Screening of sperm velocity by fluid mechanical characteristics of a cyclo-olefin polymer microfluidic sperm-sorting device

The microfluidic sperm-sorting (MFSS) device is a promising advancement for assisted reproductive technology. Previously, poly(dimethylsiloxiane) and quartz MFSS devices were developed and used for intracytoplasmic sperm injection. However, these disposable devices were not clinically suitable for assisted reproduction, so a cyclo-olefin polymer MFSS (COP-MFSS) device was developed. By micromachining, two microfluidic channels with different heights and widths (chip A: 0.3 x 0.5 mm; chip B: 0.1 x 0.6 mm) were prepared. Sorted sperm concentrations were similar in both microfluidic channels. Linear-velocity distribution using the microfluidic channel of chip B was higher than that of chip A. Using confocal fluorescence microscopy, it was found that the highest number of motile spermatozoa swam across the laminar flow at the bottom of the microfluidic channel. The time required to swim across the laminar flow was longer at the bottom and top of the microfluidic channels than in the middle because of the low fluid velocity. These results experimentally demonstrated that the width of microfluidic channels should be increased in the region of laminar flow from the semen inlet to the outlet for unsorted spermatozoa to selectively recover spermatozoa with high linear velocity

Application of a numerical simulation to improve the separation efficiency of a sperm sorter

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

Numerical simulations of blood cell flow in non-Newtonian fluid

We investigated how non-Newtonian viscosity behavior affects the flow characteristics of blood cells. Our findings offer insight about how shear thinning affects the dispersion of liposome-encapsulated hemoglobin and red blood cells in blood. The lattice Boltzmann method was used for fluid calculations, and the rheological properties of the non-Newtonian fluid were modeled with power-law relationships. The deformable three-dimensional red blood cell model was applied. First, we investigated the effects of shear thinning on the flow behavior of single blood cell. Simulation results indicate that shear thinning promotes the axial concentration of red blood cells. Next, varied the hematocrit to see how mutual interference between blood cells affects flow. At low hematocrit, shear thinning clearly promotes the axial concentration of red blood cells. As the hematocrit increases, in contrast, mutual interference has a greater effect, which counteracts shear thinning so the red blood cell distribution resembles the distribution within a Newtonian fluid

Numerical simulations of blood cell flow in non-Newtonian fluid

We investigated how non-Newtonian viscosity behavior affects the flow characteristics of blood cells. Our findings offer insight about how shear thinning affects the dispersion of liposome-encapsulated hemoglobin and red blood cells in blood. The lattice Boltzmann method was used for fluid calculations, and the rheological properties of the non-Newtonian fluid were modeled with power-law relationships. The deformable three-dimensional red blood cell model was applied. First, we investigated the effects of shear thinning on the flow behavior of single blood cell. Simulation results indicate that shear thinning promotes the axial concentration of red blood cells. Next, varied the hematocrit to see how mutual interference between blood cells affects flow. At low hematocrit, shear thinning clearly promotes the axial concentration of red blood cells. As the hematocrit increases, in contrast, mutual interference has a greater effect, which counteracts shear thinning so the red blood cell distribution resembles the distribution within a Newtonian fluid