Sperm-Powered Micro-Robots Could Offer a New Method of Fertilization

It's cool when robots mimic the biological world, but it's possibly even cooler when the two combine to make awesome robot-biology hybrids. Scientists in Germany have made the first “spermbot”—a micro-bio-robot powered by sperm, which could lead to a new fertilization method.

Biobots, or biological robots, consist of biological matter programmed to behave a certain way. The spermbot (or “sperm-flagella driven micro-bio-robot," as it’s officially called) is the first biobot to use sperm cells. Each bot is essentially a single sperm with its head trapped inside a tiny metallic tube; when it swims, it pushes the tube forward. As the tube is magnetic, the bot's direction can be controlled using magnetic fields, and one future application could be to usher individual sperm to an egg.

In a paper published this month in the journal Advanced Materials, the researchers explained that creating bots for biomedical applications is difficult because some sort of micromotor is generally needed to power them. Artificial motors, however, need some kind of fuel, which is often toxic to the human body: “Hence, a next generation of self-propelled microdevices is desperately sought after.”

A sperm’s flagellum—the tail-like bit that propels it forward—makes for a perfect all-natural biomotor. Oliver Schmidt, one of the paper’s authors, told New Scientist that sperm was an ideal solution as it's harmless to the human body, doesn’t require an external power source, and can swim through viscous liquids—which is, after all, where sperm cells usually find themselves.

To make the spermbot, the researchers built microtubes just 50 microns long out of titanium and iron nanoparticles. One end was wider than the other, so when a sperm cell swam into the wider end, its head would get stuck as the tube tapered. They used bovine sperm for their tests, as it's close in size and shape to human sperm.

To control the bot, they simply had to adjust the external magnetic fields by moving a neodymium magnet over it, and it would spin around like a compass needle. They could also vary the spermbot’s speed, as sperm travel faster in higher temperatures.

The authors wrote that the micro-bio-robots could be used for “a medical application that involves the controlled guidance of a single sperm cell to an egg cell.” This could be done in vivo—not in a test tube. Another application for the technology could be targeted drug delivery, as the tiny bots can be directed to exactly where they're needed. It's a great example of biology and technology working together to solve problems neither can fix alone.