Label-Free Neutrophil Separation from Tracheal Secretion Using Spiral Microfluidics Channel

Neutrophils — immune cells with multilobed nuclei, regulate tracheal immunity by engulfing invading pathogens.

To separate neutrophils from tracheal secretion, begin with a spiral microfluidic channel.

The spiral channel originates from the central inlet, progressively extending and bifurcating into inner and outer wall outlets. The bifurcation channel has varying thicknesses, ensuring efficient separation. Each curved channel resembles a trapezoid, with the outer wall height greater than the inner wall's, generating a variable flow pattern.

Fill the inlet with a pre-filtered, diluted human tracheal secretion comprising mucin aggregates, neutrophils, and erythrocytes — as incidental contaminants.  Flow the sample at a specific flow rate through the spiral microchannel leading to the dispersion of the cells and aggregates.

As cells travel through the trapezoidal channel, they experience Dean drag and inertial lift forces. The interplay between these two forces creates an equilibrium, separating cells by their sizes. As a result, larger-sized neutrophils accumulate near the channel's inner wall, while erythrocytes and mucin aggregates remain near the channel's outer wall.

Finally, neutrophils move through the broader channel and get collected in the inner wall outlet.

In contrast, the narrow channel collects erythrocytes and mucin aggregates in the outer wall outlet, ensuring efficient neutrophil separation.