Study on droplet breakup characteristics in the Y-shaped microchannel based on the accelerated volumetric lattice Boltzmann method

The advancement of point-of-care testing (POCT) microfluidic systems critically relies on the rational design of topologically complex microchannel networks governed by multiphase flow dynamics. This study develops an approach based on the Graphics Processing Unit accelerated volumetric lattice Boltzmann method with the Shan–Chen multiphase model to investigate the droplet breakup characteristics in benchmark Y-shaped microchannels, revealing: (1) three universal stages—compression, compression-stretching, and rapid rupture (capillary dominance); (2) spatiotemporal characteristics (breakup time, T*, daughter droplet volume ratio, Vr) affected by the geometrical parameters and capillary numbers; and (3) critical transition at Cacritical=0.108 where external dominance (Ca>Cacritical) yields slight T* reduction (enhanced by deformation at Ca>0.135) with stable Vr, while internal dominance (Ca<Cacritical) causes sharp decreases in both; (4) parabolic Vr/T* vs initial position relationships showing minimal T* at the symmetric center; and (5) T* follows a parabolic law minimized at RB=0.294 ± 0.009, and Vr adheres to power-law scaling, both with angle-dependent coefficients. These insights establish essential parametric dependencies for POCT topology optimization.