River meander-inspired cross-section in 3D-printed helical microchannels for inertial focusing and enrichment

Traditional microfluidic cross-sections are limited to several common geometries, which seriously imposes restrictions on the studies of flow fields and particle manipulations in microchannels. Fortunately, 3D printing technique is a versatile tool which can realize one-step fabrication of helical microchannels with various geometries and parameters. Inspired by the bed topography in river meanders, here, we report a novel 3D-printed river meander-like cross-section in helical microchannels for size-based inertial focusing and enrichment, aiming to realize more functional geometries as well as reduce the extensive laborious requirement in traditional fabrication process. This device can facilitate particle focusing at a larger scale than traditional channels. Compared to the circular, rectangular and trapezoidal channels, the river meander-like microfluidic channel can successfully realize 26 mu m particle focusing with a thinner focusing band in a shorter channel length. Also, in a single test, this structure can achieve 85.4% recovery and the enrichment ratio of 1.86 of spiked MDA-MB-231 cells in the whole blood, overcoming the dependence on traditional cell manipulation microfluidic devices. These results indicate that this 3D-printed river meander-like microfluidic chip has the great potential of size-based cell/particle sorting and enrichment for clinical application.