Fig. 2.

CFD simulation of the crescent shape diffuser zone and schematic explanation of the motile sperm sorting mechanism. (A) Vector image of the countercurrent flow. (B) Vector image without the frame line from the different viewpoint from A. (C) Flow rate magnitude distribution image. Same magnitude color scale is used in A–C. Higher magnitude is indicated by red, whereas lower magnitude is indicated by dark blue. (D) Schematic showing the fluid flow and sperm sorting mechanism. Motile spermatozoa swim upstream at both sides of the diffuser zone and throughout the whole diffuser area and migrate to the center area near the mouth leading to multiple channels. Moribund spermatozoa are pushed back to chamber B, whereas motile spermatozoa are induced by rheotactic property to swim upstream and migrate along the microchannel.