Microscale Integrated Sperm Sorter

This chapter describes the design and fabrication of a passively driven microfluidic sperm sorter using soft lithographic microfabrication techniques. This self-contained device can separate motile sperm from nonmotile sperm and other cellular debris. The sorting system is small (coin sized) and structurally simple. It comprises two inlets; two outlets; a sorting channel; and arrays of horizontally oriented reservoirs that function as passively driven, constant-flow-rate pumps. Sperm with higher motility are sorted out from the rest of the semen samples based on their ability to swim through interfaces between adjacent laminar streams into separate streamlines, whereas the nonmotile sperm and debris remain in their initial streamlines. The device, which we call a microscale integrated sperm sorter, does not rely on any external power sources or controllers and incorporates all sample loading and sorting functions necessary to prepare high-quality sperm for in vitro fertilization. This self-contained, inexpensive, and portable device may also be useful for developing convenient sperm motility assays that can be used at the point of care or at home.