Theory of the liquid film motor

Abstract

The liquid film motor is a freely suspended liquid film placed between two capacitively coupled plates that rotates when an electric current is passed through it. Here we propose a theory for its rotation mechanism based on thin film electroconvection. The capacitively coupled plates induce free charges on the surfaces of the film, and the electric field on the film exerts a force that induces rotation. Results of the proposed theory and simulation are in good agreement with the experiments in different properties of the liquid film motor.

Procedures used in electrokinetic investigations of surfactant-laden interfaces, liquid films and foam system

“…A good agreement was found between the numerical simulations and the experimental results [20]. In [18], simulations were undertaken to explain the theory of the liquid film motors and to extend the understanding.…”

“…A liquid film motor is an experimental set-up where an external electric field (AC or DC) is applied to a free liquid film [13,15,18,19], and electrically induced rotation of the liquid is achieved by Electro-Hydrodynamical (EHD) effect. The free liquid film frame is kept horizontal in most cases to reduce the effect of the gravity.…”

Electroosmotic Flow in Free Liquid Films: Understanding Flow in Foam Plateau Borders

“…In the past few years, several publications have reported fluid flow in a free liquid film using different procedures [8][9][10][11][12][13][14][15][16]. A liquid film motor [8][9][10][11][12][13] has been reported, where a thin, freely suspended liquid film placed between two capacitor plates under a DC power source resulted in a complex motion of the fluid due to uneven charge distribution across the film. In [14,15], film stability was improved by electroosmotic flow counterbalancing the drainage of a soap bubble [14] and a free liquid film [15].…”

Electroosmotic flow measurements in a freely suspended liquid film: Experimhents and numerical simulations

“…Several investigations reported manipulation of fluid in free liquid films by various mechanisms. A liquid film motor has been reported , where a free liquid film placed in between two capacitively coupled plates is connected to a DC power source. The electric field applied to the liquid exerted a force on the induced free charges accumulated on the surface of the film and caused the fluid to undergo complex motion.…”