Revolutionizing sperm selection: A biomimetic approach using vertical temperature differences for enhanced clinical efficiency

Biochips have emerged as promising platforms capable of mimicking in vivo environments to purify motile sperm cells and reduce the damage to sperm caused by the currently common clinical centrifugal sperm separation method. Here, we introduce a biomimetic sperm separation method inspired by the temperature gradient variance observed in the female reproductive tract. This method efficiently isolates motile sperm by directing them to swim in a specific direction based on their intrinsic behavior and temperature sensitivity. Clinical trials using human samples demonstrated that the proposed vertical temperature difference device leverages the concepts of swim-up and thermotaxis to enhance both the processed sample volume and the recovery rate, surpassing traditional microfluidic devices that rely on flow fields for sperm separation. The recovered sperm concentration of our device reached two million per milliliter, and the proportion of healthy sperm reached 99 %. It can be directly utilized in clinical settings. This device improves upon current sperm selection methods used in assisted reproduction by minimizing sperm damage.