The Electric Border Collie

Using electric fields, researchers are learning to herd microbes for the benefit of astronauts and Homeland Security.
For thousands of years, humans have been herding. Goats. Sheep. Cattle. It's not always easy, and modern ranchers usually have help. They use a Border Collie to keep their beasts together. These dogs are amazing; if they can see it, they can herd it.
But what do you do if you want to herd, say, microbes?
It's not as silly as it sounds. Onboard a spaceship, for instance, a few microbes floating in the ship's drinking supply could be a harbinger of trouble to come. The same is true of urban water supplies. What if terrorists dump pathogens into a city reservoir? Herding microbes together for testing and eradication could save the day.
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Researchers at Texas A&M University are working on a prototype device, a sort of electric Border Collie, that might be able to herd microbes and run to the rescue! The principle is simple: the cell membranes of some pathogens are negatively charged. Electric fields, therefore, could be used to corral the tiny beasts.
Conventional microbe detectors work with very small volumes of water, usually between 10 and 50 millionths of a liter. That can be a problem: If dangerous microbes are widely dispersed in the water supply-as they might be in the early stages of infestation-the odds of finding microbes in such a tiny sample are poor. Choosing a sample to test that contains the harmful microbe is a hit-or-miss proposition.
"The biggest roadblock for any agency - whether it's Homeland Security or for NASA or for EPA or anybody else - is to monitor a large quantity of water [for small numbers of microbes]," notes Suresh Pillai of Texas A&M.
Pillai and and his collaborator, Texas A&M engineering professor Ali Beskok, have recently received a grant from NASA's Office of Biological and Physical Research to solve this problem.