Here’s a novel idea for treating infertility caused by poor-swimming sperm: Attach a motor to them. In an article published in the American Chemical Society journal Nano Letters, researchers describe the “spermbot”—a metal helix controlled by a rotating magnetic field that can wrap around a sperm’s tail and propel it through a fluid chamber. The helix then reverses its direction to release the sperm once it lodges in the wall of an egg (see video, above). If the strategy can be perfected in the human fallopian tube, it might allow some couples to conceive with artificial insemination rather than the more complex and costly in vitro fertilization, where eggs are removed and fertilized in a dish. The strategy would require sophisticated imaging to track the sperm and guide it inside the body. But the team has a more fundamental problem to deal with first: The little motors sometimes get stuck to the sperm tails and won’t relinquish their cargo.