Elasto-inertial particle focusing in 3D-printed microchannels with unconventional cross sections

In this paper, elasto-inertial particle focusing in 3D-printed microchannels with unconventional cross sections was studied. A novel 3D-printed mold-removal method was proposed to fabricate the microchannels. By modifying the orifice shape of the extrusion nozzle, the microchannel molds with arbitrary cross sections could be printed using an easily accessible fused deposition modeling (FDM) printer. After the routine PDMS casting procedure, the channel molds were dissolved to produce all-PDMS microfluidic chips, thereby eliminating the complex bonding process. The mechanisms of elasto-inertial focusing in the semielliptical and triangular microchannels were explored by comparing the particle migrations in 0.3 wt% HA solution and PBS solution, and the effects of flow rate on particle focusing position and focusing width were also investigated. We found that the single-line particle focusing in the triangular microchannel was more stable and closer to the channel bottom than that in the semielliptical microchannel, which is of great value to improve the detection sensitivity of microfluidic impedance cytometer with coplanar electrodes fabricated on the channel bottom.