University of Michigan scientists have developed a new technique to sort out the swimmers from the duds in semen, which could lead to a more efficient way for men who suffer from low sperm counts to make babies.

The new sperm sorter consists of a penny-size silicon chip divided into two channels. Semen is dripped onto one side, a saline solution on the other. Where the channels meet, the healthy, or motile, sperm swim over to the saline channel, leaving the dead or slow sperm behind. The healthy sperm are then collected for in vitro fertilization.

Current methods use centrifugation, which spins the sperm at very high speed. But the technique isn’t efficient because live sperm are pelted with dead ones, causing a significant number of viable sperm to die in the separation.

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