We bring out a passive droplet sorting perspective engendered by emulsion flow in a parallel microchannel with converging–diverging branches and varying channel constriction ratios (CR) and throat lengths (TL). In one microdevice, the value of TL in both the branches was fixed at 300 $\mathrm{\mu }$m, while the CR were varied between 0.50 and 0.75. The other microdevice had a constant CR of 0.50, but the TL was changed between 300 $\mathrm{\mu }$m and 600 $\mathrm{\mu }$m. Three different emulsions containing mean droplet sizes of 25.65 $\mathrm{\mu }$m, 36.72 $\mathrm{\mu }$m, and 39.18 $\mathrm{\mu }$m are analyzed at three different flow rates of 2 $\mathrm{\mu }$l/min, 10 $\mathrm{\mu }$l/min, and 30 $\mathrm{\mu }$l/min. Depending on the difference in geometric constriction induced flow resistances in two arms, bigger droplets are observed to flow through the less resistive path and smaller droplets move across the other branch. Our results demonstrate that droplet sorting efficacy can be more effectively tuned with constriction ratio instead of the throat length variation keeping other geometric and rheological properties constant. Moreover, droplet separation is found to be facilitated by decreasing the emulsion flow rate and increasing the dispersed phase viscosity from 20 cSt to 350 cSt.

我们提出了由乳液在平行微通道中流动产生的被动液滴分选视角，该微通道具有收敛-发散分支和不同的通道收缩率 (CR) 和喉部长度 (TL)。在一个微型器件中，两个分支的 TL 值都固定为 300$\mathrm{\mu }$m，而 CR 在 0.50 和 0.75 之间变化。另一个微型器件的 CR 恒定为 0.50，但 TL 在 300 之间变化$\mathrm{\mu }$米和600$\mathrm{\mu }$米。三种不同的乳液，平均液滴大小为 25.65$\mathrm{\mu }$米，36.72$\mathrm{\mu }$米和 39.18$\mathrm{\mu }$m 在三种不同的流速下进行分析 2$\mathrm{\mu }$升/分钟，10$\mathrm{\mu }$升/分钟和 30$\mathrm{\mu }$升/分钟。根据两个臂中几何收缩引起的流动阻力的差异，观察到较大的液滴流过阻力较小的路径，而较小的液滴则穿过另一个分支。我们的结果表明，液滴分选效率可以通过收缩比而不是喉长变化来更有效地调整，从而保持其他几何和流变特性不变。此外，发现通过降低乳液流速和将分散相粘度从 20 cSt 增加到 350 cSt 可以促进液滴分离。