Investigating the separation and sorting of high-quality sperm in spiral microchannels using the Dean flow regime

Infertility is a growing global issue that affects millions of couples, posing significant challenges to personal and societal well-being. This study explores a novel approach to separating and sorting high-quality sperm using spiral microchannels to enhance assisted reproductive technologies (ART). We developed a spiral microchannel that utilizes inertial microfluidics and Dean flow to effectively separate sperm based on motility and morphology. The microchannel was fabricated using CO₂ laser engraving, resulting in a spiral design with a width of 0.35 mm, a total radius of 18.5 mm, and a depth of 0.2 mm. In a series of experiments, semen samples were injected at varying flow rates (ranging from 0.5 to 2 ml/min) to determine the optimal conditions for separating motile sperm from non-motile sperm. The results indicated that increasing the flow rates significantly improved separation efficiency. The formation of Dean's vortices directed motile sperm toward the inner wall of the channel, while immotile sperm and solid particles were directed toward the inner wall. Notably, at a flow rate of 1.3 ml/min, the separation rate improved significantly, demonstrating the effectiveness of this microfluidic approach in yielding a higher quantity of viable sperm with less DNA damage while preserving sperm integrity as quantified by the Sperm Retrieval Index (SRI) with up to 4.5 fold improvement over baselines per World Health Organization standards. This innovative method holds promise as a valuable supplement to conventional ART techniques, offering scalability and reduced processing time. Sperm DNA fragmentation assays at select rates (0.5, 1.3, and 2 mL/min) confirmed the channel's superiority in minimizing damage relative to raw samples, likely attributable to diminished reactive oxygen species exposure. This label-free, scalable method serves as an efficacious adjunct to traditional ART protocols, curtailing processing duration and oxidative stress while enhancing clinical applicability for routine infertility management.