Microfluidic cross-slot trapping to study single sperm under straining flow

Approximately one in six couples worldwide experiences infertility, with male factors solely contributing to 30% of these cases. A significant yet poorly understood phenomenon involves how sperm cells navigate the complex pathways of the female reproductive tract, encountering diverse fluid flow conditions. Thus, gaining a deeper understanding of the individual characteristics of sperm is crucial for advancing infertility management. However, due to their constant motion, analysing sperm presents a significant challenge. One common practice involves tethering individual sperm heads to slides, despite the risk of cell damage. In this study, we enhanced the microfluidic cross-slot trap design to immobilize individual sperm without physical tethering, ensuring long residence time with high stability in a minimally invasive environment. This platform provides uniform extensional flow and strain rate, making it a promising system for investigating the behaviour of single sperm in response to fluid flow. We subjected trapped sperm to different strain rates to examine the effect of strain rate on sperm flagellar beating patterns. Consequently, this advanced microfluidic device offers an effective platform for analysing the behaviours of individual sperm.