Microfluidic
technologies enabling the control of secondary flow
are essential for the successful separation of blood cells, a process
that is beneficial for a wide range of medical research and clinical
diagnostics. Herein, we introduce a dimension-confined microfluidic
device featuring a double-spiral channel designed to regulate secondary
flows, thereby enabling high-throughput isolation of blood for plasma
extraction. By integrating a sequence of micro-obstacles within the
double-spiral microchannels, the stable and enhanced Dean-like secondary
flow across each loop can be generated. This setup consequently prompts
particles of varying diameters (3, 7, 10, and 15 μm) to form
different focusing states. Crucially, this system is capable of effectively
separating blood cells of different sizes with a cell throughput of
(2.63–3.36) × 108 cells/min. The concentration
of blood cells in outlet 2 increased 3-fold, from 1.46 × 108 to 4.37 × 108, while the number of cells,
including platelets, exported from outlets 1 and 3 decreased by a
factor of 608. The engineering approach manipulating secondary flow
for plasma extraction points to simplicity in fabrication, ease of
operation, insensitivity to cell size, high throughput, and separation
efficiency, which has potential utility in propelling the development
of miniaturized diagnostic devices in the field of biomedical science.