Inertial manipulation of bubbles in rectangular microfluidic channels

Abstract

Inertial microfluidics is an active field of research that deals with crossflow positioning of the suspended entities in microflows. Until now, the majority of the studies have focused on the behavior of rigid particles in order to provide guidelines for microfluidic applications such as sorting and filtering. Deformable entities such as bubbles and droplets are considered in fewer studies despite their importance in multiphase microflows. In this paper, we show that the trajectory of bubbles flowing in rectangular and square microchannels can be controlled by tuning the balance of forces acting on them. A T-junction geometry is employed to introduce bubbles into a microchannel and analyze their lateral equilibrium position in a range of Reynolds (1 < Re < 40) and capillary numbers (0.1 < Ca < 1). We find that the Reynolds number (Re), the capillary number (Ca), the diameter of the bubble (D[combining macron]), and the aspect ratio of the channel are the influential parameters in this phenomenon. For instance, at high Re, the flow pushes the bubble towards the wall while large Ca or D[combining macron] moves the bubble towards the center. Moreover, in the shallow channels, having aspect ratios higher than one, the bubble moves towards the narrower sidewalls. One important outcome of this study is that the equilibrium position of bubbles in rectangular channels is different from that of solid particles. The experimental observations are in good agreement with the performed numerical simulations and provide insights into the dynamics of bubbles in laminar flows which can be utilized in the design of flow based multiphase flow reactors.

Influence of Bubbles on the Energy Conversion Efficiency of Electrochemical Reactors

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“…In the case of a neutrally buoyant rigid particle suspended in a Newtonian fluid, the particle migration and final equilibrium position are determined by two opposing forces acting on the particle: these forces are the wall induced lift force that pushes the particle away from the wall and the shear-gradient induced lift force that drives the particle towards the wall, the latter resulting from the rigid particle resistance to deformation [28,64]. When the particle is deformable, its dynamics is further complicated by the additional force originating from the particle shape deformation, which depends on the elastic properties of the material (e.g., the elastic modulus G) [30,31]. Note that, the particle deformation also affects and modifies the other two forces.…”

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