Deformation dynamics of a thin liquid film driven by dielectrophoretic forces*

The controlled deformation of thin liquid films can be leveraged toward the creation of adaptive optical elements. We here present a combined theoretical and an experimental study of the dynamics of a thin liquid film subjected to a dielectric force distribution created by surface electrodes.  We model the spatial electric field produced by a pair of parallel electrodes and calculate the Maxwell stresses on the interface. These stresses serve as boundary conditions for the fluids' momentum equations, resulting in an evolution equation which we approximate under the longwave approximation. For validation of our theoretical framework, we developed a holography-based experimental setup that enables high frame-rate measurements of microscale deformations. We actuate the liquid using different patterns of microfabricated electrodes at the surface of the fluidic chamber and different time-dependent actuation functions and observe its temporal response.