Triggering the Splitting Dynamics of Low-Viscous Fingers through Surface Wettability Inside Bifurcating Channel

This work presents the splitting dynamics of low-viscous fingers inside the single bifurcating channel through the surface wettability of daughter branches. The propagation of low-viscous fingers inside branching microchannels have importance in many applications, such as microfluidics, biofluid mechanics (pulmonary airway reopening), and biochemical testing. Several numerical simulations are performed where a water finger propagates inside the silicon oil-filled bifurcating channel, and at the bifurcating tip, it splits into two fingers and these fingers propagate into the separate daughter branches. It is noticed that the behaviour of finger splitting at the bifurcating tip depends upon numerous parameters such as surface wettability, capillary number, viscosity ratio, and surface tension. This study aims to trigger the behaviour of finger splitting through the surface wettability of daughter branches θ1,θ2. Therefore, a series of numerical simulations are performed by considering four different surface wettability configurations of daughter branches, i.e., θ1,θ2∈78°,78°;78°,118°;78°,150°;150°,150°. According to the results obtained from numerical simulations, finger splitting may be categorized into three types based on splitting ratio λ, i.e., symmetrical splitting, nonsymmetrical splitting, and reversal (no) splitting. It is noticed that the surface wettability of both daughter branches is either hydrophilic 78°,78° or superhydrophobic 150°,150°, providing symmetrical splitting. The surface wettability of one of the daughter branches is hydrophilic and another is hydrophobic 78°,118°, providing nonsymmetrical splitting. The surface wettability of one of the daughter branches is hydrophilic and another is superhydrophobic 78°,150°, providing reversal splitting. The findings of this investigation may be incorporated in the fields of biochemical testing and occulted pulmonary airways reopening as well as respiratory diseases such as COVID-19.