Newswise — Late one crisp night in 2006, a hospital technician in Montreal slid the limp body of an anesthetized pig into the tube of a magnetic resonance imaging machine, or MRI. A catheter extended from a large blood vessel in its neck--a carotid artery. Into the catheter, a surgeon injected an iron bead slightly larger than the ball of a ballpoint pen. In a room next door, my engineering graduate students and I held our breath. We were testing a program designed to manipulate the machine's magnetic forces that would guide the bead like a remote-controlled submarine. Or so we hoped.

On a computer screen, the bead appeared as a white, square tracking icon perched on the gray, wormlike image of the scanned artery. We stared at the square and waited. Nothing. Seconds ticked by, and still the bead refused to budge. Then suddenly the room erupted in cheers as we clapped our hands to our mouths and pointed at the screen. There, the bead was hopping up and down the artery, tagging every waypoint we had plotted. That was the first time anyone had steered an object wirelessly through the blood vessel of a living creature. The experiment convinced us we could engineer miniature machines to navigate the vast circulatory system of the human body. The microrobots would be able to travel deep inside the body, cruising our tiniest blood vessels to places that catheters can't go, performing tasks that would be impossible without invasive medical procedures.