Quantitative Magnetic Deflection Enables Continuous‐Flow Separation of Cell Subtypes

Accurate and continuous separation of cell subtypes is increasingly demanded in biomedical research, as it enables deeper exploration of phenotypic heterogeneity and disease progression. Here, we present a novel continuous-flow cell subtype separation strategy based on spatially engineered soft magnetic interfaces that generate lateral magnetic deflection fields. By harnessing the field-shaping capability of soft magnetic strips, controllable magnetic gradients were established within microfluidic channels, producing differential lateral deflection velocities among cells labeled with distinct amounts of Dynabeads—reflecting variations in membrane protein expression. Through multi-outlet collection, efficient subtype separation was achieved. The key structural parameters of the magnetic interface, including strip thickness, width, and vertical spacing from the flow channel, were systematically optimized. Optimal separation nodes at 1.5 mm, 3 mm, and 9 mm along the flow path enabled MDA-MB-231, Caco-2, and A549 cells to be categorized into four epithelial cell adhesion molecule (EpCAM) expression levels: high (H), medium (M), low (L), and negative (N). Remarkably, a post-sorting cell viability of 98.2 ± 1.3% was maintained, supporting its potential for downstream applications such as whole-blood assays and cell culture. This platform provides a continuous, label-guided microfluidic approach for precise cell subtype separation. More importantly, it offers an actionable technical insight for magnetic field fine-tuning in cell sorting: by leveraging the spatial configuration of soft magnetic materials and the interaction/superposition of multiple soft magnetic strips, complex magnetic field designs can be achieved. This design logic serves as a referable optimization strategy for researchers engaged in magnetic field precise regulation in related fields, potentially inspiring more innovations in magnetic structure design for biomedical separation applications.