A Pump-Free, Magnetorheological-Elastomer-Driven Oscillatory Microfluidic Device for Cell Manipulation

Controlling microscale and nanoscale biological sample motion within microfluidic channels is essential for bioanalysis and diagnostics, yet most existing systems depend on external pumps or complex on-chip actuators that limit their portability and biocompatibility. Here, we present a pump-free, magnetorheological-elastomer (MRE)-driven oscillatory microfluidic (PMOM) device that consists of a rotor with permanent magnets and a microfluidic channel with partially functionalized MRE. A soft, deformable MRE membrane is actuated by the presence and absence of magnetic fields induced by the rotating magnets and then drives the flow to move back and forth in the microchannel. The single-layer design features a straightforward fabrication process and achieves stable oscillatory flow without pumps, valves, or electrodes. The PMOM device enables the ultralow blockage-ratio (β = 0.0047) particle focusing, efficient size-dependent separation of blood and cancer cells, and oscillatory shear-induced platelet activation under physiological shear levels. Moreover, nanoscale extracellular vesicles (∼270 nm) were successfully concentrated along the channel centerline, confirming the capability of the system to manipulate biological nanoparticles without sheath flow and a high-precision pump. By combining simple fabrication, strong biocompatibility, and tunable oscillatory actuation, this platform establishes an approach for pump-free elasto-inertial microfluidics and opens windows for micro/nanoscale manipulation and mechanobiological studies.