Liquid films play a crucial role in bubble lubrication and related engineering applications, and also serve as a soft nanofluidic channel with potential applications for neuromorphic computing. We previously demonstrated that an external electric field can modulate film thickness, thereby creating a resistance-switchable system that resembles a soft memristor and is relevant to bubble lubrication. However, the electrohydrodynamics of liquid films under an external electrical field remained unclear. In this work, we developed an analytical model of liquid-film dynamics, incorporating Maxwell stress, disjoining pressure, and Laplace pressure at a surfactant-covered liquid-vapor interface. We derived the equilibrium film thickness under an electric field to explain the observed conductance rectification, which arises from film thickening or thinning under different bias polarities. Furthermore, we analyzed the electrohydrodynamic response of the film under a triangular voltage sweep, revealing frequency-dependent current hysteresis and the effects of voltage amplitude. This study offers theoretical insights into the electrohydrodynamics of the liquid film for applications in soft memristors and bubble lubrication.

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• Electrohydrodynamic effects
• Electrokinetic flows
• Thin fluid films
• Microbubbles
• Stokes equations