If you've ever worried about the environmental impact of all those discarded latex condoms, this might be the super-futuristic invention for you! Australian scientists have apparently figured out how to insert a microchip in the vas deferens (that's the part of the male equipment that delivers semen), and when the man is about to have sex, he can press "pause" on a device that sends RF waves to his intimate microchip. The chip translates the waves into acoustic waves, which then cause the chip to expand, blocking sperm from coming out.
source
source