Simultaneous high-throughput particle-bacteria separation and solution exchange via in-plane and out-of-plane parallelization of microfluidic centrifuges

Inertial microfluidic devices have gained attention for point-of-need (PoN) sample preparation. Yet, devices capable of simultaneous particle-bacteria solution exchange and separation are low in throughput, hindering their applicability to PoN settings. This paper introduces a microfluidic centrifuge for high-throughput solution exchange and separation of microparticles, addressing the need for processing large sample volumes at elevated flow rates. The device integrates Dean flow recirculation and inertial focusing of microparticles within 24 curved microchannels assembled in a three-layer configuration via in-plane and out-of-plane parallelization. We studied solution exchange and particle migration using singleplex and duplex samples across devices with varying curve numbers (2-curve, 8-curve, and 24-curve). Processing 5 and 10 μm microparticles at flow rates up to 16.8 ml/min achieved a solution exchange efficiency of 96.69%. In singleplex solutions, 10 and 5 μm particles selectively migrated to inner and outer outlets, demonstrating separation efficiencies of 99.7% and 90.3%, respectively. With duplex samples, sample purity was measured to be 93.4% and 98.6% for 10 and 5 μm particles collected from the inner and the outer outlets, respectively. Application of our device in biological assays was shown by performing duplex experiments where 10 μm particles were isolated from Salmonella bacterial suspension with purity of 97.8% while increasing the state-of-the-art particle solution exchange and separation throughput by 16 folds. This parallelization enabled desirable combinations of high throughput, low-cost, and scalability, without compromising efficiency and purity, paving the way for sample preparation at the PoN in the future.