Bubble control, levitation and manipulation using dielectrophoresis

Abstract

Bubbles attached to surfaces are ubiquitous in nature and in industry. However, bubbles are problematic in important technologies, including causing damage to the operation of microfluidic devices and being parasitic during heat transfer processes, so considerable efforts have been made to develop mechanical and electrical methods to remove bubbles from surfaces. In this work liquid dielectrophoresis is used to force a captive air bubble to detach away from an inverted solid surface and, crucially, the detached bubble is then held stationary in place below the surface at a distance controlled by the voltage. In this “levitated” state the bubble is separated from the surface by liquid layer with a voltage-selected thickness at which the dielectrophoresis force exactly counterbalances the gravitational buoyancy force. The techniques described here provide exceptional command over repeatable cycles of bubble detachment, levitation, and re-attachment. A theoretical analysis is presented that explains the observed detachment-reattachment hysteresis in which bubble levitation is maintained with voltages an order of magnitude lower than those used to create detachment. Our precision surface bubble removal and control concepts are relevant to situations such as nucleate boiling and micro-gravity environments, and offer an approach towards "wall-less" bubble microfluidic devices