Is it possible to artificially put a DNA sample into someone else's sperm cell? The most obvious technical challenges are artificially causing meiosis on the DNA, keeping the sperm alive, and automating the process so you get enough sperm to actually cause pregnancy.

This technology would have a lot of applications for example helping infertile couples have a child, or for blackmailing politicians and so on with a fake lovechild. You could also use it to eat someone's cum without him knowing, if you're gay. But I'm just curious about the theory.