Last January, an Australian engineer announced a bizarre new contraceptive for men: a radio-controlled implant that could block the flow of sperm with the click of a button. The device, which is still in the conceptual stages, is the latest in a growing number of experimental male birth-control methods—including sperm plugs, sperm dissolvers and heat-inducing gels—that don’t tinker with testosterone.

Although 55 percent of men are willing to carry the burden of contraception, no method exists between the two extremes: condoms (which fail an estimated 15 percent of the time) and vasectomy (an invasive procedure that’s difficult to reverse). Even less appealing may be the much-discussed male “pill,” still in clinical trials, which shuts down hormone production in the hypothalamus and requires monthly shots of testosterone to restore it. And although women have been using hormones to control fertility for years, less is known about the long-term effects of hormone disruption in men.

As an alternative, many of the new sperm stoppers that are in the works target the vas deferens, the tube along which sperm travel. The idea is to stop sperm at one localized site, rather than using hormones that can affect heart function, weight and cholesterol levels. Launch the gallery to see how they work.