Analysis of a swimming sperm in a shear flow

Microfluidic devices exhibit many attractive characteristics for separation of motile sperms from the non-motile ones. The motility of swimming sperms is critical to a successful fertilization. In this paper, we examine the shear effect of microfluidic flow on a swimming sperm. We employ the resistive force theory to compute the hydrodynamic forces acting along the flagellum of the sperm and investigate the beating pattern of the flagellum as well as the sperm’s swimming velocity. We found that the shape of the flagellum is significantly affected by high shear rate which in turn affects the swimming velocity. Both negative and positive shear rates contribute to a higher swimming velocity of the sperm, and the effects of negative and positive shear rates can only be distinguished at high sperm number. Furthermore, we found that sperms with smaller heads swim faster. Our findings here can be applied to enhance performance of sperm separation and sorting devices.