Enhanced sperm isolation via bulk acoustic waves for high-throughput motility screening.

The increasing infertility rate has become a worrying global challenge in recent years. According to the report of the World Health Organization, the male factor is responsible for over half of infertility cases, which includes the lack of desirable characteristics in sperm motility, morphology, and DNA integrity. In recent years, it has been shown that clinical methods including density gradient centrifugation cause damage to sperm DNA and besides being invasive, they are costly and time-consuming. In contrast, microfluidics has been used as a promising and non-invasive approach to manipulate biological cells. Here, by using the microvortices created by the oscillation of the bubbles caused by the bulk acoustic waves, we were able to trap sperms with less motility. In contrast, the highly motile sperms overcame the force of the microvortices and were guided to the outlet pool by following the channel boundaries. As a result, over 50% and 44% improvement in sperm progressive motility and viability, respectively, as well as 40% improvement in DNA integrity, were observed in the analysis of sperms retrieved from the output pool. In addition to being fast and non-invasive, the proposed device benefits from an easy method for sperms retrieval and does not require any preprocessing of the raw sperm sample.