A micro- and nano-fluidic device stacked with magnetic beads is developed to efficiently trap, concentrate, and retrieve Escherichia coli (E. coli) from bacteria suspension
and pig plasma. The small voids between the magnetic beads are used to physically isolate the bacteria in the device. We use computational fluid dynamics (CFD), 3D
tomography technology, and machine learning to probe and explain the bead stacking in a small 3D space with various flow rates. A combination of beads with different sizes is utilized to achieve a high capture efficiency of ~86% with a flow rate of 50 μL/min. Leveraging the high deformability of this device, the E. coli sample is retrieved from the designated bacteria suspension by applying a higher flow rate, followed by rapid magnetic separation. This unique function is also utilized to concentrate E. coli from the original bacteria suspension. An on-chip concentration
factor of ~11× is achieved by inputting 1,300 μL of the E. coli sample and then concentrating it in 100 μL buffer.
Importantly, this multiplexed, miniaturized, inexpensive, and transparent device is easy to fabricate and operate, making it ideal for pathogen separation in both laboratory and pointof- care (POC) settings.