It couldn't be simpler. Just take a length of stiff but bendable tubing and connect the ends with a short piece of more flexible pipe to form a loop. Before you seal the loop, fill the tubes with water―perhaps laced with some drops of coloured oil so you can see any flow. Now rhythmically squeeze and release the flexible section and watch what happens to the fluid. Bizarrely, it will begin to move around the circuit. The phenomenon has been known for centuries. But nobody understands how such a crude arrangement can possibly get fluid moving round the circuit without a valve to stop it flowing backwards between compressions. It's a puzzle that has a bearing on a range of problems, from how to build microscopic "labs on a chip" to improving first aid for heart-attack victims. Now mathematician Eunok Jung is trying to solve it. She began her quest while a graduate student at New York University. Working with her supervisor, Charles Peskin, she developed a computer program that simulates a basic "valveless pump". For simplicity's sake they made their virtual fluid circuit two-dimensional, rather like an oval racetrack. The program computed the intricate details of what happens to the fluid and the walls of the tube as one end of the flexible segment is rhythmically squeezed and released. Running the simulation took several hours on a high-powered workstation, but in the end it came up with the hoped-for result: the fluid coursed around the circuit.
展开▼
