Inertial microfluidics is promising for the high throughput, label-free continuous separation of multicomponent microparticles. However, conventional single spiral microchannels struggle to separate three or more particle types, while traditional cascaded systems relying on sheath fluids or multiple pumps suffer from increased operational complexity. To address this, we propose a cascaded dual spiral microfluidic chip based on passive flow resistance matching. Driven by a single syringe pump without sheath flow, it achieves continuous sorting of three particle types. An adaptive flow resistance network is incorporated: the first stage channel maintains high velocity to preferentially extract large particles via strong inertial lift forces. The fluid then enters the second stage through a predetermined geometric resistance for automatic deceleration. Experiments demonstrate that at 1.6 mL/min, the system achieves continuous separation of a 1:10:10 mixture of 15, 10, and 5 µm microparticles. The 15 µm target recovery rate reaches 92%, while the collection purities for 10 µm and 5 µm particles exceed 98% and 99%, respectively. This purely passive fluidic architecture simplifies cascaded sorting, providing a robust engineering solution for complex multicomponent sample preprocessing.
Zhang et al. (2026) studied this question.