Springer US Acta Medica Okayama 1387-2176 11 1 2009 Application of a numerical simulation to improve the separation efficiency of a sperm sorter 25 33 EN Toru Hyakutake Yuki Hashimoto Shinichiro Yanase Koji Matsuura Keiji Naruse This paper describes a study in which numerical simulations were applied to improve the separation efficiency of a microfluidic-based sperm sorter. Initially, the motion of 31 sperm were modeled as a sinusoidal wave. The modeled sperm were expected to move while vibrating in the fluid within the microchannel. In this analysis, the number of sperm extracted at the outlet channel and the rate of movement of the highly motile sperm were obtained for a wide range of flow velocities within the microchannel. By varying the channel height, and the width and the position of the sperm-inlet channel, we confirmed that the separation efficiency was highly dependent on the fluid velocity within the channel. These results will be valuable for improving the device configuration, and might help to realize further improvements in efficiency in the future. No potential conflict of interest relevant to this article was reported.