Lab-on-a-chip counts and sorts sperm
By Ben Coxworth
October 31, 2011
While just about everyone is familiar with home pregnancy testing kits, what many of us may not realize is that a (sort of) equivalent product exists for men - home sperm count kits. These kits, however, will simply tell users if their sperm count is above or below a standard value. While a yes or no answer like that might suffice for the pregnancy kits, a little more information would definitely help a man who suspects he might be infertile. Loes Segerink, a PhD student from The Netherlands' University of Twente, hopes to change that with this prototype lab-on-a-chip device. Segerink's chip counts exactly how many sperm are present in a sample of ejaculate, and can even differentiate between the good swimmers and the duds.
In Segerink's chip, sperm are caused to flow through a liquid-filled channel, passing beneath electrode bridges. As cells of any type pass below those bridges, it causes a brief fluctuation in the electrode's electrical resistance. When tested, the system was able to tell the difference between sperm, white blood cells, and introduced microspheres.
By counting the number of sperm-specific fluctuations, the chip determines the number of sperm in the sample - a one-milliliter sample should contain at least 20 million of them. The system also keeps track of the number of white blood cells, which is an indicator of sperm quality.
Additionally, by making a small adjustment, users can separate motile and non-motile sperm, then count them separately. This is of particular importance, as having a relatively high sperm count doesn't count for much if most of those sperm are defective.
Segerink is now in the process of setting up a company to refine the U Twente chip, and commercially develop an accompanying read-out device that will incorporate it.