Adaptive surface sensing enables mammalian sperm navigation in complex environments

During transit through the fallopian tube of the female reproductive tract, sperm encounter a structurally complex lattice-like environment characterized by confinement and curvature created by the folded epithelium of the fallopian tube. To replicate these conditions, we examined sperm scattering and migratory behavior in microfabricated obstacle lattices with varying spacing. We found a passive adaptive sensing mechanism that regulates sperm surface interactions in confined and curved environments. Specifically, scattering dynamics, including the collision angle, were impacted as sperm navigated the lattice, and surface interaction times were reduced under more confined conditions. A mathematical model was developed to describe sperm transport in these structured landscapes, predicting up to a nine-fold enhancement of diffusivity compared to free swimming sperm. Hyperactivated sperm displayed similar adaptive behavior within the lattice. We found that sperm dynamically adjust their navigation strategy in response to environmental geometry, allowing efficient migration despite confinement. More broadly, the study highlights how physical structure modulates microswimmer behavior and provides new insight into the physical processes that govern sperm navigation and the mechanisms underlying mammalian fertilization.