One futuristic approach (which has already been adopted by some of the more primitive insects) is to do away with the hundreds of millions of sperm, and rely on just one to get the job done. If you’re going to do that, your one sperm needs to be incredibly awesome, and thanks to science, it can be. Researchers from the Institute for Integrative Nanosciences at IFW Dresden in Germany have successfully tested tiny, magnetically-driven power suits for individual sperm that can turn them into steerable cyborg “spermbots” that can be remote controlled all the way to the egg.
To be slightly more serious about things, spermbots are intended to help deal with one of the primary causes of infertility: sperm that for whatever reason have poor mobility, but are otherwise perfectly healthy. Techniques like artificial insemination or in vitro fertilization can help, but they tend to be expensive and not very reliable, since there’s a chance for failure at many points during the multiple-step process. The fundamental problem that needs to be solved is this: how do you get one single healthy sperm to fertilize an egg? The IFW Dresden researchers came up with what has to be the simplest and most straightforward approach, which is to give the sperm and motor and just drive it there yourself:
The motors are metal-coated polymer microhelices that are sized such that they’ll fit over the tail of an individual sperm. A rotating magnetic field causes them to spin, propelling them (and whatever sperm they’re attached to) forward. Adjusting the orientation of the field can steer the spermbots in 3D, and all of this stuff can be done inside of an MRI machine, although the video (and testing so far) has been in the equivalent to a Petri dish. Once the (presumably now very very dizzy) sperm reaches the egg, the micromotor can even plow them into it, making the fertilization process as easy as possible.
There are still plenty of challenges here, but the researchers are confident that this is a useful step in the right direction. My suggestion would be to equip the robosperm with tiny little laser cannons just in case any other sperm get in its way. Pew pew!