Optimization of a microfluidic spiral channel used to separate sperm from blood cells

Assisted reproductive technology includes medical procedures that confront the problem of infertility. In some cases of male infertility, blood cells are present in the sperm containing samples and must be removed. Spiral-channel devices have been developed to perform this task, but there is a strong need to increase their throughput. In this work, the theory behind the separation is employed to optimize the device for increased throughput. An existing device that is known to separate sperm and blood cells with a rectangular cross section of 600 x 100 mu m(2) was used as the baseline. Using its physics, theoretical models were generated to explore theoretical performances of larger-size channels. The models suggested that a channel of size 800 x 133 mu m(2) would likely work. This geometry enabled the throughput to be increased by 50%, from 2 ml/min in the case of the baseline-size to 3 ml/min in the designed device. Experiments using the larger device resulted in a recovery of more than 90% of sperm cells while removing 89% of red blood cells (RBCs). In comparison, the reference device results in a 90% recovery of sperm cells while removing 74% of white blood cells (WBCs). The length of the channel was also reduced to reduce the pressure required to operate the chip. Literature has shown the removal of WBCs to be higher than that of RBCs due to their larger size, spherical shape, and comparatively low deformability, suggesting that the revised chip would be faster and better for the separation of sperm and all blood cells.