A tunable high-gradient magnetic separation system based on an ordered wire-array column

Upstream sample preparation often limits the sensitivity and reproducibility of bioanalysis, particularly for rare or weakly magnetic targets. Here, we present a tunable high-gradient magnetic separation system based on an ordered Fe-Ni wire-array column, which generates stable and quantifiable local high-gradient regions under a uniform external magnetic field. The magnetic flux density (B) and volumetric flow rate (Q) can be independently adjusted, allowing separation conditions to be systematically regulated and interpreted using the Mason number (Mn). Using magnetically homogeneous metHb-RBCs and heterogeneous SPION-labeled RAW264.7 macrophages as model systems, we demonstrate tunable capture and enrichment behavior under different magnetic-field and flow-rate conditions. For metHb-RBCs, near-equal Mn conditions produced comparable captured-cell fractions across different B-Q combinations, supporting the use of Mn as a force-flow descriptor for weak and relatively homogeneous magnetic cells. For SPION-labeled RAW264.7 macrophages, OTMS-derived single-cell magnetic moment distributions showed preferential enrichment of higher-moment cells, while near-matched apparent Mn conditions gave similar enrichment trends despite pronounced magnetic heterogeneity. These results show that the ordered wire-array column provides a geometry-defined and quantitatively interpretable HGMS microenvironment for magnetic cell enrichment. The system may also provide a useful basis for future studies on other magnetic targets.