About 30-50% of clinical infertility cases occur because of a malefactor with sperm defects. Sperm parameters including extremely low sperm concentration, poor sperm motility, and abnormal morphology, hormonal disturbances, and physical and psychological problems may contribute to natural fertility problems.
Earlier, these abnormalities were not completely overcome by contemporary infertility treatments such as intrauterine insemination and conventional in vitro fertilization (IVF), but the advent of intracytoplasmic sperm injection (ICSI) in the early 1990s has allowed patients with oligozoospermia or azoospermia to father children. ICSI enables the fertilization of an egg with one sperm selected from ejaculated spermatozoa. Therefore, sperm quality parameters, including motility, morphology, viability, DNA integrity, apoptosis, and maturity, are the critical determinants of successful assisted reproductive techniques (ART) outcomes. Several methods such as double-density centrifugation and conventional swim-up procedure are performed for the isolation and the collection of the high-motility spermatozoa from semen samples and removing any impurities that interfere with fertilization.
However, several studies found that single or multiple centrifugation steps induce sperm DNA damage and the generation of reactive oxygen species (ROS) producing adverse consequences during the post-implantation development of the embryo rather than before it. Therefore, there is a need to develop a sperm separation technique that facilitates the retrieval of spermatozoa with normal DNA integrity from ejaculated semen. Microfluidic technology was introduced into this field at the beginning of the 21st century. Studies have reported that conventional semen processing techniques have adverse effects on sperm deoxyribonucleic acid (DNA) integrity leading to decreased pregnancy rates and are also associated with potential pro mutagenic alterations to sperm DNA. A gravity-driven microfluidic device, on the other hand, isolates motile sperms with good DNA integrity from seminal plasma, dead sperm, and debris, using microscale laminar flow without centrifugation.