Excuse the title, but I couldn't resist. I mean how often do you get a chance to write about robotic sperm? That develop thrust? It's not my fault though! The researchers involved have named their newly created device MagnetoSperm. Apparently this was done with great glee, since the term MagnetoSperm is mentioned no fewer than fifty times in their short four page article. Yes, I am channeling my inner 12 year old today.
Researchers at the German University in Cairo, and at the University of Twente, in The Netherlands recently reported on their progress modeling the swimming motion of sperm-flagella with a microbot made of cobalt-nickel and silicon, (see picture above). The microbot swims in an oscillating magnetic field. The head of the MagnetoSperm is elliptical in shape and forms a magnetic dipole. An oscillating magnetic field causes the elliptical head to oscillate which in turn causes the flexible tail to oscillate. The oscillating tail generates the thrust that moves the entire MagnetoSperm forward. The speed of the MagnetoSperm increases with the frequency of the oscillating magnetic field from 0 to about 45 Hz. At frequencies greater than 45 Hz, MagnetoSperm can't move quickly enough to oscillate with the field, and the propulsion thrust is reduced.
Just in case you think is all just a spoof, here's a video of the little 'bot in action: http://youtu.be/msKutVAp2RU