On a hunch, I was curious if copper or silver can fuck with (murder) sperm like it can with pathogenic cells. Supposedly that's actually how the copper IUD contraceptive works. Somehow I never realized that connection until just now.

Doubt there'd be a viable way for that to work from the guy's end though, since copper's effects on cells usually requires at least a few minutes to a few hours of contact, which makes it far more viable at "repelling" sperm from the uterus than murdering it outright during transmission.