The electrostatically forced Faraday instability - theory and experiments

Theoretical predictions are presented for the resonant instability in a two-fluid viscous, leaky dielectric system subject to oscillatory electrostatic forcing. It is shown that the instability arises as a result of resonance between the parametric frequency of the imposed oscillatory electric field and the system’s natural frequency. This study is the first of its kind where a hydrodynamic model is presented assuming a pair of fluids in a viscous leaky dielectric system. In addition to a linear stability analysis, this study also presents validating experiments that provide excellent agreement with the predictions of the model. Finally, an important outcome of the analysis and experiments is a novel way to measure interfacial tension between fluid bilayers. This is due to the contribution of electrostatic terms to the system’s natural frequency which act to counter gravitational effects and amplify the importance of interfacial tension.