A wettability pattern-mediated trapped bubble removal from a horizontal liquid–liquid interface

Abstract

The passage of a bubble through an immiscible horizontal liquid–liquid interface has a wide range of applications, from chemical processes to microfluidic devices. Buoyancy governs this passage of the bubble, and at the liquid–liquid interface, the bubble encounters a downward pulling force due to surface tension. Depending on the volume of the bubble, it may pass through or become trapped at the interface. In this study, for the first time, we proposed the idea of trapped bubble removal from a liquid–liquid interface with the aid of a wettability-patterned cone. The bubble detachment dynamic is investigated using numerical results and theoretical analysis. The effect of fluid properties and cone parameters on bubble detachment has been extensively studied. It is found that density contrast (ρr) and viscosity contrast (μr) of both the liquids, surface tension ratio (σr), bubble diameter (d0), wettability of the cone (θ), and cone angle (α) play a crucial role in bubble detachment. Here, we studied the effect of each parameter on the bubble detachment and, based on that, identified two distinct regimes, e.g., detached regime and non-detached regime. The regime map is represented by two non-dimensional groups βco and ψ, which are functions of Bond number (Bo), Ohnesorge number (Oh), α, and θ. Furthermore, the transport characteristics of the bubble on the cone after the detachment indicate that the bubble velocity decreased as it moved from the narrower to the wider section of the cone. These findings could be useful in the removal of trapped bubbles from a liquid–liquid interface in small-scale chemical industries.