact line before advancement. This is opposed to the maximum force characterization which implies that inertial effects can be neglected at the contact line resulting in immediate advancement when the forces are unbalanced.