Straining Flow Effects on Sperm Flagellar Energetics in Microfluidic Cross‐Slot Traps

Sperm need to effectively navigate the intricate pathways of the female reproductive tract, which are filled with various complex fluid flows. Despite numerous population-based studies, the effects of flow on the flagellar beating pattern of individual sperm remain poorly understood. In this study, a microfluidic cross-slot trap is employed to immobilize individual motile sperm for an extended period without physical tethering, thereby reducing potential cell damage and movement restriction compared to the conventional head-tethering method. The impact of pure straining flow on trapped single sperm is investigated. The experimental results demonstrate that at strain rates of 11.33 s^-1 and higher, the periodic and repetitive beating pattern of the sperm flagellum changes to irregular movement. Furthermore, an increase in strain rate from 1.89 to 11.33 s^-1 leads to a 35.4% reduction in beating amplitude and a 41.2% decrease in hydrodynamic power dissipation. These findings underscore the capability of the microfluidic cross-slot platform to trap sperm with high stability, contributing to a better understanding of sperm behavior in response to fluid flows.