Johns Hopkins Engineers Use Pockets of Vapor to Push Liquids through Micro Devices
Many researchers are racing to develop miniature high-tech devices each smaller than a postage stamp to treat medical conditions, test new drugs and monitor pollutants. All of these require a tiny pump that can repeatedly and reliably push small amounts of liquid through narrow channels for rapid analysis.
To accomplish this, engineers at The Johns Hopkins University have invented a micropump powered by the repeated growth and collapse of a single bubble. Because the bubble is generated by heat, it is easy to control, the inventors say. And because the bubble-powered pump has no moving mechanical parts, it is unlikely to wear out too quickly.
"It's very different from having a pump with a valve that has to open and close any number of times," says Andrea Prosperetti, the university's Charles A. Miller Jr. Distinguished Professor of Mechanical Engineering. "With no moving parts, the bubble-powered pump's prospects of failure are minimal."
Prosperetti, an internationally respected expert on the physics of bubbles, worked with two other Johns Hopkins mechanical engineering researchers in his lab, Hasan Oguz and He Yuan, to design, build and test a prototype bubble-based pump. They presented their results at recent conferences sponsored by the Acoustical Society of America and the Defense Advanced Research Projects Agency.
The team's prototype utilizes two main tubes. One is 1.6 millimeters wide, about
the width of the wire used to make a large paperclip. The other tube is half
that diameter, but the inventors say the same principles would apply to smaller
tubes as well. The prototype's main tubes are connected by an even narrower
passage or "throat," measuring 0.5 millimeters in diameter. The engineers
inserted steel needles into each of the larger tubes, connected the needles to a
power source and filled the tubes with a salt solution to complet
Contact: Phil Sneiderman
Johns Hopkins University