Figure 5
Schematic showing passive sperm reorientation.
Sperm flagellum is approximated by a chiral helix with a conical envelope. In fluid flow, sperm swims with an angle to the flow streamline. The chirality and imbalance of hydrodynamic force on posterior and anterior flagellum produce a net lift force, which is opposed by the drag force on sperm, resulting in a torque reorienting sperm upstream.
