COULD zapping testicles with ultrasound provide a cheap, non-invasive alternative to vasectomy? It’s just one of 78 offbeat ideas that won a $100,000 grant from the Bill and Melinda Gates Foundation on 10 May.

The aim of the Grand Challenges scheme is to encourage unconventional thinking to improve health in developing countries. Other ideas to receive funding include carnivorous plants that eat mosquitoes to combat malaria, and using a “seek and destroy” laser-based vaccine to fight the disease leishmaniasis.

The idea of using ultrasound as a contraceptive comes from James Tsuruta and Paul Dayton of the University of …